Add DocBlock to WatchConfig (#1467)

* Add DocBlock to WatchConfig

Added a small description of the WatchConfig().
So that you can understand in the ide why you could use it.

* Update viper.go

* update viper.go

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>
Co-authored-by: Márk Sági-Kazár <sagikazarmark@users.noreply.github.com>
Co-authored-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

.editorconfig

@@ -11,5 +11,5 @@ trim_trailing_whitespace = true
 [*.go]
 indent_style = tab
 
-[{Makefile, *.mk}]
+[{Makefile,*.mk}]
 indent_style = tab

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -19,13 +19,22 @@ body:
         required: true
       - label: I am not looking for support or already pursued the available [support channels](https://github.com/spf13/viper/issues/new/choose) without success.
         required: true
+      - label: I have checked the [troubleshooting guide](https://github.com/spf13/viper/blob/master/TROUBLESHOOTING.md) for my problem, without success.
+        required: true
 - type: input
   attributes:
-    label: Version
+    label: Viper Version
     description: What version of Viper are you using?
     placeholder: 1.8.1
   validations:
     required: true
+- type: input
+  attributes:
+    label: Go Version
+    description: What version of Go are you using?
+    placeholder: "1.16"
+  validations:
+    required: true
 - type: dropdown
   attributes:
     label: Config Source

.github/ISSUE_TEMPLATE/feature_request.yaml

@@ -1,4 +1,4 @@
-name: 🚀 Feature request
+name: 🎉 Feature request
 description: Suggest an idea for Viper
 labels: [kind/enhancement]
 body:

.github/release.yml

@@ -0,0 +1,30 @@
+changelog:
+  exclude:
+    labels:
+      - release-note/ignore
+  categories:
+    - title: Exciting New Features 🎉
+      labels:
+        - kind/feature
+        - release-note/new-feature
+    - title: Enhancements 🚀
+      labels:
+        - kind/enhancement
+        - release-note/enhancement
+    - title: Bug Fixes 🐛
+      labels:
+        - kind/bug
+        - release-note/bug-fix
+    - title: Breaking Changes 🛠
+      labels:
+        - release-note/breaking-change
+    - title: Deprecations ❌
+      labels:
+        - release-note/deprecation
+    - title: Dependency Updates ⬆️
+      labels:
+        - area/dependencies
+        - release-note/dependency-update
+    - title: Other Changes
+      labels:
+        - "*"

.github/workflows/checks.yaml

@@ -0,0 +1,18 @@
+name: PR Checks
+
+on:
+  pull_request:
+    types: [opened, labeled, unlabeled, synchronize]
+
+jobs:
+  release-label:
+    name: Release note label
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check minimum labels
+        uses: mheap/github-action-required-labels@v3
+        with:
+          mode: minimum
+          count: 1
+          labels: "release-note/ignore, kind/feature, release-note/new-feature, kind/enhancement, release-note/enhancement, kind/bug, release-note/bug-fix, release-note/breaking-change, release-note/deprecation, area/dependencies, release-note/dependency-update"

.github/workflows/ci.yaml

@@ -0,0 +1,85 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - goos: js
+            goarch: wasm
+          - goos: aix
+            goarch: ppc64
+
+    steps:
+      - name: Set up Go
+        uses: actions/setup-go@v3
+        with:
+          go-version: 1.19
+
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Build
+        run: go build .
+        env:
+          GOOS: ${{ matrix.goos }}
+          GOARCH: ${{ matrix.goarch }}
+
+  test:
+    name: Test
+    runs-on: ${{ matrix.os }}
+    strategy:
+      # Fail fast is disabled because there are Go version specific features and tests
+      # that should be able to fail independently.
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        go: ['1.17', '1.18', '1.19']
+    env:
+      GOFLAGS: -mod=readonly
+
+    steps:
+      - name: Set up Go
+        uses: actions/setup-go@v3
+        with:
+          go-version: ${{ matrix.go }}
+
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Test
+        run: go test -race -v ./...
+        if: runner.os != 'Windows'
+
+      - name: Test (without race detector)
+        run: go test -v ./...
+        if: runner.os == 'Windows'
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    env:
+      GOFLAGS: -mod=readonly
+
+    steps:
+      - name: Set up Go
+        uses: actions/setup-go@v3
+        with:
+          go-version: 1.19
+
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Lint
+        uses: golangci/golangci-lint-action@v3
+        with:
+          version: v1.50.1

.github/workflows/ci.yml

@@ -1,35 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches:
-      - master
-  pull_request:
-
-jobs:
-  build:
-    name: Build
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        os: [ubuntu-latest, macos-latest]
-        go: ['1.14', '1.15', '1.16']
-    env:
-      VERBOSE: 1
-      GOFLAGS: -mod=readonly
-      GOPROXY: https://proxy.golang.org
-
-    steps:
-      - name: Set up Go
-        uses: actions/setup-go@v2
-        with:
-          go-version: ${{ matrix.go }}
-
-      - name: Checkout code
-        uses: actions/checkout@v2
-
-      - name: Lint
-        run: make lint
-
-      - name: Test
-        run: make test

.github/workflows/codeql-analysis.yaml

@@ -0,0 +1,72 @@
+# For most projects, this workflow file will not need changing; you simply need
+# to commit it to your repository.
+#
+# You may wish to alter this file to override the set of languages analyzed,
+# or to provide custom queries or build logic.
+#
+# ******** NOTE ********
+# We have attempted to detect the languages in your repository. Please check
+# the `language` matrix defined below to confirm you have the correct set of
+# supported CodeQL languages.
+#
+name: "CodeQL"
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [ master ]
+  schedule:
+    - cron: '22 16 * * 3'
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [ 'go' ]
+        # CodeQL supports [ 'cpp', 'csharp', 'go', 'java', 'javascript', 'python' ]
+        # Learn more:
+        # https://docs.github.com/en/free-pro-team@latest/github/finding-security-vulnerabilities-and-errors-in-your-code/configuring-code-scanning#changing-the-languages-that-are-analyzed
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v3
+
+    # Initializes the CodeQL tools for scanning.
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v2
+      with:
+        languages: ${{ matrix.language }}
+        # If you wish to specify custom queries, you can do so here or in a config file.
+        # By default, queries listed here will override any specified in a config file.
+        # Prefix the list here with "+" to use these queries and those in the config file.
+        # queries: ./path/to/local/query, your-org/your-repo/queries@main
+
+    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
+    # If this step fails, then you should remove it and run the build manually (see below)
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@v2
+
+    # ℹ️ Command-line programs to run using the OS shell.
+    # 📚 https://git.io/JvXDl
+
+    # ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
+    #    and modify them (or add more) to build your code if your project
+    #    uses a compiled language
+
+    #- run: |
+    #   make bootstrap
+    #   make release
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v2
+

.github/workflows/feedback_issue.yaml

@@ -6,11 +6,11 @@ jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/github-script@v4
+      - uses: actions/github-script@v6
         with:
           github-token: ${{secrets.GITHUB_TOKEN}}
           script: |
-            github.issues.createComment({
+            github.rest.issues.createComment({
               issue_number: context.issue.number,
               owner: context.repo.owner,
               repo: context.repo.repo,

.github/workflows/feedback_pull_request.yaml

@@ -6,11 +6,11 @@ jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/github-script@v4
+      - uses: actions/github-script@v6
         with:
           github-token: ${{secrets.GITHUB_TOKEN}}
           script: |
-            github.issues.createComment({
+            github.rest.issues.createComment({
               issue_number: context.issue.number,
               owner: context.repo.owner,
               repo: context.repo.repo,

.github/workflows/wasm.yml

@@ -1,26 +0,0 @@
-name: WASM
-
-on:
-  push:
-    branches:
-      - master
-  pull_request:
-
-jobs:
-  build:
-    name: Build
-    runs-on: ubuntu-latest
-    env:
-      GOFLAGS: -mod=readonly
-
-    steps:
-      - name: Set up Go
-        uses: actions/setup-go@v2
-        with:
-          go-version: '1.16'
-
-      - name: Checkout code
-        uses: actions/checkout@v2
-
-      - name: Ensure Viper compiles for WASM
-        run: GOOS=js GOARCH=wasm go build .

.golangci.yaml

@@ -3,7 +3,10 @@ run:
 
 linters-settings:
     gci:
-        local-prefixes: github.com/spf13/viper
+        sections:
+            - standard
+            - default
+            - prefix(github.com/spf13/viper)
     golint:
         min-confidence: 0
     goimports:
@@ -20,7 +23,6 @@ linters:
         - exhaustive
         - exportloopref
         - gci
-        - goconst
         - gofmt
         - gofumpt
         - goimports
@@ -62,6 +64,7 @@ linters:
         # - gochecknoglobals
         # - gochecknoinits
         # - gocognit
+        # - goconst
         # - gocritic
         # - gocyclo
         # - godot

Makefile

@@ -15,8 +15,8 @@ TEST_FORMAT = short-verbose
 endif
 
 # Dependency versions
-GOTESTSUM_VERSION = 1.6.4
-GOLANGCI_VERSION = 1.40.1
+GOTESTSUM_VERSION = 1.8.0
+GOLANGCI_VERSION = 1.50.1
 
 # Add the ability to override some variables
 # Use with care
@@ -48,7 +48,7 @@ bin/golangci-lint: bin/golangci-lint-${GOLANGCI_VERSION}
 	@ln -sf golangci-lint-${GOLANGCI_VERSION} bin/golangci-lint
 bin/golangci-lint-${GOLANGCI_VERSION}:
 	@mkdir -p bin
-	curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | bash -s -- -b ./bin/ v${GOLANGCI_VERSION}
+	curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | bash -s -- -b ./bin/ v${GOLANGCI_VERSION}
 	@mv bin/golangci-lint "$@"
 
 .PHONY: lint

README.md

@@ -8,10 +8,10 @@
 [![Mentioned in Awesome Go](https://awesome.re/mentioned-badge-flat.svg)](https://github.com/avelino/awesome-go#configuration)
 [![run on repl.it](https://repl.it/badge/github/sagikazarmark/Viper-example)](https://repl.it/@sagikazarmark/Viper-example#main.go)
 
-[![GitHub Workflow Status](https://img.shields.io/github/workflow/status/spf13/viper/CI?style=flat-square)](https://github.com/spf13/viper/actions?query=workflow%3ACI)
+[![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/spf13/viper/ci.yaml?branch=master&style=flat-square)](https://github.com/spf13/viper/actions?query=workflow%3ACI)
 [![Join the chat at https://gitter.im/spf13/viper](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/spf13/viper?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 [![Go Report Card](https://goreportcard.com/badge/github.com/spf13/viper?style=flat-square)](https://goreportcard.com/report/github.com/spf13/viper)
-![Go Version](https://img.shields.io/badge/go%20version-%3E=1.14-61CFDD.svg?style=flat-square)
+![Go Version](https://img.shields.io/badge/go%20version-%3E=1.16-61CFDD.svg?style=flat-square)
 [![PkgGoDev](https://pkg.go.dev/badge/mod/github.com/spf13/viper)](https://pkg.go.dev/mod/github.com/spf13/viper)
 
 **Go configuration with fangs!**
@@ -40,8 +40,8 @@ go get github.com/spf13/viper
 
 ## What is Viper?
 
-Viper is a complete configuration solution for Go applications including 12-Factor apps. It is designed
-to work within an application, and can handle all types of configuration needs
+Viper is a complete configuration solution for Go applications including [12-Factor apps](https://12factor.net/#the_twelve_factors).
+It is designed to work within an application, and can handle all types of configuration needs
 and formats. It supports:
 
 * setting defaults
@@ -119,7 +119,7 @@ viper.AddConfigPath("$HOME/.appname")  // call multiple times to add many search
 viper.AddConfigPath(".")               // optionally look for config in the working directory
 err := viper.ReadInConfig() // Find and read the config file
 if err != nil { // Handle errors reading the config file
-	panic(fmt.Errorf("Fatal error config file: %w \n", err))
+	panic(fmt.Errorf("fatal error config file: %w", err))
 }
 ```
 
@@ -127,11 +127,11 @@ You can handle the specific case where no config file is found like this:
 
 ```go
 if err := viper.ReadInConfig(); err != nil {
-    if _, ok := err.(viper.ConfigFileNotFoundError); ok {
-        // Config file not found; ignore error if desired
-    } else {
-        // Config file was found but another error was produced
-    }
+	if _, ok := err.(viper.ConfigFileNotFoundError); ok {
+		// Config file not found; ignore error if desired
+	} else {
+		// Config file was found but another error was produced
+	}
 }
 
 // Config file found and successfully parsed
@@ -175,10 +175,10 @@ Optionally you can provide a function for Viper to run each time a change occurs
 **Make sure you add all of the configPaths prior to calling `WatchConfig()`**
 
 ```go
-viper.WatchConfig()
 viper.OnConfigChange(func(e fsnotify.Event) {
 	fmt.Println("Config file changed:", e.Name)
 })
+viper.WatchConfig()
 ```
 
 ### Reading Config from io.Reader
@@ -354,7 +354,7 @@ func main() {
 
 	i := viper.GetInt("flagname") // retrieve value from viper
 
-	...
+	// ...
 }
 ```
 
@@ -447,6 +447,13 @@ viper.SetConfigType("json") // because there is no file extension in a stream of
 err := viper.ReadRemoteConfig()
 ```
 
+#### etcd3
+```go
+viper.AddRemoteProvider("etcd3", "http://127.0.0.1:4001","/config/hugo.json")
+viper.SetConfigType("json") // because there is no file extension in a stream of bytes, supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv"
+err := viper.ReadRemoteConfig()
+```
+
 #### Consul
 You need to set a key to Consul key/value storage with JSON value containing your desired config.
 For example, create a Consul key/value store key `MY_CONSUL_KEY` with value:
@@ -503,18 +510,18 @@ runtime_viper.Unmarshal(&runtime_conf)
 // open a goroutine to watch remote changes forever
 go func(){
 	for {
-	    time.Sleep(time.Second * 5) // delay after each request
+		time.Sleep(time.Second * 5) // delay after each request
 
-	    // currently, only tested with etcd support
-	    err := runtime_viper.WatchRemoteConfig()
-	    if err != nil {
-	        log.Errorf("unable to read remote config: %v", err)
-	        continue
-	    }
+		// currently, only tested with etcd support
+		err := runtime_viper.WatchRemoteConfig()
+		if err != nil {
+			log.Errorf("unable to read remote config: %v", err)
+			continue
+		}
 
-	    // unmarshal new config into our runtime config struct. you can also use channel
-	    // to implement a signal to notify the system of the changes
-	    runtime_viper.Unmarshal(&runtime_conf)
+		// unmarshal new config into our runtime config struct. you can also use channel
+		// to implement a signal to notify the system of the changes
+		runtime_viper.Unmarshal(&runtime_conf)
 	}
 }()
 ```
@@ -546,7 +553,7 @@ Example:
 ```go
 viper.GetString("logfile") // case-insensitive Setting & Getting
 if viper.GetBool("verbose") {
-    fmt.Println("verbose enabled")
+	fmt.Println("verbose enabled")
 }
 ```
 ### Accessing nested keys
@@ -594,7 +601,7 @@ configuration level.
 
 Viper can access array indices by using numbers in the path. For example:
 
-```json
+```jsonc
 {
     "host": {
         "address": "localhost",
@@ -622,7 +629,7 @@ GetInt("host.ports.1") // returns 6029
 Lastly, if there exists a key that matches the delimited key path, its value
 will be returned instead. E.g.
 
-```json
+```jsonc
 {
     "datastore.metric.host": "0.0.0.0",
     "host": {
@@ -669,7 +676,7 @@ So instead of doing that let's pass a Viper instance to the constructor that rep
 ```go
 cache1Config := viper.Sub("cache.cache1")
 if cache1Config == nil { // Sub returns nil if the key cannot be found
-    panic("cache configuration not found")
+	panic("cache configuration not found")
 }
 
 cache1 := NewCache(cache1Config)
@@ -681,10 +688,10 @@ Internally, the `NewCache` function can address `max-items` and `item-size` keys
 
 ```go
 func NewCache(v *Viper) *Cache {
-    return &Cache{
-        MaxItems: v.GetInt("max-items"),
-        ItemSize: v.GetInt("item-size"),
-    }
+	return &Cache{
+		MaxItems: v.GetInt("max-items"),
+		ItemSize: v.GetInt("item-size"),
+	}
 }
 ```
 
@@ -726,18 +733,18 @@ you have to change the delimiter:
 v := viper.NewWithOptions(viper.KeyDelimiter("::"))
 
 v.SetDefault("chart::values", map[string]interface{}{
-    "ingress": map[string]interface{}{
-        "annotations": map[string]interface{}{
-            "traefik.frontend.rule.type":                 "PathPrefix",
-            "traefik.ingress.kubernetes.io/ssl-redirect": "true",
-        },
-    },
+	"ingress": map[string]interface{}{
+		"annotations": map[string]interface{}{
+			"traefik.frontend.rule.type":                 "PathPrefix",
+			"traefik.ingress.kubernetes.io/ssl-redirect": "true",
+		},
+	},
 })
 
 type config struct {
 	Chart struct{
-        Values map[string]interface{}
-    }
+		Values map[string]interface{}
+	}
 }
 
 var C config
@@ -794,17 +801,17 @@ You can use your favorite format's marshaller with the config returned by `AllSe
 
 ```go
 import (
-    yaml "gopkg.in/yaml.v2"
-    // ...
+	yaml "gopkg.in/yaml.v2"
+	// ...
 )
 
 func yamlStringSettings() string {
-    c := viper.AllSettings()
-    bs, err := yaml.Marshal(c)
-    if err != nil {
-        log.Fatalf("unable to marshal config to YAML: %v", err)
-    }
-    return string(bs)
+	c := viper.AllSettings()
+	bs, err := yaml.Marshal(c)
+	if err != nil {
+		log.Fatalf("unable to marshal config to YAML: %v", err)
+	}
+	return string(bs)
 }
 ```
 

TROUBLESHOOTING.md

@@ -21,3 +21,12 @@ The solution is easy: switch to using Go Modules.
 Please refer to the [wiki](https://github.com/golang/go/wiki/Modules) on how to do that.
 
