build(deps): bump actions/checkout from 4.1.2 to 4.1.3

Bumps [actions/checkout](https://github.com/actions/checkout) from 4.1.2 to 4.1.3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/9bb56186c3b09b4f86b1c65136769dd318469633...1d96c772d19495a3b5c517cd2bc0cb401ea0529f)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

.editorconfig

@@ -11,5 +11,8 @@ trim_trailing_whitespace = true
 [*.go]
 indent_style = tab
 
-[{Makefile, *.mk}]
+[{Makefile,*.mk}]
 indent_style = tab
+
+[*.nix]
+indent_size = 2

.envrc

@@ -0,0 +1,4 @@
+if ! has nix_direnv_version || ! nix_direnv_version 2.3.0; then
+  source_url "https://raw.githubusercontent.com/nix-community/nix-direnv/2.3.0/direnvrc" "sha256-Dmd+j63L84wuzgyjITIfSxSD57Tx7v51DMxVZOsiUD8="
+fi
+use flake . --impure

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -19,6 +19,8 @@ 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: Viper Version

.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 +1,30 @@
+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@132879b972cb7f2ac593006455875098e73cc7f2 # v5.4.0
+        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
+            release-note/misc

.github/workflows/ci.yaml

@@ -0,0 +1,115 @@
+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: Checkout repository
+        uses: actions/checkout@1d96c772d19495a3b5c517cd2bc0cb401ea0529f # v4.1.3
+
+      - name: Set up Go
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
+        with:
+          go-version: "1.22"
+
+      - 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: ["1.20", "1.21", "1.22"]
+        tags: ["", "finder", "viper_bind_struct"]
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@1d96c772d19495a3b5c517cd2bc0cb401ea0529f # v4.1.3
+
+      - name: Set up Go
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
+        with:
+          go-version: ${{ matrix.go }}
+
+      - name: Test
+        run: go test -race -v -tags '${{ matrix.tags }}' -shuffle=on ./...
+        if: runner.os != 'Windows'
+
+      - name: Test (without race detector)
+        run: go test -v -tags '${{ matrix.tags }}' -shuffle=on ./...
+        if: runner.os == 'Windows'
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@1d96c772d19495a3