 **tl;dr* `export GO111MODULE=on`
+
+## Unquoted 'y' and 'n' characters get replaced with _true_ and _false_ when reading a YAML file
+
+This is a YAML 1.1 feature according to [go-yaml/yaml#740](https://github.com/go-yaml/yaml/issues/740).
+
+Potential solutions are:
+
+1. Quoting values resolved as boolean
+1. Upgrading to YAML v3 (for the time being this is possible by passing the `viper_yaml3` tag to your build)

experimental_logger.go

@@ -0,0 +1,11 @@
+//go:build viper_logger
+// +build viper_logger
+
+package viper
+
+// WithLogger sets a custom logger.
+func WithLogger(l Logger) Option {
+	return optionFunc(func(v *Viper) {
+		v.logger = l
+	})
+}

fs.go

@@ -0,0 +1,65 @@
+//go:build go1.16 && finder
+// +build go1.16,finder
+
+package viper
+
+import (
+	"errors"
+	"io/fs"
+	"path"
+)
+
+type finder struct {
+	paths      []string
+	fileNames  []string
+	extensions []string
+
+	withoutExtension bool
+}
+
+func (f finder) Find(fsys fs.FS) (string, error) {
+	for _, searchPath := range f.paths {
+		for _, fileName := range f.fileNames {
+			for _, extension := range f.extensions {
+				filePath := path.Join(searchPath, fileName+"."+extension)
+
+				ok, err := fileExists(fsys, filePath)
+				if err != nil {
+					return "", err
+				}
+
+				if ok {
+					return filePath, nil
+				}
+			}
+
+			if f.withoutExtension {
+				filePath := path.Join(searchPath, fileName)
+
+				ok, err := fileExists(fsys, filePath)
+				if err != nil {
+					return "", err
+				}
+
+				if ok {
+					return filePath, nil
+				}
+			}
+		}
+	}
+
+	return "", nil
+}
+
+func fileExists(fsys fs.FS, filePath string) (bool, error) {
+	fileInfo, err := fs.Stat(fsys, filePath)
+	if err == nil {
+		return !fileInfo.IsDir(), nil
+	}
+
+	if errors.Is(err, fs.ErrNotExist) {
+		return false, nil
+	}
+
+	return false, err
+}

fs_test.go

@@ -0,0 +1,100 @@
+//go:build go1.16 && finder
+// +build go1.16,finder
+
+package viper
+
+import (
+	"io/fs"
+	"testing"
+	"testing/fstest"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFinder(t *testing.T) {
+	t.Parallel()
+
+	fsys := fstest.MapFS{
+		"home/user/.config":            &fstest.MapFile{},
+		"home/user/config.json":        &fstest.MapFile{},
+		"home/user/config.yaml":        &fstest.MapFile{},
+		"home/user/data.json":          &fstest.MapFile{},
+		"etc/config/.config":           &fstest.MapFile{},
+		"etc/config/a_random_file.txt": &fstest.MapFile{},
+		"etc/config/config.json":       &fstest.MapFile{},
+		"etc/config/config.yaml":       &fstest.MapFile{},
+		"etc/config/config.xml":        &fstest.MapFile{},
+	}
+
+	testCases := []struct {
+		name   string
+		fsys   func() fs.FS
+		finder finder
+		result string
+	}{
+		{
+			name: "find file",
+			fsys: func() fs.FS { return fsys },
+			finder: finder{
+				paths:      []string{"etc/config"},
+				fileNames:  []string{"config"},
+				extensions: []string{"json"},
+			},
+			result: "etc/config/config.json",
+		},
+		{
+			name: "file not found",
+			fsys: func() fs.FS { return fsys },
+			finder: finder{
+				paths:      []string{"var/config"},
+				fileNames:  []string{"config"},
+				extensions: []string{"json"},
+			},
+			result: "",
+		},
+		{
+			name:   "empty search params",
+			fsys:   func() fs.FS { return fsys },
+			finder: finder{},
+			result: "",
+		},
+		{
+			name: "precedence",
+			fsys: func() fs.FS { return fsys },
+			finder: finder{
+				paths:      []string{"var/config", "home/user", "etc/config"},
+				fileNames:  []string{"aconfig", "config"},
+				extensions: []string{"zml", "xml", "json"},
+			},
+			result: "home/user/config.json",
+		},
+		{
+			name: "without extension",
+			fsys: func() fs.FS { return fsys },
+			finder: finder{
+				paths:      []string{"var/config", "home/user", "etc/config"},
+				fileNames:  []string{".config"},
+				extensions: []string{"zml", "xml", "json"},
+
+				withoutExtension: true,
+			},
+			result: "home/user/.config",
+		},
+	}
+
+	for _, testCase := range testCases {
+		testCase := testCase
+
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			fsys := testCase.fsys()
+
+			result, err := testCase.finder.Find(fsys)
+			require.NoError(t, err)
+
+			assert.Equal(t, testCase.result, result)
+		})
+	}
+}

go.mod

@@ -1,21 +1,75 @@
 module github.com/spf13/viper
 
-go 1.12
+go 1.17
 
 require (
-	github.com/bketelsen/crypt v0.0.4
-	github.com/fsnotify/fsnotify v1.4.9
+	github.com/fsnotify/fsnotify v1.6.0
 	github.com/hashicorp/hcl v1.0.0
-	github.com/magiconair/properties v1.8.5
-	github.com/mitchellh/mapstructure v1.4.1
-	github.com/pelletier/go-toml v1.9.3
-	github.com/smartystreets/goconvey v1.6.4 // indirect
-	github.com/spf13/afero v1.6.0
-	github.com/spf13/cast v1.3.1
+	github.com/magiconair/properties v1.8.7
+	github.com/mitchellh/mapstructure v1.5.0
+	github.com/pelletier/go-toml/v2 v2.0.6
+	github.com/sagikazarmark/crypt v0.9.0
+	github.com/spf13/afero v1.9.3
+	github.com/spf13/cast v1.5.0
 	github.com/spf13/jwalterweatherman v1.1.0
 	github.com/spf13/pflag v1.0.5
-	github.com/stretchr/testify v1.7.0
-	github.com/subosito/gotenv v1.2.0
-	gopkg.in/ini.v1 v1.62.0
-	gopkg.in/yaml.v2 v2.4.0
+	github.com/stretchr/testify v1.8.1
+	github.com/subosito/gotenv v1.4.2
+	gopkg.in/ini.v1 v1.67.0
+	gopkg.in/yaml.v3 v3.0.1
+)
+
+require (
+	cloud.google.com/go v0.105.0 // indirect
+	cloud.google.com/go/compute v1.14.0 // indirect
+	cloud.google.com/go/compute/metadata v0.2.3 // indirect
+	cloud.google.com/go/firestore v1.9.0 // indirect
+	cloud.google.com/go/longrunning v0.3.0 // indirect
+	github.com/armon/go-metrics v0.4.0 // indirect
+	github.com/coreos/go-semver v0.3.0 // indirect
+	github.com/coreos/go-systemd/v22 v22.3.2 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/fatih/color v1.13.0 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
+	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/google/go-cmp v0.5.9 // indirect
+	github.com/googleapis/enterprise-certificate-proxy v0.2.1 // indirect
+	github.com/googleapis/gax-go/v2 v2.7.0 // indirect
+	github.com/hashicorp/consul/api v1.18.0 // indirect
+	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect
+	github.com/hashicorp/go-hclog v1.2.0 // indirect
+	github.com/hashicorp/go-immutable-radix v1.3.1 // indirect
+	github.com/hashicorp/go-rootcerts v1.0.2 // indirect
+	github.com/hashicorp/golang-lru v0.5.4 // indirect
+	github.com/hashicorp/serf v0.10.1 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/mattn/go-colorable v0.1.12 // indirect
+	github.com/mattn/go-isatty v0.0.14 // indirect
+	github.com/mitchellh/go-homedir v1.1.0 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.etcd.io/etcd/api/v3 v3.5.6 // indirect
+	go.etcd.io/etcd/client/pkg/v3 v3.5.6 // indirect
+	go.etcd.io/etcd/client/v2 v2.305.6 // indirect
+	go.etcd.io/etcd/client/v3 v3.5.6 // indirect
+	go.opencensus.io v0.24.0 // indirect
+	go.uber.org/atomic v1.9.0 // indirect
+	go.uber.org/multierr v1.8.0 // indirect
+	go.uber.org/zap v1.21.0 // indirect
+	golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e // indirect
+	golang.org/x/net v0.4.0 // indirect
+	golang.org/x/oauth2 v0.0.0-20221014153046-6fdb5e3db783 // indirect
+	golang.org/x/sync v0.1.0 // indirect
+	golang.org/x/sys v0.3.0 // indirect
+	golang.org/x/text v0.5.0 // indirect
+	golang.org/x/time v0.1.0 // indirect
+	golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect
+	google.golang.org/api v0.107.0 // indirect
+	google.golang.org/appengine v1.6.7 // indirect
+	google.golang.org/genproto v0.0.0-20221227171554-f9683d7f8bef // indirect
+	google.golang.org/grpc v1.52.0 // indirect
+	google.golang.org/protobuf v1.28.1 // indirect
 )

internal/encoding/decoder.go

@@ -4,10 +4,10 @@ import (
 	"sync"
 )
 
-// Decoder decodes the contents of b into a v representation.
+// Decoder decodes the contents of b into v.
 // It's primarily used for decoding contents of a file into a map[string]interface{}.
 type Decoder interface {
-	Decode(b []byte, v interface{}) error
+	Decode(b []byte, v map[string]interface{}) error
 }
 
 const (
@@ -48,7 +48,7 @@ func (e *DecoderRegistry) RegisterDecoder(format string, enc Decoder) error {
 }
 
 // Decode calls the underlying Decoder based on the format.
-func (e *DecoderRegistry) Decode(format string, b []byte, v interface{}) error {
+func (e *DecoderRegistry) Decode(format string, b []byte, v map[string]interface{}) error {
 	e.mu.RLock()
 	decoder, ok := e.decoders[format]
 	e.mu.RUnlock()

internal/encoding/decoder_test.go

@@ -1,16 +1,18 @@
 package encoding
 
 import (
+	"reflect"
 	"testing"
 )
 
 type decoder struct {
-	v interface{}
+	v map[string]interface{}
 }
 
-func (d decoder) Decode(_ []byte, v interface{}) error {
-	rv := v.(*string)
-	*rv = d.v.(string)
+func (d decoder) Decode(_ []byte, v map[string]interface{}) error {
+	for key, value := range d.v {
+		v[key] = value
+	}
 
 	return nil
 }
@@ -44,7 +46,9 @@ func TestDecoderRegistry_Decode(t *testing.T) {
 	t.Run("OK", func(t *testing.T) {
 		registry := NewDecoderRegistry()
 		decoder := decoder{
-			v: "decoded value",
+			v: map[string]interface{}{
+				"key": "value",
+			},
 		}
 
 		err := registry.RegisterDecoder("myformat", decoder)
@@ -52,24 +56,24 @@ func TestDecoderRegistry_Decode(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		var v string
+		v := map[string]interface{}{}
 
-		err = registry.Decode("myformat", []byte("some value"), &v)
+		err = registry.Decode("myformat", []byte("key: value"), v)
 		if err != nil {
 			t.Fatal(err)
 		}
 
-		if v != "decoded value" {
-			t.Fatalf("expected 'decoded value', got: %#v", v)
+		if !reflect.DeepEqual(decoder.v, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %+v\nexpected: %+v", v, decoder.v)
 		}
 	})
 
 	t.Run("DecoderNotFound", func(t *testing.T) {
 		registry := NewDecoderRegistry()
 
-		var v string
+		v := map[string]interface{}{}
 
-		err := registry.Decode("myformat", []byte("some value"), &v)
+		err := registry.Decode("myformat", nil, v)
 		if err != ErrDecoderNotFound {
 			t.Fatalf("expected ErrDecoderNotFound, got: %v", err)
 		}

internal/encoding/dotenv/codec.go

@@ -0,0 +1,61 @@
+package dotenv
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/subosito/gotenv"
+)
+
+const keyDelimiter = "_"
+
+// Codec implements the encoding.Encoder and encoding.Decoder interfaces for encoding data containing environment variables
+// (commonly called as dotenv format).
+type Codec struct{}
+
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
+	flattened := map[string]interface{}{}
+
+	flattened = flattenAndMergeMap(flattened, v, "", keyDelimiter)
+
+	keys := make([]string, 0, len(flattened))
+
+	for key := range flattened {
+		keys = append(keys, key)
+	}
+
+	sort.Strings(keys)
+
+	var buf bytes.Buffer
+
+	for _, key := range keys {
+		_, err := buf.WriteString(fmt.Sprintf("%v=%v\n", strings.ToUpper(key), flattened[key]))
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (Codec) Decode(b []byte, v map[string]interface{}) error {
+	var buf bytes.Buffer
+
+	_, err := buf.Write(b)
+	if err != nil {
+		return err
+	}
+
+	env, err := gotenv.StrictParse(&buf)
+	if err != nil {
+		return err
+	}
+
+	for key, value := range env {
+		v[key] = value
+	}
+
+	return nil
+}

internal/encoding/dotenv/codec_test.go

@@ -0,0 +1,63 @@
+package dotenv
+
+import (
+	"reflect"
+	"testing"
+)
+
+// original form of the data
+const original = `# key-value pair
+KEY=value
+`
+
+// encoded form of the data
+const encoded = `KEY=value
+`
+
+// Viper's internal representation
+var data = map[string]interface{}{
+	"KEY": "value",
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if encoded != string(b) {
+		t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+	}
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(original), v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(data, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", v, data)
+		}
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		if err == nil {
+			t.Fatal("expected decoding to fail")
+		}
+
+		t.Logf("decoding failed as expected: %s", err)
+	})
+}

internal/encoding/dotenv/map_utils.go

@@ -0,0 +1,41 @@
+package dotenv
+
+import (
+	"strings"
+
+	"github.com/spf13/cast"
+)
+
+// flattenAndMergeMap recursively flattens the given map into a new map
+// Code is based on the function with the same name in tha main package.
+// TODO: move it to a common place
+func flattenAndMergeMap(shadow map[string]interface{}, m map[string]interface{}, prefix string, delimiter string) map[string]interface{} {
+	if shadow != nil && prefix != "" && shadow[prefix] != nil {
+		// prefix is shadowed => nothing more to flatten
+		return shadow
+	}
+	if shadow == nil {
+		shadow = make(map[string]interface{})
+	}
+
+	var m2 map[string]interface{}
+	if prefix != "" {
+		prefix += delimiter
+	}
+	for k, val := range m {
+		fullKey := prefix + k
+		switch val.(type) {
+		case map[string]interface{}:
+			m2 = val.(map[string]interface{})
+		case map[interface{}]interface{}:
+			m2 = cast.ToStringMap(val)
+		default:
+			// immediate value
+			shadow[strings.ToLower(fullKey)] = val
+			continue
+		}
+		// recursively merge to shadow map
+		shadow = flattenAndMergeMap(shadow, m2, fullKey, delimiter)
+	}
+	return shadow
+}

internal/encoding/encoder.go

@@ -7,7 +7,7 @@ import (
 // Encoder encodes the contents of v into a byte representation.
 // It's primarily used for encoding a map[string]interface{} into a file format.
 type Encoder interface {
-	Encode(v interface{}) ([]byte, error)
+	Encode(v map[string]interface{}) ([]byte, error)
 }
 
 const (
@@ -47,7 +47,7 @@ func (e *EncoderRegistry) RegisterEncoder(format string, enc Encoder) error {
 	return nil
 }
 
-func (e *EncoderRegistry) Encode(format string, v interface{}) ([]byte, error) {
+func (e *EncoderRegistry) Encode(format string, v map[string]interface{}) ([]byte, error) {
 	e.mu.RLock()
 	encoder, ok := e.encoders[format]
 	e.mu.RUnlock()

internal/encoding/encoder_test.go

@@ -8,7 +8,7 @@ type encoder struct {
 	b []byte
 }
 
-func (e encoder) Encode(_ interface{}) ([]byte, error) {
+func (e encoder) Encode(_ map[string]interface{}) ([]byte, error) {
 	return e.b, nil
 }
 
@@ -41,7 +41,7 @@ func TestEncoderRegistry_Decode(t *testing.T) {
 	t.Run("OK", func(t *testing.T) {
 		registry := NewEncoderRegistry()
 		encoder := encoder{
-			b: []byte("encoded value"),
+			b: []byte("key: value"),
 		}
 
 		err := registry.RegisterEncoder("myformat", encoder)
@@ -49,20 +49,20 @@ func TestEncoderRegistry_Decode(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		b, err := registry.Encode("myformat", "some value")
+		b, err := registry.Encode("myformat", map[string]interface{}{"key": "value"})
 		if err != nil {
 			t.Fatal(err)
 		}
 
-		if string(b) != "encoded value" {
-			t.Fatalf("expected 'encoded value', got: %#v", string(b))
+		if string(b) != "key: value" {
+			t.Fatalf("expected 'key: value', got: %#v", string(b))
 		}
 	})
 
 	t.Run("EncoderNotFound", func(t *testing.T) {
 		registry := NewEncoderRegistry()
 
-		_, err := registry.Encode("myformat", "some value")
+		_, err := registry.Encode("myformat", map[string]interface{}{"key": "value"})
 		if err != ErrEncoderNotFound {
 			t.Fatalf("expected ErrEncoderNotFound, got: %v", err)
 		}

internal/encoding/hcl/codec.go

@@ -12,7 +12,7 @@ import (
 // TODO: add printer config to the codec?
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
 	b, err := json.Marshal(v)
 	if err != nil {
 		return nil, err
@@ -35,6 +35,6 @@ func (Codec) Encode(v interface{}) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-func (Codec) Decode(b []byte, v interface{}) error {
-	return hcl.Unmarshal(b, v)
+func (Codec) Decode(b []byte, v map[string]interface{}) error {
+	return hcl.Unmarshal(b, &v)
 }

internal/encoding/hcl/codec_test.go

@@ -0,0 +1,140 @@
+package hcl
+
+import (
+	"reflect"
+	"testing"
+)
+
+// original form of the data
+const original = `# key-value pair
+"key" = "value"
+
+// list
+"list" = ["item1", "item2", "item3"]
+
+/* map */
+"map" = {
+  "key" = "value"
+}
+
+/*
+nested map
+*/
+"nested_map" "map" {
+  "key" = "value"
+
+  "list" = ["item1", "item2", "item3"]
+}`
+
+// encoded form of the data
+const encoded = `"key" = "value"
+
+"list" = ["item1", "item2", "item3"]
+
+"map" = {
+  "key" = "value"
+}
+
+"nested_map" "map" {
+  "key" = "value"
+
+  "list" = ["item1", "item2", "item3"]
+}`
+
+// decoded form of the data
+//
+// in case of HCL it's slightly different from Viper's internal representation
+// (eg. map is decoded into a list of maps)
+var decoded = map[string]interface{}{
+	"key": "value",
+	"list": []interface{}{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": []map[string]interface{}{
+		{
+			"key": "value",
+		},
+	},
+	"nested_map": []map[string]interface{}{
+		{
+			"map": []map[string]interface{}{
+				{
+					"key": "value",
+					"list": []interface{}{
+						"item1",
+						"item2",
+						"item3",
+					},
+				},
+			},
+		},
+	},
+}
+
+// Viper's internal representation
+var data = map[string]interface{}{
+	"key": "value",
+	"list": []interface{}{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+	"nested_map": map[string]interface{}{
+		"map": map[string]interface{}{
+			"key": "value",
+			"list": []interface{}{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if encoded != string(b) {
+		t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+	}
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(original), v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(decoded, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", v, decoded)
+		}
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		if err == nil {
+			t.Fatal("expected decoding to fail")
+		}
+
+		t.Logf("decoding failed as expected: %s", err)
+	})
+}

internal/encoding/ini/codec.go

@@ -0,0 +1,99 @@
+package ini
+
+import (
+	"bytes"
+	"sort"
+	"strings"
+
+	"github.com/spf13/cast"
+	"gopkg.in/ini.v1"
+)
+
+// LoadOptions contains all customized options used for load data source(s).
+// This type is added here for convenience: this way consumers can import a single package called "ini".
+type LoadOptions = ini.LoadOptions
+
+// Codec implements the encoding.Encoder and encoding.Decoder interfaces for INI encoding.
+type Codec struct {
+	KeyDelimiter string
+	LoadOptions  LoadOptions
+}
+
+func (c Codec) Encode(v map[string]interface{}) ([]byte, error) {
+	cfg := ini.Empty()
+	ini.PrettyFormat = false
+
+	flattened := map[string]interface{}{}
+
+	flattened = flattenAndMergeMap(flattened, v, "", c.keyDelimiter())
+
+	keys := make([]string, 0, len(flattened))
+
+	for key := range flattened {
+		keys = append(keys, key)
+	}
+
+	sort.Strings(keys)
+
+	for _, key := range keys {
+		sectionName, keyName := "", key
+
+		lastSep := strings.LastIndex(key, ".")
+		if lastSep != -1 {
+			sectionName = key[:(lastSep)]
+			keyName = key[(lastSep + 1):]
+		}
+
+		// TODO: is this a good idea?
+		if sectionName == "default" {
+			sectionName = ""
+		}
+
+		cfg.Section(sectionName).Key(keyName).SetValue(cast.ToString(flattened[key]))
+	}
+
+	var buf bytes.Buffer
+
+	_, err := cfg.WriteTo(&buf)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (c Codec) Decode(b []byte, v map[string]interface{}) error {
+	cfg := ini.Empty(c.LoadOptions)
+
+	err := cfg.Append(b)
+	if err != nil {
+		return err
+	}
+
+	sections := cfg.Sections()
+
+	for i := 0; i < len(sections); i++ {
+		section := sections[i]
+		keys := section.Keys()
+
+		for j := 0; j < len(keys); j++ {
+			key := keys[j]
+			value := cfg.Section(section.Name()).Key(key.Name()).String()
+
+			deepestMap := deepSearch(v, strings.Split(section.Name(), c.keyDelimiter()))
+
+			// set innermost value
+			deepestMap[key.Name()] = value
+		}
+	}
+
+	return nil
+}
+
+func (c Codec) keyDelimiter() string {
+	if c.KeyDelimiter == "" {
+		return "."
+	}
+
+	return c.KeyDelimiter
+}

internal/encoding/ini/codec_test.go

@@ -0,0 +1,111 @@
+package ini
+
+import (
+	"reflect"
+	"testing"
+)
+
+// original form of the data
+const original = `; key-value pair
+key=value ; key-value pair
+
+# map
+[map] # map
+key=%(key)s
+
+`
+
+// encoded form of the data
+const encoded = `key=value
+
+[map]
+key=value
+`
+
+// decoded form of the data
+//
+// in case of INI it's slightly different from Viper's internal representation
+// (eg. top level keys land in a section called default)
+var decoded = map[string]interface{}{
+	"DEFAULT": map[string]interface{}{
+		"key": "value",
+	},
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+}
+
+// Viper's internal representation
+var data = map[string]interface{}{
+	"key": "value",
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		b, err := codec.Encode(data)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if encoded != string(b) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+		}
+	})
+
+	t.Run("Default", func(t *testing.T) {
+		codec := Codec{}
+
+		data := map[string]interface{}{
+			"default": map[string]interface{}{
+				"key": "value",
+			},
+			"map": map[string]interface{}{
+				"key": "value",
+			},
+		}
+
+		b, err := codec.Encode(data)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if encoded != string(b) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+		}
+	})
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(original), v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(decoded, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", v, decoded)
+		}
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		if err == nil {
+			t.Fatal("expected decoding to fail")
+		}
+
+		t.Logf("decoding failed as expected: %s", err)
+	})
+}

internal/encoding/ini/map_utils.go

@@ -0,0 +1,74 @@
+package ini
+
+import (
+	"strings"
+
+	"github.com/spf13/cast"
+)
+
+// THIS CODE IS COPIED HERE: IT SHOULD NOT BE MODIFIED
+// AT SOME POINT IT WILL BE MOVED TO A COMMON PLACE
+// deepSearch scans deep maps, following the key indexes listed in the
+// sequence "path".
+// The last value is expected to be another map, and is returned.
+//
+// In case intermediate keys do not exist, or map to a non-map value,
+// a new map is created and inserted, and the search continues from there:
+// the initial map "m" may be modified!
+func deepSearch(m map[string]interface{}, path []string) map[string]interface{} {
+	for _, k := range path {
+		m2, ok := m[k]
+		if !ok {
+			// intermediate key does not exist
+			// => create it and continue from there
+			m3 := make(map[string]interface{})
+			m[k] = m3
+			m = m3
+			continue
+		}
+		m3, ok := m2.(map[string]interface{})
+		if !ok {
+			// intermediate key is a value
+			// => replace with a new map
+			m3 = make(map[string]interface{})
+			m[k] = m3
+		}
+		// continue search from here
+		m = m3
+	}
+	return m
+}
+
+// flattenAndMergeMap recursively flattens the given map into a new map
+// Code is based on the function with the same name in tha main package.
+// TODO: move it to a common place
+func flattenAndMergeMap(shadow map[string]interface{}, m map[string]interface{}, prefix string, delimiter string) map[string]interface{} {
+	if shadow != nil && prefix != "" && shadow[prefix] != nil {
+		// prefix is shadowed => nothing more to flatten
+		return shadow
+	}
+	if shadow == nil {
+		shadow = make(map[string]interface{})
+	}
+
+	var m2 map[string]interface{}
+	if prefix != "" {
+		prefix += delimiter
+	}
+	for k, val := range m {
+		fullKey := prefix + k
+		switch val.(type) {
+		case map[string]interface{}:
+			m2 = val.(map[string]interface{})
+		case map[interface{}]interface{}:
+			m2 = cast.ToStringMap(val)
+		default:
+			// immediate value
+			shadow[strings.ToLower(fullKey)] = val
+			continue
+		}
+		// recursively merge to shadow map
+		shadow = flattenAndMergeMap(shadow, m2, fullKey, delimiter)
+	}
+	return shadow
+}

internal/encoding/javaproperties/codec.go

@@ -0,0 +1,86 @@
+package javaproperties
+
+import (
+	"bytes"
+	"sort"
+	"strings"
+
+	"github.com/magiconair/properties"
+	"github.com/spf13/cast"
+)
+
+// Codec implements the encoding.Encoder and encoding.Decoder interfaces for Java properties encoding.
+type Codec struct {
+	KeyDelimiter string
+
+	// Store read properties on the object so that we can write back in order with comments.
+	// This will only be used if the configuration read is a properties file.
+	// TODO: drop this feature in v2
+	// TODO: make use of the global properties object optional
+	Properties *properties.Properties
+}
+
+func (c *Codec) Encode(v map[string]interface{}) ([]byte, error) {
+	if c.Properties == nil {
+		c.Properties = properties.NewProperties()
+	}
+
+	flattened := map[string]interface{}{}
+
+	flattened = flattenAndMergeMap(flattened, v, "", c.keyDelimiter())
+
+	keys := make([]string, 0, len(flattened))
+
+	for key := range flattened {
+		keys = append(keys, key)
+	}
+
+	sort.Strings(keys)
+
+	for _, key := range keys {
+		_, _, err := c.Properties.Set(key, cast.ToString(flattened[key]))
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	var buf bytes.Buffer
+
+	_, err := c.Properties.WriteComment(&buf, "#", properties.UTF8)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (c *Codec) Decode(b []byte, v map[string]interface{}) error {
+	var err error
+	c.Properties, err = properties.Load(b, properties.UTF8)
+	if err != nil {
+		return err
+	}
+
+	for _, key := range c.Properties.Keys() {
+		// ignore existence check: we know it's there
+		value, _ := c.Properties.Get(key)
+
+		// recursively build nested maps
+		path := strings.Split(key, c.keyDelimiter())
+		lastKey := strings.ToLower(path[len(path)-1])
+		deepestMap := deepSearch(v, path[0:len(path)-1])
+
+		// set innermost value
+		deepestMap[lastKey] = value
+	}
+
+	return nil
+}
+
+func (c Codec) keyDelimiter() string {
+	if c.KeyDelimiter == "" {
+		return "."
+	}
+
+	return c.KeyDelimiter
+}

internal/encoding/javaproperties/codec_test.go

@@ -0,0 +1,89 @@
+package javaproperties
+
+import (
+	"reflect"
+	"testing"
+)
+
+// original form of the data
+const original = `#key-value pair
+key = value
+map.key = value
+`
+
+// encoded form of the data
+const encoded = `key = value
+map.key = value
+`
+
+// Viper's internal representation
+var data = map[string]interface{}{
+	"key": "value",
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if encoded != string(b) {
+		t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+	}
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(original), v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(data, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", v, data)
+		}
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		t.Skip("TODO: needs invalid data example")
+
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		codec.Decode([]byte(``), v)
+
+		if len(v) > 0 {
+			t.Fatalf("expected map to be empty when data is invalid\nactual: %#v", v)
+		}
+	})
+}
+
+func TestCodec_DecodeEncode(t *testing.T) {
+	codec := Codec{}
+
+	v := map[string]interface{}{}
+
+	err := codec.Decode([]byte(original), v)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := codec.Encode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if original != string(b) {
+		t.Fatalf("encoded value does not match the original\nactual:   %#v\nexpected: %#v", string(b), original)
+	}
+}

internal/encoding/javaproperties/map_utils.go

@@ -0,0 +1,74 @@
+package javaproperties
+
+import (
+	"strings"
+
+	"github.com/spf13/cast"
+)
+
+// THIS CODE IS COPIED HERE: IT SHOULD NOT BE MODIFIED
+// AT SOME POINT IT WILL BE MOVED TO A COMMON PLACE
+// deepSearch scans deep maps, following the key indexes listed in the
+// sequence "path".
+// The last value is expected to be another map, and is returned.
+//
+// In case intermediate keys do not exist, or map to a non-map value,
+// a new map is created and inserted, and the search continues from there:
+// the initial map "m" may be modified!
+func deepSearch(m map[string]interface{}, path []string) map[string]interface{} {
+	for _, k := range path {
+		m2, ok := m[k]
+		if !ok {
+			// intermediate key does not exist
+			// => create it and continue from there
+			m3 := make(map[string]interface{})
+			m[k] = m3
+			m = m3
+			continue
+		}
+		m3, ok := m2.(map[string]interface{})
+		if !ok {
+			// intermediate key is a value
+			// => replace with a new map
+			m3 = make(map[string]interface{})
+			m[k] = m3
+		}
+		// continue search from here
+		m = m3
+	}
+	return m
+}
+
+// flattenAndMergeMap recursively flattens the given map into a new map
+// Code is based on the function with the same name in tha main package.
+// TODO: move it to a common place
+func flattenAndMergeMap(shadow map[string]interface{}, m map[string]interface{}, prefix string, delimiter string) map[string]interface{} {
+	if shadow != nil && prefix != "" && shadow[prefix] != nil {
+		// prefix is shadowed => nothing more to flatten
+		return shadow
+	}
+	if shadow == nil {
+		shadow = make(map[string]interface{})
+	}
+
+	var m2 map[string]interface{}
+	if prefix != "" {
+		prefix += delimiter
+	}
+	for k, val := range m {
+		fullKey := prefix + k
+		switch val.(type) {
+		case map[string]interface{}:
+			m2 = val.(map[string]interface{})
+		case map[interface{}]interface{}:
+			m2 = cast.ToStringMap(val)
+		default:
+			// immediate value
+			shadow[strings.ToLower(fullKey)] = val
+			continue
+		}
+		// recursively merge to shadow map
+		shadow = flattenAndMergeMap(shadow, m2, fullKey, delimiter)
+	}
+	return shadow
+}

internal/encoding/json/codec.go

@@ -7,11 +7,11 @@ import (
 // Codec implements the encoding.Encoder and encoding.Decoder interfaces for JSON encoding.
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
 	// TODO: expose prefix and indent in the Codec as setting?
 	return json.MarshalIndent(v, "", "  ")
 }
 
-func (Codec) Decode(b []byte, v interface{}) error {
-	return json.Unmarshal(b, v)
+func (Codec) Decode(b []byte, v map[string]interface{}) error {
+	return json.Unmarshal(b, &v)
 }

internal/encoding/json/codec_test.go

@@ -0,0 +1,95 @@
+package json
+
+import (
+	"reflect"
+	"testing"
+)
+
+// encoded form of the data
+const encoded = `{
+  "key": "value",
+  "list": [
+    "item1",
+    "item2",
+    "item3"
+  ],
+  "map": {
+    "key": "value"
+  },
+  "nested_map": {
+    "map": {
+      "key": "value",
+      "list": [
+        "item1",
+        "item2",
+        "item3"
+      ]
+    }
+  }
+}`
+
+// Viper's internal representation
+var data = map[string]interface{}{
+	"key": "value",
+	"list": []interface{}{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+	"nested_map": map[string]interface{}{
+		"map": map[string]interface{}{
+			"key": "value",
+			"list": []interface{}{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if encoded != string(b) {
+		t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+	}
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(encoded), v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(data, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", v, data)
+		}
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		if err == nil {
+			t.Fatal("expected decoding to fail")
+		}
+
+		t.Logf("decoding failed as expected: %s", err)
+	})
+}

internal/encoding/toml/codec.go

@@ -1,45 +1,16 @@
 package toml
 
 import (
-	"github.com/pelletier/go-toml"
+	"github.com/pelletier/go-toml/v2"
 )
 
 // Codec implements the encoding.Encoder and encoding.Decoder interfaces for TOML encoding.
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
-	if m, ok := v.(map[string]interface{}); ok {
-		t, err := toml.TreeFromMap(m)
-		if err != nil {
-			return nil, err
-		}
-
-		s, err := t.ToTomlString()
-		if err != nil {
-			return nil, err
-		}
-
-		return []byte(s), nil
-	}
-
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
 	return toml.Marshal(v)
 }
 
-func (Codec) Decode(b []byte, v interface{}) error {
-	tree, err := toml.LoadBytes(b)
-	if err != nil {
-		return err
-	}
-
-	if m, ok := v.(*map[string]interface{}); ok {
-		vmap := *m
-		tmap := tree.ToMap()
-		for k, v := range tmap {
-			vmap[k] = v
-		}
-
-		return nil
-	}
-
-	return tree.Unmarshal(v)
+func (Codec) Decode(b []byte, v map[string]interface{}) error {
+	return toml.Unmarshal(b, &v)
 }

internal/encoding/toml/codec_test.go

@@ -0,0 +1,105 @@
+package toml
+
+import (
+	"reflect"
+	"testing"
+)
+
+// original form of the data
+const original = `# key-value pair
+key = "value"
+list = ["item1", "item2", "item3"]
+
+[map]
+key = "value"
+
+# nested
+# map
+[nested_map]
+[nested_map.map]
+key = "value"
+list = [
+  "item1",
+  "item2",
+  "item3",
+]
+`
+
+// encoded form of the data
+const encoded = `key = 'value'
+list = ['item1', 'item2', 'item3']
+
+[map]
+key = 'value'
+
+[nested_map]
+[nested_map.map]
+key = 'value'
+list = ['item1', 'item2', 'item3']
+`
+
+// Viper's internal representation
+var data = map[string]interface{}{
+	"key": "value",
+	"list": []interface{}{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+	"nested_map": map[string]interface{}{
+		"map": map[string]interface{}{
+			"key": "value",
+			"list": []interface{}{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if encoded != string(b) {
+		t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+	}
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(original), v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(data, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", v, data)
+		}
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		if err == nil {
+			t.Fatal("expected decoding to fail")
+		}
+
+		t.Logf("decoding failed as expected: %s", err)
+	})
+}

internal/encoding/yaml/codec.go

@@ -1,14 +1,14 @@
 package yaml
 
-import "gopkg.in/yaml.v2"
+import "gopkg.in/yaml.v3"
 
 // Codec implements the encoding.Encoder and encoding.Decoder interfaces for YAML encoding.
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
 	return yaml.Marshal(v)
 }
 
-func (Codec) Decode(b []byte, v interface{}) error {
-	return yaml.Unmarshal(b, v)
+func (Codec) Decode(b []byte, v map[string]interface{}) error {
+	return yaml.Unmarshal(b, &v)
 }

internal/encoding/yaml/codec_test.go

@@ -0,0 +1,136 @@
+package yaml
+
+import (
+	"reflect"
+	"testing"
+)
+
+// original form of the data
+const original = `# key-value pair
+key: value
+list:
+    - item1
+    - item2
+    - item3
+map:
+    key: value
+
+# nested
+# map
+nested_map:
+    map:
+        key: value
+        list:
+            - item1
+            - item2
+            - item3
+`
+
+// encoded form of the data
+const encoded = `key: value
+list:
+    - item1
+    - item2
+    - item3
+map:
+    key: value
+nested_map:
+    map:
+        key: value
+        list:
+            - item1
+            - item2
+            - item3
+`
+
+// decoded form of the data
+//
+// in case of YAML it's slightly different from Viper's internal representation
+// (eg. map is decoded into a map with interface key)
+var decoded = map[string]interface{}{
+	"key": "value",
+	"list": []interface{}{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+	"nested_map": map[string]interface{}{
+		"map": map[string]interface{}{
+			"key": "value",
+			"list": []interface{}{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+// Viper's internal representation
+var data = map[string]interface{}{
+	"key": "value",
+	"list": []interface{}{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]interface{}{
+		"key": "value",
+	},
+	"nested_map": map[string]interface{}{
+		"map": map[string]interface{}{
+			"key": "value",
+			"list": []interface{}{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if encoded != string(b) {
+		t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", string(b), encoded)
+	}
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(original), v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(decoded, v) {
+			t.Fatalf("decoded value does not match the expected one\nactual:   %#v\nexpected: %#v", v, decoded)
+		}
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]interface{}{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		if err == nil {
+			t.Fatal("expected decoding to fail")
+		}
+
+		t.Logf("decoding failed as expected: %s", err)
+	})
+}

internal/testutil/env_go1_16.go

@@ -1,3 +1,6 @@
+//go:build !go1.17
+// +build !go1.17
+
 package testutil
 
 import (
@@ -18,11 +21,6 @@ func Setenv(t *testing.T, name, val string) {
 	setenv(t, name, val, true)
 }
 
-// Unsetenv unsets an environment variable for the duration of a test.
-func Unsetenv(t *testing.T, name string) {
-	setenv(t, name, "", false)
-}
-
 // setenv sets or unsets an environment variable to a temporary value for the
 // duration of the test
 func setenv(t *testing.T, name, val string, valOK bool) {

internal/testutil/env_go1_17.go

@@ -0,0 +1,18 @@
+//go:build go1.17
+// +build go1.17
+
+package testutil
+
+import (
+	"testing"
+)
+
+// Setenv sets an environment variable to a temporary value for the
+// duration of the test.
+//
+// This shim can be removed once support for Go <1.17 is dropped.
+func Setenv(t *testing.T, name, val string) {
+	t.Helper()
+
+	t.Setenv(name, val)
+}

internal/testutil/filepath.go

@@ -0,0 +1,18 @@
+package testutil
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+// AbsFilePath calls filepath.Abs on path.
+func AbsFilePath(t *testing.T, path string) string {
+	t.Helper()
+
+	s, err := filepath.Abs(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return s
+}

logger.go

@@ -0,0 +1,77 @@
+package viper
+
+import (
+	"fmt"
+
+	jww "github.com/spf13/jwalterweatherman"
+)
+
+// Logger is a unified interface for various logging use cases and practices, including:
+//   - leveled logging
+//   - structured logging
+type Logger interface {
+	// Trace logs a Trace event.
+	//
+	// Even more fine-grained information than Debug events.
+	// Loggers not supporting this level should fall back to Debug.
+	Trace(msg string, keyvals ...interface{})
+
+	// Debug logs a Debug event.
+	//
+	// A verbose series of information events.
+	// They are useful when debugging the system.
+	Debug(msg string, keyvals ...interface{})
+
+	// Info logs an Info event.
+	//
+	// General information about what's happening inside the system.
+	Info(msg string, keyvals ...interface{})
+
+	// Warn logs a Warn(ing) event.
+	//
+	// Non-critical events that should be looked at.
+	Warn(msg string, keyvals ...interface{})
+
+	// Error logs an Error event.
+	//
+	// Critical events that require immediate attention.
+	// Loggers commonly provide Fatal and Panic levels above Error level,
+	// but exiting and panicing is out of scope for a logging library.
+	Error(msg string, keyvals ...interface{})
+}
+
+type jwwLogger struct{}
+
+func (jwwLogger) Trace(msg string, keyvals ...interface{}) {
+	jww.TRACE.Printf(jwwLogMessage(msg, keyvals...))
+}
+
+func (jwwLogger) Debug(msg string, keyvals ...interface{}) {
+	jww.DEBUG.Printf(jwwLogMessage(msg, keyvals...))
+}
+
+func (jwwLogger) Info(msg string, keyvals ...interface{}) {
+	jww.INFO.Printf(jwwLogMessage(msg, keyvals...))
+}
+
+func (jwwLogger) Warn(msg string, keyvals ...interface{}) {
+	jww.WARN.Printf(jwwLogMessage(msg, keyvals...))
+}
+
+func (jwwLogger) Error(msg string, keyvals ...interface{}) {
+	jww.ERROR.Printf(jwwLogMessage(msg, keyvals...))
+}
+
+func jwwLogMessage(msg string, keyvals ...interface{}) string {
+	out := msg
+
+	if len(keyvals) > 0 && len(keyvals)%2 == 1 {
+		keyvals = append(keyvals, nil)
+	}
+
+	for i := 0; i <= len(keyvals)-2; i += 2 {
+		out = fmt.Sprintf("%s %v=%v", out, keyvals[i], keyvals[i+1])
+	}
+
+	return out
+}

remote/remote.go

@@ -10,8 +10,9 @@ import (
 	"bytes"
 	"io"
 	"os"
+	"strings"
 
-	crypt "github.com/bketelsen/crypt/config"
+	crypt "github.com/sagikazarmark/crypt/config"
 
 	"github.com/spf13/viper"
 )
@@ -75,6 +76,7 @@ func getConfigManager(rp viper.RemoteProvider) (crypt.ConfigManager, error) {
 	var cm crypt.ConfigManager
 	var err error
 
+	endpoints := strings.Split(rp.Endpoint(), ";")
 	if rp.SecretKeyring() != "" {
 		var kr *os.File
 		kr, err = os.Open(rp.SecretKeyring())
@@ -84,20 +86,24 @@ func getConfigManager(rp viper.RemoteProvider) (crypt.ConfigManager, error) {
 		defer kr.Close()
 		switch rp.Provider() {
 		case "etcd":
-			cm, err = crypt.NewEtcdConfigManager([]string{rp.Endpoint()}, kr)
+			cm, err = crypt.NewEtcdConfigManager(endpoints, kr)
+		case "etcd3":
+			cm, err = crypt.NewEtcdV3ConfigManager(endpoints, kr)
 		case "firestore":
-			cm, err = crypt.NewFirestoreConfigManager([]string{rp.Endpoint()}, kr)
+			cm, err = crypt.NewFirestoreConfigManager(endpoints, kr)
 		default:
-			cm, err = crypt.NewConsulConfigManager([]string{rp.Endpoint()}, kr)
+			cm, err = crypt.NewConsulConfigManager(endpoints, kr)
 		}
 	} else {
 		switch rp.Provider() {
 		case "etcd":
-			cm, err = crypt.NewStandardEtcdConfigManager([]string{rp.Endpoint()})
+			cm, err = crypt.NewStandardEtcdConfigManager(endpoints)
+		case "etcd3":
+			cm, err = crypt.NewStandardEtcdV3ConfigManager(endpoints)
 		case "firestore":
-			cm, err = crypt.NewStandardFirestoreConfigManager([]string{rp.Endpoint()})
+			cm, err = crypt.NewStandardFirestoreConfigManager(endpoints)
 		default:
-			cm, err = crypt.NewStandardConsulConfigManager([]string{rp.Endpoint()})
+			cm, err = crypt.NewStandardConsulConfigManager(endpoints)
 		}
 	}
 	if err != nil {

util.go

@@ -18,9 +18,7 @@ import (
 	"strings"
 	"unicode"
 
-	"github.com/spf13/afero"
 	"github.com/spf13/cast"
-	jww "github.com/spf13/jwalterweatherman"
 )
 
 // ConfigParseError denotes failing to parse configuration file.
@@ -66,18 +64,25 @@ func copyAndInsensitiviseMap(m map[string]interface{}) map[string]interface{} {
 	return nm
 }
 
+func insensitiviseVal(val interface{}) interface{} {
+	switch val.(type) {
+	case map[interface{}]interface{}:
+		// nested map: cast and recursively insensitivise
+		val = cast.ToStringMap(val)
+		insensitiviseMap(val.(map[string]interface{}))
+	case map[string]interface{}:
+		// nested map: recursively insensitivise
+		insensitiviseMap(val.(map[string]interface{}))
+	case []interface{}:
+		// nested array: recursively insensitivise
+		insensitiveArray(val.([]interface{}))
+	}
+	return val
+}
+
 func insensitiviseMap(m map[string]interface{}) {
 	for key, val := range m {
-		switch val.(type) {
-		case map[interface{}]interface{}:
-			// nested map: cast and recursively insensitivise
-			val = cast.ToStringMap(val)
-			insensitiviseMap(val.(map[string]interface{}))
-		case map[string]interface{}:
-			// nested map: recursively insensitivise
-			insensitiviseMap(val.(map[string]interface{}))
-		}
-
+		val = insensitiviseVal(val)
 		lower := strings.ToLower(key)
 		if key != lower {
 			// remove old key (not lower-cased)
@@ -88,26 +93,20 @@ func insensitiviseMap(m map[string]interface{}) {
 	}
 }
 
-func absPathify(inPath string) string {
-	jww.INFO.Println("Trying to resolve absolute path to", inPath)
+func insensitiveArray(a []interface{}) {
+	for i, val := range a {
+		a[i] = insensitiviseVal(val)
+	}
+}
+
+func absPathify(logger Logger, inPath string) string {
+	logger.Info("trying to resolve absolute path", "path", inPath)
 
 	if inPath == "$HOME" || strings.HasPrefix(inPath, "$HOME"+string(os.PathSeparator)) {
 		inPath = userHomeDir() + inPath[5:]
 	}
 
-	if strings.HasPrefix(inPath, "$") {
-		end := strings.Index(inPath, string(os.PathSeparator))
-
-		var value, suffix string
-		if end == -1 {
-			value = os.Getenv(inPath[1:])
-		} else {
-			value = os.Getenv(inPath[1:end])
-			suffix = inPath[end:]
-		}
-
-		inPath = value + suffix
-	}
+	inPath = os.ExpandEnv(inPath)
 
 	if filepath.IsAbs(inPath) {
 		return filepath.Clean(inPath)
@@ -118,21 +117,9 @@ func absPathify(inPath string) string {
 		return filepath.Clean(p)
 	}
 
-	jww.ERROR.Println("Couldn't discover absolute path")
-	jww.ERROR.Println(err)
-	return ""
-}
+	logger.Error(fmt.Errorf("could not discover absolute path: %w", err).Error())
 
-// Check if file Exists
-func exists(fs afero.Fs, path string) (bool, error) {
-	stat, err := fs.Stat(path)
-	if err == nil {
-		return !stat.IsDir(), nil
-	}
-	if os.IsNotExist(err) {
-		return false, nil
-	}
-	return false, err
+	return ""
 }
 
 func stringInSlice(a string, list []string) bool {

util_test.go

@@ -58,6 +58,8 @@ func TestCopyAndInsensitiviseMap(t *testing.T) {
 }
 
 func TestAbsPathify(t *testing.T) {
+	skipWindows(t)
+
 	home := userHomeDir()
 	homer := filepath.Join(home, "homer")
 	wd, _ := os.Getwd()
@@ -85,7 +87,7 @@ func TestAbsPathify(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		got := absPathify(test.input)
+		got := absPathify(jwwLogger{}, test.input)
 		if got != test.output {
 			t.Errorf("Got %v\nexpected\n%q", got, test.output)
 		}

viper.go

@@ -35,17 +35,16 @@ import (
 	"time"
 
 	"github.com/fsnotify/fsnotify"
-	"github.com/magiconair/properties"
 	"github.com/mitchellh/mapstructure"
 	"github.com/spf13/afero"
 	"github.com/spf13/cast"
-	jww "github.com/spf13/jwalterweatherman"
 	"github.com/spf13/pflag"
-	"github.com/subosito/gotenv"
-	"gopkg.in/ini.v1"
 
 	"github.com/spf13/viper/internal/encoding"
+	"github.com/spf13/viper/internal/encoding/dotenv"
 	"github.com/spf13/viper/internal/encoding/hcl"
+	"github.com/spf13/viper/internal/encoding/ini"
+	"github.com/spf13/viper/internal/encoding/javaproperties"
 	"github.com/spf13/viper/internal/encoding/json"
 	"github.com/spf13/viper/internal/encoding/toml"
 	"github.com/spf13/viper/internal/encoding/yaml"
@@ -68,44 +67,8 @@ type RemoteResponse struct {
 	Error error
 }
 
-var (
-	encoderRegistry = encoding.NewEncoderRegistry()
-	decoderRegistry = encoding.NewDecoderRegistry()
-)
-
 func init() {
 	v = New()
-
-	{
-		codec := yaml.Codec{}
-
-		encoderRegistry.RegisterEncoder("yaml", codec)
-		decoderRegistry.RegisterDecoder("yaml", codec)
-
-		encoderRegistry.RegisterEncoder("yml", codec)
-		decoderRegistry.RegisterDecoder("yml", codec)
-	}
-
-	{
-		codec := json.Codec{}
-
-		encoderRegistry.RegisterEncoder("json", codec)
-		decoderRegistry.RegisterDecoder("json", codec)
-	}
-
-	{
-		codec := toml.Codec{}
-
-		encoderRegistry.RegisterEncoder("toml", codec)
-		decoderRegistry.RegisterDecoder("toml", codec)
-	}
-
-	{
-		codec := hcl.Codec{}
-
-		encoderRegistry.RegisterEncoder("hcl", codec)
-		decoderRegistry.RegisterDecoder("hcl", codec)
-	}
 }
 
 type remoteConfigFactory interface {
@@ -169,10 +132,10 @@ type DecoderConfigOption func(*mapstructure.DecoderConfig)
 // DecodeHook returns a DecoderConfigOption which overrides the default
 // DecoderConfig.DecodeHook value, the default is:
 //
-//  mapstructure.ComposeDecodeHookFunc(
-//		mapstructure.StringToTimeDurationHookFunc(),
-//		mapstructure.StringToSliceHookFunc(","),
-//	)
+//	 mapstructure.ComposeDecodeHookFunc(
+//			mapstructure.StringToTimeDurationHookFunc(),
+//			mapstructure.StringToSliceHookFunc(","),
+//		)
 func DecodeHook(hook mapstructure.DecodeHookFunc) DecoderConfigOption {
 	return func(c *mapstructure.DecoderConfig) {
 		c.DecodeHook = hook
@@ -193,18 +156,18 @@ func DecodeHook(hook mapstructure.DecodeHookFunc) DecoderConfigOption {
 //
 // For example, if values from the following sources were loaded:
 //
-//  Defaults : {
-//  	"secret": "",
-//  	"user": "default",
-//  	"endpoint": "https://localhost"
-//  }
-//  Config : {
-//  	"user": "root"
-//  	"secret": "defaultsecret"
-//  }
-//  Env : {
-//  	"secret": "somesecretkey"
-//  }
+//	Defaults : {
+//		"secret": "",
+//		"user": "default",
+//		"endpoint": "https://localhost"
+//	}
+//	Config : {
+//		"user": "root"
+//		"secret": "defaultsecret"
+//	}
+//	Env : {
+//		"secret": "somesecretkey"
+//	}
 //
 // The resulting config will have the following values:
 //
@@ -252,11 +215,13 @@ type Viper struct {
 	aliases        map[string]string
 	typeByDefValue bool
 
-	// Store read properties on the object so that we can write back in order with comments.
-	// This will only be used if the configuration read is a properties file.
-	properties *properties.Properties
-
 	onConfigChange func(fsnotify.Event)
+
+	logger Logger
+
+	// TODO: should probably be protected with a mutex
+	encoderRegistry *encoding.EncoderRegistry
+	decoderRegistry *encoding.DecoderRegistry
 }
 
 // New returns an initialized Viper instance.
@@ -264,7 +229,7 @@ func New() *Viper {
 	v := new(Viper)
 	v.keyDelim = "."
 	v.configName = "config"
-	v.configPermissions = os.FileMode(0644)
+	v.configPermissions = os.FileMode(0o644)
 	v.fs = afero.NewOsFs()
 	v.config = make(map[string]interface{})
 	v.override = make(map[string]interface{})
@@ -274,6 +239,9 @@ func New() *Viper {
 	v.env = make(map[string][]string)
 	v.aliases = make(map[string]string)
 	v.typeByDefValue = false
+	v.logger = jwwLogger{}
+
+	v.resetEncoding()
 
 	return v
 }
@@ -321,6 +289,8 @@ func NewWithOptions(opts ...Option) *Viper {
 		opt.apply(v)
 	}
 
+	v.resetEncoding()
+
 	return v
 }
 
@@ -329,8 +299,86 @@ func NewWithOptions(opts ...Option) *Viper {
 // can use it in their testing as well.
 func Reset() {
 	v = New()
-	SupportedExts = []string{"json", "toml", "yaml", "yml", "properties", "props", "prop", "hcl", "dotenv", "env", "ini"}
-	SupportedRemoteProviders = []string{"etcd", "consul", "firestore"}
+	SupportedExts = []string{"json", "toml", "yaml", "yml", "properties", "props", "prop", "hcl", "tfvars", "dotenv", "env", "ini"}
+	SupportedRemoteProviders = []string{"etcd", "etcd3", "consul", "firestore"}
+}
+
+// TODO: make this lazy initialization instead
+func (v *Viper) resetEncoding() {
+	encoderRegistry := encoding.NewEncoderRegistry()
+	decoderRegistry := encoding.NewDecoderRegistry()
+
+	{
+		codec := yaml.Codec{}
+
+		encoderRegistry.RegisterEncoder("yaml", codec)
+		decoderRegistry.RegisterDecoder("yaml", codec)
+
+		encoderRegistry.RegisterEncoder("yml", codec)
+		decoderRegistry.RegisterDecoder("yml", codec)
+	}
+
+	{
+		codec := json.Codec{}
+
+		encoderRegistry.RegisterEncoder("json", codec)
+		decoderRegistry.RegisterDecoder("json", codec)
+	}
+
+	{
+		codec := toml.Codec{}
+
+		encoderRegistry.RegisterEncoder("toml", codec)
+		decoderRegistry.RegisterDecoder("toml", codec)
+	}
+
+	{
+		codec := hcl.Codec{}
+
+		encoderRegistry.RegisterEncoder("hcl", codec)
+		decoderRegistry.RegisterDecoder("hcl", codec)
+
+		encoderRegistry.RegisterEncoder("tfvars", codec)
+		decoderRegistry.RegisterDecoder("tfvars", codec)
+	}
+
+	{
+		codec := ini.Codec{
+			KeyDelimiter: v.keyDelim,
+			LoadOptions:  v.iniLoadOptions,
+		}
+
+		encoderRegistry.RegisterEncoder("ini", codec)
+		decoderRegistry.RegisterDecoder("ini", codec)
+	}
+
+	{
+		codec := &javaproperties.Codec{
+			KeyDelimiter: v.keyDelim,
+		}
+
+		encoderRegistry.RegisterEncoder("properties", codec)
+		decoderRegistry.RegisterDecoder("properties", codec)
+
+		encoderRegistry.RegisterEncoder("props", codec)
+		decoderRegistry.RegisterDecoder("props", codec)
+
+		encoderRegistry.RegisterEncoder("prop", codec)
+		decoderRegistry.RegisterDecoder("prop", codec)
+	}
+
+	{
+		codec := &dotenv.Codec{}
+
+		encoderRegistry.RegisterEncoder("dotenv", codec)
+		decoderRegistry.RegisterDecoder("dotenv", codec)
+
+		encoderRegistry.RegisterEncoder("env", codec)
+		decoderRegistry.RegisterDecoder("env", codec)
+	}
+
+	v.encoderRegistry = encoderRegistry
+	v.decoderRegistry = decoderRegistry
 }
 
 type defaultRemoteProvider struct {
@@ -368,18 +416,23 @@ type RemoteProvider interface {
 }
 
 // SupportedExts are universally supported extensions.
-var SupportedExts = []string{"json", "toml", "yaml", "yml", "properties", "props", "prop", "hcl", "dotenv", "env", "ini"}
+var SupportedExts = []string{"json", "toml", "yaml", "yml", "properties", "props", "prop", "hcl", "tfvars", "dotenv", "env", "ini"}
 
 // SupportedRemoteProviders are universally supported remote providers.
-var SupportedRemoteProviders = []string{"etcd", "consul", "firestore"}
+var SupportedRemoteProviders = []string{"etcd", "etcd3", "consul", "firestore"}
 
+// OnConfigChange sets the event handler that is called when a config file changes.
 func OnConfigChange(run func(in fsnotify.Event)) { v.OnConfigChange(run) }
+
+// OnConfigChange sets the event handler that is called when a config file changes.
 func (v *Viper) OnConfigChange(run func(in fsnotify.Event)) {
 	v.onConfigChange = run
 }
 
+// WatchConfig starts watching a config file for changes.
 func WatchConfig() { v.WatchConfig() }
 
+// WatchConfig starts watching a config file for changes.
 func (v *Viper) WatchConfig() {
 	initWG := sync.WaitGroup{}
 	initWG.Add(1)
@@ -415,9 +468,8 @@ func (v *Viper) WatchConfig() {
 					// we only care about the config file with the following cases:
 					// 1 - if the config file was modified or created
 					// 2 - if the real path to the config file changed (eg: k8s ConfigMap replacement)
-					const writeOrCreateMask = fsnotify.Write | fsnotify.Create
 					if (filepath.Clean(event.Name) == configFile &&
-						event.Op&writeOrCreateMask != 0) ||
+						(event.Has(fsnotify.Write) || event.Has(fsnotify.Create))) ||
 						(currentConfigFile != "" && currentConfigFile != realConfigFile) {
 						realConfigFile = currentConfigFile
 						err := v.ReadInConfig()
@@ -427,8 +479,7 @@ func (v *Viper) WatchConfig() {
 						if v.onConfigChange != nil {
 							v.onConfigChange(event)
 						}
-					} else if filepath.Clean(event.Name) == configFile &&
-						event.Op&fsnotify.Remove&fsnotify.Remove != 0 {
+					} else if filepath.Clean(event.Name) == configFile && event.Has(fsnotify.Remove) {
 						eventsWG.Done()
 						return
 					}
@@ -514,8 +565,9 @@ func AddConfigPath(in string) { v.AddConfigPath(in) }
 
 func (v *Viper) AddConfigPath(in string) {
 	if in != "" {
-		absin := absPathify(in)
-		jww.INFO.Println("adding", absin, "to paths to search")
+		absin := absPathify(v.logger, in)
+
+		v.logger.Info("adding path to search paths", "path", absin)
 		if !stringInSlice(absin, v.configPaths) {
 			v.configPaths = append(v.configPaths, absin)
 		}
@@ -524,7 +576,7 @@ func (v *Viper) AddConfigPath(in string) {
 
 // AddRemoteProvider adds a remote configuration source.
 // Remote Providers are searched in the order they are added.
-// provider is a string value: "etcd", "consul" or "firestore" are currently supported.
+// provider is a string value: "etcd", "etcd3", "consul" or "firestore" are currently supported.
 // endpoint is the url.  etcd requires http://ip:port  consul requires ip:port
 // path is the path in the k/v store to retrieve configuration
 // To retrieve a config file called myapp.json from /configs/myapp.json
@@ -539,7 +591,8 @@ func (v *Viper) AddRemoteProvider(provider, endpoint, path string) error {
 		return UnsupportedRemoteProviderError(provider)
 	}
 	if provider != "" && endpoint != "" {
-		jww.INFO.Printf("adding %s:%s to remote provider list", provider, endpoint)
+		v.logger.Info("adding remote provider", "provider", provider, "endpoint", endpoint)
+
 		rp := &defaultRemoteProvider{
 			endpoint: endpoint,
 			provider: provider,
@@ -554,7 +607,7 @@ func (v *Viper) AddRemoteProvider(provider, endpoint, path string) error {
 
 // AddSecureRemoteProvider adds a remote configuration source.
 // Secure Remote Providers are searched in the order they are added.
-// provider is a string value: "etcd", "consul" or "firestore" are currently supported.
+// provider is a string value: "etcd", "etcd3", "consul" or "firestore" are currently supported.
 // endpoint is the url.  etcd requires http://ip:port  consul requires ip:port
 // secretkeyring is the filepath to your openpgp secret keyring.  e.g. /etc/secrets/myring.gpg
 // path is the path in the k/v store to retrieve configuration
@@ -571,7 +624,8 @@ func (v *Viper) AddSecureRemoteProvider(provider, endpoint, path, secretkeyring
 		return UnsupportedRemoteProviderError(provider)
 	}
 	if provider != "" && endpoint != "" {
-		jww.INFO.Printf("adding %s:%s to remote provider list", provider, endpoint)
+		v.logger.Info("adding remote provider", "provider", provider, "endpoint", endpoint)
+
 		rp := &defaultRemoteProvider{
 			endpoint:      endpoint,
 			provider:      provider,
@@ -734,7 +788,8 @@ func (v *Viper) searchMapWithPathPrefixes(
 // isPathShadowedInDeepMap makes sure the given path is not shadowed somewhere
 // on its path in the map.
 // e.g., if "foo.bar" has a value in the given map, it “shadows”
-//       "foo.bar.baz" in a lower-priority map
+//
+//	"foo.bar.baz" in a lower-priority map
 func (v *Viper) isPathShadowedInDeepMap(path []string, m map[string]interface{}) string {
 	var parentVal interface{}
 	for i := 1; i < len(path); i++ {
@@ -759,7 +814,8 @@ func (v *Viper) isPathShadowedInDeepMap(path []string, m map[string]interface{})
 // isPathShadowedInFlatMap makes sure the given path is not shadowed somewhere
 // in a sub-path of the map.
 // e.g., if "foo.bar" has a value in the given map, it “shadows”
-//       "foo.bar.baz" in a lower-priority map
+//
+//	"foo.bar.baz" in a lower-priority map
 func (v *Viper) isPathShadowedInFlatMap(path []string, mi interface{}) string {
 	// unify input map
 	var m map[string]interface{}
@@ -784,7 +840,8 @@ func (v *Viper) isPathShadowedInFlatMap(path []string, mi interface{}) string {
 // isPathShadowedInAutoEnv makes sure the given path is not shadowed somewhere
 // in the environment, when automatic env is on.
 // e.g., if "foo.bar" has a value in the environment, it “shadows”
-//       "foo.bar.baz" in a lower-priority map
+//
+//	"foo.bar.baz" in a lower-priority map
 func (v *Viper) isPathShadowedInAutoEnv(path []string) string {
 	var parentKey string
 	for i := 1; i < len(path); i++ {
@@ -805,11 +862,11 @@ func (v *Viper) isPathShadowedInAutoEnv(path []string) string {
 // would return a string slice for the key if the key's type is inferred by
 // the default value and the Get function would return:
 //
-//   []string {"a", "b", "c"}
+//	[]string {"a", "b", "c"}
 //
 // Otherwise the Get function would return:
 //
-//   "a b c"
+//	"a b c"
 func SetTypeByDefaultValue(enable bool) { v.SetTypeByDefaultValue(enable) }
 
 func (v *Viper) SetTypeByDefaultValue(enable bool) {
@@ -937,6 +994,13 @@ func (v *Viper) GetUint(key string) uint {
 	return cast.ToUint(v.Get(key))
 }
 
+// GetUint16 returns the value associated with the key as an unsigned integer.
+func GetUint16(key string) uint16 { return v.GetUint16(key) }
+
+func (v *Viper) GetUint16(key string) uint16 {
+	return cast.ToUint16(v.Get(key))
+}
+
 // GetUint32 returns the value associated with the key as an unsigned integer.
 func GetUint32(key string) uint32 { return v.GetUint32(key) }
 
@@ -1086,9 +1150,8 @@ func (v *Viper) BindPFlags(flags *pflag.FlagSet) error {
 // BindPFlag binds a specific key to a pflag (as used by cobra).
 // Example (where serverCmd is a Cobra instance):
 //
-//	 serverCmd.Flags().Int("port", 1138, "Port to run Application server on")
-//	 Viper.BindPFlag("port", serverCmd.Flags().Lookup("port"))
-//
+//	serverCmd.Flags().Int("port", 1138, "Port to run Application server on")
+//	Viper.BindPFlag("port", serverCmd.Flags().Lookup("port"))
 func BindPFlag(key string, flag *pflag.Flag) error { return v.BindPFlag(key, flag) }
 
 func (v *Viper) BindPFlag(key string, flag *pflag.Flag) error {
@@ -1146,6 +1209,17 @@ func (v *Viper) BindEnv(input ...string) error {
 	return nil
 }
 
+// MustBindEnv wraps BindEnv in a panic.
+// If there is an error binding an environment variable, MustBindEnv will
+// panic.
+func MustBindEnv(input ...string) { v.MustBindEnv(input...) }
+
+func (v *Viper) MustBindEnv(input ...string) {
+	if err := v.BindEnv(input...); err != nil {
+		panic(fmt.Sprintf("error while binding environment variable: %v", err))
+	}
+}
+
 // Given a key, find the value.
 //
 // Viper will check to see if an alias exists first.
@@ -1387,14 +1461,15 @@ func (v *Viper) registerAlias(alias string, key string) {
 			v.aliases[alias] = key
 		}
 	} else {
-		jww.WARN.Println("Creating circular reference alias", alias, key, v.realKey(key))
+		v.logger.Warn("creating circular reference alias", "alias", alias, "key", key, "real_key", v.realKey(key))
 	}
 }
 
 func (v *Viper) realKey(key string) string {
 	newkey, exists := v.aliases[key]
 	if exists {
-		jww.DEBUG.Println("Alias", key, "to", newkey)
+		v.logger.Debug("key is an alias", "alias", key, "to", newkey)
+
 		return v.realKey(newkey)
 	}
 	return key
@@ -1404,11 +1479,13 @@ func (v *Viper) realKey(key string) string {
 func InConfig(key string) bool { return v.InConfig(key) }
 
 func (v *Viper) InConfig(key string) bool {
-	// if the requested key is an alias, then return the proper key
-	key = v.realKey(key)
+	lcaseKey := strings.ToLower(key)
 
-	_, exists := v.config[key]
-	return exists
+	// if the requested key is an alias, then return the proper key
+	lcaseKey = v.realKey(lcaseKey)
+	path := strings.Split(lcaseKey, v.keyDelim)
+
+	return v.searchIndexableWithPathPrefixes(v.config, path) != nil
 }
 
 // SetDefault sets the default value for this key.
@@ -1453,7 +1530,7 @@ func (v *Viper) Set(key string, value interface{}) {
 func ReadInConfig() error { return v.ReadInConfig() }
 
 func (v *Viper) ReadInConfig() error {
-	jww.INFO.Println("Attempting to read in config file")
+	v.logger.Info("attempting to read in config file")
 	filename, err := v.getConfigFile()
 	if err != nil {
 		return err
@@ -1463,7 +1540,7 @@ func (v *Viper) ReadInConfig() error {
 		return UnsupportedConfigError(v.getConfigType())
 	}
 
-	jww.DEBUG.Println("Reading file: ", filename)
+	v.logger.Debug("reading file", "file", filename)
 	file, err := afero.ReadFile(v.fs, filename)
 	if err != nil {
 		return err
@@ -1484,7 +1561,7 @@ func (v *Viper) ReadInConfig() error {
 func MergeInConfig() error { return v.MergeInConfig() }
 
 func (v *Viper) MergeInConfig() error {
-	jww.INFO.Println("Attempting to merge in config file")
+	v.logger.Info("attempting to merge in config file")
 	filename, err := v.getConfigFile()
 	if err != nil {
 		return err
@@ -1575,11 +1652,12 @@ func (v *Viper) SafeWriteConfigAs(filename string) error {
 }
 
 func (v *Viper) writeConfig(filename string, force bool) error {
-	jww.INFO.Println("Attempting to write configuration to file.")
+	v.logger.Info("attempting to write configuration to file")
+
 	var configType string
 
 	ext := filepath.Ext(filename)
-	if ext != "" {
+	if ext != "" && ext != filepath.Base(filename) {
 		configType = ext[1:]
 	} else {
 		configType = v.configType
@@ -1622,53 +1700,11 @@ func (v *Viper) unmarshalReader(in io.Reader, c map[string]interface{}) error {
 	buf.ReadFrom(in)
 
 	switch format := strings.ToLower(v.getConfigType()); format {
-	case "yaml", "yml", "json", "toml", "hcl":
-		err := decoderRegistry.Decode(format, buf.Bytes(), &c)
+	case "yaml", "yml", "json", "toml", "hcl", "tfvars", "ini", "properties", "props", "prop", "dotenv", "env":
+		err := v.decoderRegistry.Decode(format, buf.Bytes(), c)
 		if err != nil {
 			return ConfigParseError{err}
 		}
-
-	case "dotenv", "env":
-		env, err := gotenv.StrictParse(buf)
-		if err != nil {
-			return ConfigParseError{err}
-		}
-		for k, v := range env {
-			c[k] = v
-		}
-
-	case "properties", "props", "prop":
-		v.properties = properties.NewProperties()
-		var err error
-		if v.properties, err = properties.Load(buf.Bytes(), properties.UTF8); err != nil {
-			return ConfigParseError{err}
-		}
-		for _, key := range v.properties.Keys() {
-			value, _ := v.properties.Get(key)
-			// recursively build nested maps
-			path := strings.Split(key, ".")
-			lastKey := strings.ToLower(path[len(path)-1])
-			deepestMap := deepSearch(c, path[0:len(path)-1])
-			// set innermost value
-			deepestMap[lastKey] = value
-		}
-
-	case "ini":
-		cfg := ini.Empty(v.iniLoadOptions)
-		err := cfg.Append(buf.Bytes())
-		if err != nil {
-			return ConfigParseError{err}
-		}
-		sections := cfg.Sections()
-		for i := 0; i < len(sections); i++ {
-			section := sections[i]
-			keys := section.Keys()
-			for j := 0; j < len(keys); j++ {
-				key := keys[j]
-				value := cfg.Section(section.Name()).Key(key.Name()).String()
-				c[section.Name()+"."+key.Name()] = value
-			}
-		}
 	}
 
 	insensitiviseMap(c)
@@ -1679,8 +1715,8 @@ func (v *Viper) unmarshalReader(in io.Reader, c map[string]interface{}) error {
 func (v *Viper) marshalWriter(f afero.File, configType string) error {
 	c := v.AllSettings()
 	switch configType {
-	case "yaml", "yml", "json", "toml", "hcl":
-		b, err := encoderRegistry.Encode(configType, c)
+	case "yaml", "yml", "json", "toml", "hcl", "tfvars", "ini", "prop", "props", "properties", "dotenv", "env":
+		b, err := v.encoderRegistry.Encode(configType, c)
 		if err != nil {
 			return ConfigMarshalError{err}
 		}
@@ -1689,50 +1725,6 @@ func (v *Viper) marshalWriter(f afero.File, configType string) error {
 		if err != nil {
 			return ConfigMarshalError{err}
 		}
-
-	case "prop", "props", "properties":
-		if v.properties == nil {
-			v.properties = properties.NewProperties()
-		}
-		p := v.properties
-		for _, key := range v.AllKeys() {
-			_, _, err := p.Set(key, v.GetString(key))
-			if err != nil {
-				return ConfigMarshalError{err}
-			}
-		}
-		_, err := p.WriteComment(f, "#", properties.UTF8)
-		if err != nil {
-			return ConfigMarshalError{err}
-		}
-
-	case "dotenv", "env":
-		lines := []string{}
-		for _, key := range v.AllKeys() {
-			envName := strings.ToUpper(strings.Replace(key, ".", "_", -1))
-			val := v.Get(key)
-			lines = append(lines, fmt.Sprintf("%v=%v", envName, val))
-		}
-		s := strings.Join(lines, "\n")
-		if _, err := f.WriteString(s); err != nil {
-			return ConfigMarshalError{err}
-		}
-
-	case "ini":
-		keys := v.AllKeys()
-		cfg := ini.Empty()
-		ini.PrettyFormat = false
-		for i := 0; i < len(keys); i++ {
-			key := keys[i]
-			lastSep := strings.LastIndex(key, ".")
-			sectionName := key[:(lastSep)]
-			keyName := key[(lastSep + 1):]
-			if sectionName == "default" {
-				sectionName = ""
-			}
-			cfg.Section(sectionName).Key(keyName).SetValue(v.GetString(key))
-		}
-		cfg.WriteTo(f)
 	}
 	return nil
 }
@@ -1749,7 +1741,8 @@ func keyExists(k string, m map[string]interface{}) string {
 }
 
 func castToMapStringInterface(
-	src map[interface{}]interface{}) map[string]interface{} {
+	src map[interface{}]interface{},
+) map[string]interface{} {
 	tgt := map[string]interface{}{}
 	for k, v := range src {
 		tgt[fmt.Sprintf("%v", k)] = v
@@ -1787,11 +1780,12 @@ func castMapFlagToMapInterface(src map[string]FlagValue) map[string]interface{}
 // deep. Both map types are supported as there is a go-yaml fork that uses
 // `map[string]interface{}` instead.
 func mergeMaps(
-	src, tgt map[string]interface{}, itgt map[interface{}]interface{}) {
+	src, tgt map[string]interface{}, itgt map[interface{}]interface{},
+) {
 	for sk, sv := range src {
 		tk := keyExists(sk, tgt)
 		if tk == "" {
-			jww.TRACE.Printf("tk=\"\", tgt[%s]=%v", sk, sv)
+			v.logger.Trace("", "tk", "\"\"", fmt.Sprintf("tgt[%s]", sk), sv)
 			tgt[sk] = sv
 			if itgt != nil {
 				itgt[sk] = sv
@@ -1801,7 +1795,7 @@ func mergeMaps(
 
 		tv, ok := tgt[tk]
 		if !ok {
-			jww.TRACE.Printf("tgt[%s] != ok, tgt[%s]=%v", tk, sk, sv)
+			v.logger.Trace("", fmt.Sprintf("ok[%s]", tk), false, fmt.Sprintf("tgt[%s]", sk), sv)
 			tgt[sk] = sv
 			if itgt != nil {
 				itgt[sk] = sv
@@ -1811,28 +1805,52 @@ func mergeMaps(
 
 		svType := reflect.TypeOf(sv)
 		tvType := reflect.TypeOf(tv)
-		if tvType != nil && svType != tvType { // Allow for the target to be nil
-			jww.ERROR.Printf(
-				"svType != tvType; key=%s, st=%v, tt=%v, sv=%v, tv=%v",
-				sk, svType, tvType, sv, tv)
-			continue
-		}
 
-		jww.TRACE.Printf("processing key=%s, st=%v, tt=%v, sv=%v, tv=%v",
-			sk, svType, tvType, sv, tv)
+		v.logger.Trace(
+			"processing",
+			"key", sk,
+			"st", svType,
+			"tt", tvType,
+			"sv", sv,
+			"tv", tv,
+		)
 
 		switch ttv := tv.(type) {
 		case map[interface{}]interface{}:
-			jww.TRACE.Printf("merging maps (must convert)")
-			tsv := sv.(map[interface{}]interface{})
+			v.logger.Trace("merging maps (must convert)")
+			tsv, ok := sv.(map[interface{}]interface{})
+			if !ok {
+				v.logger.Error(
+					"Could not cast sv to map[interface{}]interface{}",
+					"key", sk,
+					"st", svType,
+					"tt", tvType,
+					"sv", sv,
+					"tv", tv,
+				)
+				continue
+			}
+
 			ssv := castToMapStringInterface(tsv)
 			stv := castToMapStringInterface(ttv)
 			mergeMaps(ssv, stv, ttv)
 		case map[string]interface{}:
-			jww.TRACE.Printf("merging maps")
-			mergeMaps(sv.(map[string]interface{}), ttv, nil)
+			v.logger.Trace("merging maps")
+			tsv, ok := sv.(map[string]interface{})
+			if !ok {
+				v.logger.Error(
+					"Could not cast sv to map[string]interface{}",
+					"key", sk,
+					"st", svType,
+					"tt", tvType,
+					"sv", sv,
+					"tv", tv,
+				)
+				continue
+			}
+			mergeMaps(tsv, ttv, nil)
 		default:
-			jww.TRACE.Printf("setting value")
+			v.logger.Trace("setting value")
 			tgt[tk] = sv
 			if itgt != nil {
 				itgt[tk] = sv
@@ -1864,10 +1882,14 @@ func (v *Viper) getKeyValueConfig() error {
 		return RemoteConfigError("Enable the remote features by doing a blank import of the viper/remote package: '_ github.com/spf13/viper/remote'")
 	}
 
+	if len(v.remoteProviders) == 0 {
+		return RemoteConfigError("No Remote Providers")
+	}
+
 	for _, rp := range v.remoteProviders {
 		val, err := v.getRemoteConfig(rp)
 		if err != nil {
-			jww.ERROR.Printf("get remote config: %s", err)
+			v.logger.Error(fmt.Errorf("get remote config: %w", err).Error())
 
 			continue
 		}
@@ -1890,6 +1912,10 @@ func (v *Viper) getRemoteConfig(provider RemoteProvider) (map[string]interface{}
 
 // Retrieve the first found remote configuration.
 func (v *Viper) watchKeyValueConfigOnChannel() error {
+	if len(v.remoteProviders) == 0 {
+		return RemoteConfigError("No Remote Providers")
+	}
+
 	for _, rp := range v.remoteProviders {
 		respc, _ := RemoteConfig.WatchChannel(rp)
 		// Todo: Add quit channel
@@ -1907,9 +1933,15 @@ func (v *Viper) watchKeyValueConfigOnChannel() error {
 
 // Retrieve the first found remote configuration.
 func (v *Viper) watchKeyValueConfig() error {
+	if len(v.remoteProviders) == 0 {
+		return RemoteConfigError("No Remote Providers")
+	}
+
 	for _, rp := range v.remoteProviders {
 		val, err := v.watchRemoteConfig(rp)
 		if err != nil {
+			v.logger.Error(fmt.Errorf("watch remote config: %w", err).Error())
+
 			continue
 		}
 		v.kvstore = val
@@ -1952,9 +1984,10 @@ func (v *Viper) AllKeys() []string {
 
 // flattenAndMergeMap recursively flattens the given map into a map[string]bool
 // of key paths (used as a set, easier to manipulate than a []string):
-// - each path is merged into a single key string, delimited with v.keyDelim
-// - if a path is shadowed by an earlier value in the initial shadow map,
-//   it is skipped.
+//   - each path is merged into a single key string, delimited with v.keyDelim
+//   - if a path is shadowed by an earlier value in the initial shadow map,
+//     it is skipped.
+//
 // The resulting set of paths is merged to the given shadow set at the same time.
 func (v *Viper) flattenAndMergeMap(shadow map[string]bool, m map[string]interface{}, prefix string) map[string]bool {
 	if shadow != nil && prefix != "" && shadow[prefix] {
@@ -2103,49 +2136,19 @@ func (v *Viper) getConfigFile() (string, error) {
 	return v.configFile, nil
 }
 
-func (v *Viper) searchInPath(in string) (filename string) {
-	jww.DEBUG.Println("Searching for config in ", in)
-	for _, ext := range SupportedExts {
-		jww.DEBUG.Println("Checking for", filepath.Join(in, v.configName+"."+ext))
-		if b, _ := exists(v.fs, filepath.Join(in, v.configName+"."+ext)); b {
-			jww.DEBUG.Println("Found: ", filepath.Join(in, v.configName+"."+ext))
-			return filepath.Join(in, v.configName+"."+ext)
-		}
-	}
-
-	if v.configType != "" {
-		if b, _ := exists(v.fs, filepath.Join(in, v.configName)); b {
-			return filepath.Join(in, v.configName)
-		}
-	}
-
-	return ""
-}
-
-// Search all configPaths for any config file.
-// Returns the first path that exists (and is a config file).
-func (v *Viper) findConfigFile() (string, error) {
-	jww.INFO.Println("Searching for config in ", v.configPaths)
-
-	for _, cp := range v.configPaths {
-		file := v.searchInPath(cp)
-		if file != "" {
-			return file, nil
-		}
-	}
-	return "", ConfigFileNotFoundError{v.configName, fmt.Sprintf("%s", v.configPaths)}
-}
-
 // Debug prints all configuration registries for debugging
 // purposes.
-func Debug() { v.Debug() }
+func Debug()              { v.Debug() }
+func DebugTo(w io.Writer) { v.DebugTo(w) }
 
-func (v *Viper) Debug() {
-	fmt.Printf("Aliases:\n%#v\n", v.aliases)
-	fmt.Printf("Override:\n%#v\n", v.override)
-	fmt.Printf("PFlags:\n%#v\n", v.pflags)
-	fmt.Printf("Env:\n%#v\n", v.env)
-	fmt.Printf("Key/Value Store:\n%#v\n", v.kvstore)
-	fmt.Printf("Config:\n%#v\n", v.config)
-	fmt.Printf("Defaults:\n%#v\n", v.defaults)
+func (v *Viper) Debug() { v.DebugTo(os.Stdout) }
+
+func (v *Viper) DebugTo(w io.Writer) {
+	fmt.Fprintf(w, "Aliases:\n%#v\n", v.aliases)
+	fmt.Fprintf(w, "Override:\n%#v\n", v.override)
+	fmt.Fprintf(w, "PFlags:\n%#v\n", v.pflags)
+	fmt.Fprintf(w, "Env:\n%#v\n", v.env)
+	fmt.Fprintf(w, "Key/Value Store:\n%#v\n", v.kvstore)
+	fmt.Fprintf(w, "Config:\n%#v\n", v.config)
+	fmt.Fprintf(w, "Defaults:\n%#v\n", v.defaults)
 }

viper_go1_15.go

@@ -0,0 +1,57 @@
+//go:build !go1.16 || !finder
+// +build !go1.16 !finder
+
+package viper
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/spf13/afero"
+)
+
+// Search all configPaths for any config file.
+// Returns the first path that exists (and is a config file).
+func (v *Viper) findConfigFile() (string, error) {
+	v.logger.Info("searching for config in paths", "paths", v.configPaths)
+
+	for _, cp := range v.configPaths {
+		file := v.searchInPath(cp)
+		if file != "" {
+			return file, nil
+		}
+	}
+	return "", ConfigFileNotFoundError{v.configName, fmt.Sprintf("%s", v.configPaths)}
+}
+
+func (v *Viper) searchInPath(in string) (filename string) {
+	v.logger.Debug("searching for config in path", "path", in)
+	for _, ext := range SupportedExts {
+		v.logger.Debug("checking if file exists", "file", filepath.Join(in, v.configName+"."+ext))
+		if b, _ := exists(v.fs, filepath.Join(in, v.configName+"."+ext)); b {
+			v.logger.Debug("found file", "file", filepath.Join(in, v.configName+"."+ext))
+			return filepath.Join(in, v.configName+"."+ext)
+		}
+	}
+
+	if v.configType != "" {
+		if b, _ := exists(v.fs, filepath.Join(in, v.configName)); b {
+			return filepath.Join(in, v.configName)
+		}
+	}
+
+	return ""
+}
+
+// Check if file Exists
+func exists(fs afero.Fs, path string) (bool, error) {
+	stat, err := fs.Stat(path)
+	if err == nil {
+		return !stat.IsDir(), nil
+	}
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	return false, err
+}

viper_go1_16.go

@@ -0,0 +1,32 @@
+//go:build go1.16 && finder
+// +build go1.16,finder
+
+package viper
+
+import (
+	"fmt"
+
+	"github.com/spf13/afero"
+)
+
+// Search all configPaths for any config file.
+// Returns the first path that exists (and is a config file).
+func (v *Viper) findConfigFile() (string, error) {
+	finder := finder{
+		paths:            v.configPaths,
+		fileNames:        []string{v.configName},
+		extensions:       SupportedExts,
+		withoutExtension: v.configType != "",
+	}
+
+	file, err := finder.Find(afero.NewIOFS(v.fs))
+	if err != nil {
+		return "", err
+	}
+
+	if file == "" {
+		return "", ConfigFileNotFoundError{v.configName, fmt.Sprintf("%s", v.configPaths)}
+	}
+
+	return file, nil
+}

viper_test.go

@@ -9,7 +9,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"io"
-	"io/ioutil"
+	"io/ioutil" //nolint:staticcheck
 	"os"
 	"os/exec"
 	"path"
@@ -33,21 +33,21 @@ import (
 	"github.com/spf13/viper/internal/testutil"
 )
 
-var yamlExample = []byte(`Hacker: true
-name: steve
-hobbies:
-- skateboarding
-- snowboarding
-- go
-clothing:
-  jacket: leather
-  trousers: denim
-  pants:
-    size: large
-age: 35
-eyes : brown
-beard: true
-`)
+// var yamlExample = []byte(`Hacker: true
+// name: steve
+// hobbies:
+//     - skateboarding
+//     - snowboarding
+//     - go
+// clothing:
+//     jacket: leather
+//     trousers: denim
+//     pants:
+//         size: large
+// age: 35
+// eyes : brown
+// beard: true
+// `)
 
 var yamlExampleWithExtras = []byte(`Existing: true
 Bogus: true
@@ -263,13 +263,13 @@ func initDirs(t *testing.T) (string, string, func()) {
 	require.Nil(t, err)
 
 	for _, dir := range testDirs {
-		err = os.Mkdir(dir, 0750)
+		err = os.Mkdir(dir, 0o750)
 		assert.Nil(t, err)
 
 		err = ioutil.WriteFile(
 			path.Join(dir, config+".toml"),
 			[]byte("key = \"value is "+dir+"\"\n"),
-			0640)
+			0o640)
 		assert.Nil(t, err)
 	}
 
@@ -301,65 +301,192 @@ func (s *stringValue) String() string {
 	return string(*s)
 }
 
-func TestBasics(t *testing.T) {
-	SetConfigFile("/tmp/config.yaml")
-	filename, err := v.getConfigFile()
-	assert.Equal(t, "/tmp/config.yaml", filename)
-	assert.NoError(t, err)
+func TestGetConfigFile(t *testing.T) {
+	t.Run("config file set", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/etc/viper"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/etc/viper/config.yaml"))
+		require.NoError(t, err)
+
+		v := New()
+
+		v.SetFs(fs)
+		v.AddConfigPath("/etc/viper")
+		v.SetConfigFile(testutil.AbsFilePath(t, "/etc/viper/config.yaml"))
+
+		filename, err := v.getConfigFile()
+		assert.Equal(t, testutil.AbsFilePath(t, "/etc/viper/config.yaml"), filename)
+		assert.NoError(t, err)
+	})
+
+	t.Run("find file", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/etc/viper"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/etc/viper/config.yaml"))
+		require.NoError(t, err)
+
+		v := New()
+
+		v.SetFs(fs)
+		v.AddConfigPath("/etc/viper")
+
+		filename, err := v.getConfigFile()
+		assert.Equal(t, testutil.AbsFilePath(t, "/etc/viper/config.yaml"), filename)
+		assert.NoError(t, err)
+	})
+
+	t.Run("find files only", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/etc/config"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/etc/config/config.yaml"))
+		require.NoError(t, err)
+
+		v := New()
+
+		v.SetFs(fs)
+		v.AddConfigPath("/etc")
+		v.AddConfigPath("/etc/config")
+
+		filename, err := v.getConfigFile()
+		assert.Equal(t, testutil.AbsFilePath(t, "/etc/config/config.yaml"), filename)
+		assert.NoError(t, err)
+	})
+
+	t.Run("precedence", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/home/viper"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/home/viper/config.zml"))
+		require.NoError(t, err)
+
+		err = fs.Mkdir(testutil.AbsFilePath(t, "/etc/viper"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/etc/viper/config.bml"))
+		require.NoError(t, err)
+
+		err = fs.Mkdir(testutil.AbsFilePath(t, "/var/viper"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/var/viper/config.yaml"))
+		require.NoError(t, err)
+
+		v := New()
+
+		v.SetFs(fs)
+		v.AddConfigPath("/home/viper")
+		v.AddConfigPath("/etc/viper")
+		v.AddConfigPath("/var/viper")
+
+		filename, err := v.getConfigFile()
+		assert.Equal(t, testutil.AbsFilePath(t, "/var/viper/config.yaml"), filename)
+		assert.NoError(t, err)
+	})
+
+	t.Run("without extension", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/etc/viper"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/etc/viper/.dotfilenoext"))
+		require.NoError(t, err)
+
+		v := New()
+
+		v.SetFs(fs)
+		v.AddConfigPath("/etc/viper")
+		v.SetConfigName(".dotfilenoext")
+		v.SetConfigType("yaml")
+
+		filename, err := v.getConfigFile()
+		assert.Equal(t, testutil.AbsFilePath(t, "/etc/viper/.dotfilenoext"), filename)
+		assert.NoError(t, err)
+	})
+
+	t.Run("without extension and config type", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/etc/viper"), 0o777)
+		require.NoError(t, err)
+
+		_, err = fs.Create(testutil.AbsFilePath(t, "/etc/viper/.dotfilenoext"))
+		require.NoError(t, err)
+
+		v := New()
+
+		v.SetFs(fs)
+		v.AddConfigPath("/etc/viper")
+		v.SetConfigName(".dotfilenoext")
+
+		_, err = v.getConfigFile()
+		// unless config type is set, files without extension
+		// are not considered
+		assert.Error(t, err)
+	})
 }
 
-func TestSearchInPath_WithoutConfigTypeSet(t *testing.T) {
-	filename := ".dotfilenoext"
-	path := "/tmp"
-	file := filepath.Join(path, filename)
-	SetConfigName(filename)
-	AddConfigPath(path)
-	_, createErr := v.fs.Create(file)
-	defer func() {
-		_ = v.fs.Remove(file)
-	}()
-	assert.NoError(t, createErr)
-	_, err := v.getConfigFile()
-	// unless config type is set, files without extension
-	// are not considered
-	assert.Error(t, err)
-}
+func TestReadInConfig(t *testing.T) {
+	t.Run("config file set", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
 
-func TestSearchInPath(t *testing.T) {
-	filename := ".dotfilenoext"
-	path := "/tmp"
-	file := filepath.Join(path, filename)
-	SetConfigName(filename)
-	SetConfigType("yaml")
-	AddConfigPath(path)
-	_, createErr := v.fs.Create(file)
-	defer func() {
-		_ = v.fs.Remove(file)
-	}()
-	assert.NoError(t, createErr)
-	filename, err := v.getConfigFile()
-	assert.Equal(t, file, filename)
-	assert.NoError(t, err)
-}
+		err := fs.Mkdir("/etc/viper", 0o777)
+		require.NoError(t, err)
 
-func TestSearchInPath_FilesOnly(t *testing.T) {
-	fs := afero.NewMemMapFs()
+		file, err := fs.Create(testutil.AbsFilePath(t, "/etc/viper/config.yaml"))
+		require.NoError(t, err)
 
-	err := fs.Mkdir("/tmp/config", 0777)
-	require.NoError(t, err)
+		_, err = file.Write([]byte(`key: value`))
+		require.NoError(t, err)
 
-	_, err = fs.Create("/tmp/config/config.yaml")
-	require.NoError(t, err)
+		file.Close()
 
-	v := New()
+		v := New()
 
-	v.SetFs(fs)
-	v.AddConfigPath("/tmp")
-	v.AddConfigPath("/tmp/config")
+		v.SetFs(fs)
+		v.SetConfigFile(testutil.AbsFilePath(t, "/etc/viper/config.yaml"))
 
-	filename, err := v.getConfigFile()
-	assert.Equal(t, "/tmp/config/config.yaml", filename)
-	assert.NoError(t, err)
+		err = v.ReadInConfig()
+		require.NoError(t, err)
+
+		assert.Equal(t, "value", v.Get("key"))
+	})
+
+	t.Run("find file", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/etc/viper"), 0o777)
+		require.NoError(t, err)
+
+		file, err := fs.Create(testutil.AbsFilePath(t, "/etc/viper/config.yaml"))
+		require.NoError(t, err)
+
+		_, err = file.Write([]byte(`key: value`))
+		require.NoError(t, err)
+
+		file.Close()
+
+		v := New()
+
+		v.SetFs(fs)
+		v.AddConfigPath("/etc/viper")
+
+		err = v.ReadInConfig()
+		require.NoError(t, err)
+
+		assert.Equal(t, "value", v.Get("key"))
+	})
 }
 
 func TestDefault(t *testing.T) {
@@ -382,7 +509,9 @@ func TestUnmarshaling(t *testing.T) {
 
 	unmarshalReader(r, v.config)
 	assert.True(t, InConfig("name"))
+	assert.True(t, InConfig("clothing.jacket"))
 	assert.False(t, InConfig("state"))
+	assert.False(t, InConfig("clothing.hat"))
 	assert.Equal(t, "steve", Get("name"))
 	assert.Equal(t, []interface{}{"skateboarding", "snowboarding", "go"}, Get("hobbies"))
 	assert.Equal(t, map[string]interface{}{"jacket": "leather", "trousers": "denim", "pants": map[string]interface{}{"size": "large"}}, Get("clothing"))
@@ -869,7 +998,7 @@ func TestBindPFlags(t *testing.T) {
 	}
 }
 
-// nolint: dupl
+//nolint:dupl
 func TestBindPFlagsStringSlice(t *testing.T) {
 	tests := []struct {
 		Expected []string
@@ -917,7 +1046,7 @@ func TestBindPFlagsStringSlice(t *testing.T) {
 	}
 }
 
-// nolint: dupl
+//nolint:dupl
 func TestBindPFlagsStringArray(t *testing.T) {
 	tests := []struct {
 		Expected []string
@@ -965,7 +1094,7 @@ func TestBindPFlagsStringArray(t *testing.T) {
 	}
 }
 
-// nolint: dupl
+//nolint:dupl
 func TestBindPFlagsIntSlice(t *testing.T) {
 	tests := []struct {
 		Expected []int
@@ -1239,7 +1368,9 @@ func TestReadBufConfig(t *testing.T) {
 	t.Log(v.AllKeys())
 
 	assert.True(t, v.InConfig("name"))
+	assert.True(t, v.InConfig("clothing.jacket"))
 	assert.False(t, v.InConfig("state"))
+	assert.False(t, v.InConfig("clothing.hat"))
 	assert.Equal(t, "steve", v.Get("name"))
 	assert.Equal(t, []interface{}{"skateboarding", "snowboarding", "go"}, v.Get("hobbies"))
 	assert.Equal(t, map[string]interface{}{"jacket": "leather", "trousers": "denim", "pants": map[string]interface{}{"size": "large"}}, v.Get("clothing"))
@@ -1427,21 +1558,21 @@ p_ppu = 0.55
 p_batters.batter.type = Regular
 `)
 
-var yamlWriteExpected = []byte(`age: 35
-beard: true
-clothing:
-  jacket: leather
-  pants:
-    size: large
-  trousers: denim
-eyes: brown
-hacker: true
-hobbies:
-- skateboarding
-- snowboarding
-- go
-name: steve
-`)
+// var yamlWriteExpected = []byte(`age: 35
+// beard: true
+// clothing:
+//     jacket: leather
+//     pants:
+//         size: large
+//     trousers: denim
+// eyes: brown
+// hacker: true
+// hobbies:
+//     - skateboarding
+//     - snowboarding
+//     - go
+// name: steve
+// `)
 
 func TestWriteConfig(t *testing.T) {
 	fs := afero.NewMemMapFs()
@@ -1685,7 +1816,7 @@ func TestSafeWriteConfig(t *testing.T) {
 	v.SetConfigType("yaml")
 	require.NoError(t, v.ReadConfig(bytes.NewBuffer(yamlExample)))
 	require.NoError(t, v.SafeWriteConfig())
-	read, err := afero.ReadFile(fs, "/test/c.yaml")
+	read, err := afero.ReadFile(fs, testutil.AbsFilePath(t, "/test/c.yaml"))
 	require.NoError(t, err)
 	assert.Equal(t, yamlWriteExpected, read)
 }
@@ -1702,7 +1833,7 @@ func TestSafeWriteConfigWithMissingConfigPath(t *testing.T) {
 func TestSafeWriteConfigWithExistingFile(t *testing.T) {
 	v := New()
 	fs := afero.NewMemMapFs()
-	fs.Create("/test/c.yaml")
+	fs.Create(testutil.AbsFilePath(t, "/test/c.yaml"))
 	v.SetFs(fs)
 	v.AddConfigPath("/test")
 	v.SetConfigName("c")
@@ -1738,6 +1869,23 @@ func TestSafeWriteConfigAsWithExistingFile(t *testing.T) {
 	assert.True(t, ok, "Expected ConfigFileAlreadyExistsError")
 }
 
+func TestWriteHiddenFile(t *testing.T) {
+	v := New()
+	fs := afero.NewMemMapFs()
+	fs.Create(testutil.AbsFilePath(t, "/test/.config"))
+	v.SetFs(fs)
+
+	v.SetConfigName(".config")
+	v.SetConfigType("yaml")
+	v.AddConfigPath("/test")
+
+	err := v.ReadInConfig()
+	require.NoError(t, err)
+
+	err = v.WriteConfig()
+	require.NoError(t, err)
+}
+
 var yamlMergeExampleTgt = []byte(`
 hello:
     pop: 37890
@@ -1764,6 +1912,24 @@ hello:
 fu: bar
 `)
 
+var jsonMergeExampleTgt = []byte(`
+{
+	"hello": {
+		"foo": null,
+		"pop": 123456
+	}
+}
+`)
+
+var jsonMergeExampleSrc = []byte(`
+{
+	"hello": {
+		"foo": "foo str",
+		"pop": "pop str"
+	}
+}
+`)
+
 func TestMergeConfig(t *testing.T) {
 	v := New()
 	v.SetConfigType("yml")
@@ -1787,6 +1953,10 @@ func TestMergeConfig(t *testing.T) {
 		t.Fatalf("uint pop != 37890, = %d", pop)
 	}
 
+	if pop := v.GetUint16("hello.pop"); pop != uint16(37890) {
+		t.Fatalf("uint pop != 37890, = %d", pop)
+	}
+
 	if pop := v.GetUint32("hello.pop"); pop != 37890 {
 		t.Fatalf("uint32 pop != 37890, = %d", pop)
 	}
@@ -1836,6 +2006,26 @@ func TestMergeConfig(t *testing.T) {
 	}
 }
 
+func TestMergeConfigOverrideType(t *testing.T) {
+	v := New()
+	v.SetConfigType("json")
+	if err := v.ReadConfig(bytes.NewBuffer(jsonMergeExampleTgt)); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := v.MergeConfig(bytes.NewBuffer(jsonMergeExampleSrc)); err != nil {
+		t.Fatal(err)
+	}
+
+	if pop := v.GetString("hello.pop"); pop != "pop str" {
+		t.Fatalf("pop != \"pop str\", = %s", pop)
+	}
+
+	if foo := v.GetString("hello.foo"); foo != "foo str" {
+		t.Fatalf("foo != \"foo str\", = %s", foo)
+	}
+}
+
 func TestMergeConfigNoMerge(t *testing.T) {
 	v := New()
 	v.SetConfigType("yml")
@@ -2142,7 +2332,7 @@ func newViperWithConfigFile(t *testing.T) (*Viper, string, func()) {
 	watchDir, err := ioutil.TempDir("", "")
 	require.Nil(t, err)
 	configFile := path.Join(watchDir, "config.yaml")
-	err = ioutil.WriteFile(configFile, []byte("foo: bar\n"), 0640)
+	err = ioutil.WriteFile(configFile, []byte("foo: bar\n"), 0o640)
 	require.Nil(t, err)
 	cleanup := func() {
 		os.RemoveAll(watchDir)
@@ -2159,11 +2349,11 @@ func newViperWithSymlinkedConfigFile(t *testing.T) (*Viper, string, string, func
 	watchDir, err := ioutil.TempDir("", "")
 	require.Nil(t, err)
 	dataDir1 := path.Join(watchDir, "data1")
-	err = os.Mkdir(dataDir1, 0777)
+	err = os.Mkdir(dataDir1, 0o777)
 	require.Nil(t, err)
 	realConfigFile := path.Join(dataDir1, "config.yaml")
 	t.Logf("Real config file location: %s\n", realConfigFile)
-	err = ioutil.WriteFile(realConfigFile, []byte("foo: bar\n"), 0640)
+	err = ioutil.WriteFile(realConfigFile, []byte("foo: bar\n"), 0o640)
 	require.Nil(t, err)
 	cleanup := func() {
 		os.RemoveAll(watchDir)
@@ -2198,13 +2388,16 @@ func TestWatchFile(t *testing.T) {
 		t.Logf("test config file: %s\n", configFile)
 		wg := sync.WaitGroup{}
 		wg.Add(1)
+		var wgDoneOnce sync.Once // OnConfigChange is called twice on Windows
 		v.OnConfigChange(func(in fsnotify.Event) {
 			t.Logf("config file changed")
-			wg.Done()
+			wgDoneOnce.Do(func() {
+				wg.Done()
+			})
 		})
 		v.WatchConfig()
 		// when overwriting the file and waiting for the custom change notification handler to be triggered
-		err = ioutil.WriteFile(configFile, []byte("foo: baz\n"), 0640)
+		err = ioutil.WriteFile(configFile, []byte("foo: baz\n"), 0o640)
 		wg.Wait()
 		// then the config value should have changed
 		require.Nil(t, err)
@@ -2227,10 +2420,10 @@ func TestWatchFile(t *testing.T) {
 		wg.Add(1)
 		// when link to another `config.yaml` file
 		dataDir2 := path.Join(watchDir, "data2")
-		err := os.Mkdir(dataDir2, 0777)
+		err := os.Mkdir(dataDir2, 0o777)
 		require.Nil(t, err)
 		configFile2 := path.Join(dataDir2, "config.yaml")
-		err = ioutil.WriteFile(configFile2, []byte("foo: baz\n"), 0640)
+		err = ioutil.WriteFile(configFile2, []byte("foo: baz\n"), 0o640)
 		require.Nil(t, err)
 		// change the symlink using the `ln -sfn` command
 		err = exec.Command("ln", "-sfn", dataDir2, path.Join(watchDir, "data")).Run()
@@ -2259,25 +2452,25 @@ func TestUnmarshal_DotSeparatorBackwardCompatibility(t *testing.T) {
 	assert.Equal(t, "cobra_flag", config.Foo.Bar)
 }
 
-var yamlExampleWithDot = []byte(`Hacker: true
-name: steve
-hobbies:
-  - skateboarding
-  - snowboarding
-  - go
-clothing:
-  jacket: leather
-  trousers: denim
-  pants:
-    size: large
-age: 35
-eyes : brown
-beard: true
-emails:
-  steve@hacker.com:
-    created: 01/02/03
-    active: true
-`)
+// var yamlExampleWithDot = []byte(`Hacker: true
+// name: steve
+// hobbies:
+//     - skateboarding
+//     - snowboarding
+//     - go
+// clothing:
+//     jacket: leather
+//     trousers: denim
+//     pants:
+//         size: large
+// age: 35
+// eyes : brown
+// beard: true
+// emails:
+//     steve@hacker.com:
+//         created: 01/02/03
+//         active: true
+// `)
 
 func TestKeyDelimiter(t *testing.T) {
 	v := NewWithOptions(KeyDelimiter("::"))
@@ -2327,7 +2520,10 @@ func TestKeyDelimiter(t *testing.T) {
 }
 
 var yamlDeepNestedSlices = []byte(`TV:
-- title: "The expanse"
+- title: "The Expanse"
+  title_i18n:
+    USA: "The Expanse"
+    Japan: "エクスパンス -巨獣めざめる-"
   seasons:
   - first_released: "December 14, 2015"
     episodes:
@@ -2357,11 +2553,15 @@ func TestSliceIndexAccess(t *testing.T) {
 	err := v.unmarshalReader(r, v.config)
 	require.NoError(t, err)
 
-	assert.Equal(t, "The expanse", v.GetString("tv.0.title"))
+	assert.Equal(t, "The Expanse", v.GetString("tv.0.title"))
 	assert.Equal(t, "February 1, 2017", v.GetString("tv.0.seasons.1.first_released"))
 	assert.Equal(t, "Static", v.GetString("tv.0.seasons.1.episodes.2.title"))
 	assert.Equal(t, "December 15, 2015", v.GetString("tv.0.seasons.0.episodes.1.air_date"))
 
+	// Test nested keys with capital letters
+	assert.Equal(t, "The Expanse", v.GetString("tv.0.title_i18n.USA"))
+	assert.Equal(t, "エクスパンス -巨獣めざめる-", v.GetString("tv.0.title_i18n.Japan"))
+
 	// Test for index out of bounds
 	assert.Equal(t, "", v.GetString("tv.0.seasons.2.first_released"))
 
@@ -2405,3 +2605,10 @@ func BenchmarkGetBoolFromMap(b *testing.B) {
 		}
 	}
 }
+
+// Skip some tests on Windows that kept failing when Windows was added to the CI as a target.
+func skipWindows(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Skip test on Windows")
+	}
+}

viper_yaml_test.go

@@ -0,0 +1,53 @@
+package viper
+
+var yamlExample = []byte(`Hacker: true
+name: steve
+hobbies:
+    - skateboarding
+    - snowboarding
+    - go
+clothing:
+    jacket: leather
+    trousers: denim
+    pants:
+        size: large
+age: 35
+eyes : brown
+beard: true
+`)
+
+var yamlWriteExpected = []byte(`age: 35
+beard: true
+clothing:
+    jacket: leather
+    pants:
+        size: large
+    trousers: denim
+eyes: brown
+hacker: true
+hobbies:
+    - skateboarding
+    - snowboarding
+    - go
+name: steve
+`)
+
+var yamlExampleWithDot = []byte(`Hacker: true
+name: steve
+hobbies:
+    - skateboarding
+    - snowboarding
+    - go
+clothing:
+    jacket: leather
+    trousers: denim
+    pants:
+        size: large
+age: 35
+eyes : brown
+beard: true
+emails:
+    steve@hacker.com:
+        created: 01/02/03
+        active: true
+`)

watch.go

@@ -1,4 +1,5 @@
-// +build !js
+//go:build darwin || dragonfly || freebsd || openbsd || linux || netbsd || solaris || windows
+// +build darwin dragonfly freebsd openbsd linux netbsd solaris windows
 
 package viper
 

watch_unsupported.go

@@ -1,13 +1,19 @@
-// +build js,wasm
+//go:build appengine || (!darwin && !dragonfly && !freebsd && !openbsd && !linux && !netbsd && !solaris && !windows)
+// +build appengine !darwin,!dragonfly,!freebsd,!openbsd,!linux,!netbsd,!solaris,!windows
 
 package viper
 
 import (
-	"errors"
+	"fmt"
+	"runtime"
 
 	"github.com/fsnotify/fsnotify"
 )
 
+func newWatcher() (*watcher, error) {
+	return &watcher{}, fmt.Errorf("fsnotify not supported on %s", runtime.GOOS)
+}
+
 type watcher struct {
 	Events chan fsnotify.Event
 	Errors chan error
@@ -24,7 +30,3 @@ func (*watcher) Add(name string) error {
 func (*watcher) Remove(name string) error {
 	return nil
 }
-
-func newWatcher() (*watcher, error) {
-	return &watcher{}, errors.New("fsnotify is not supported on WASM")
-}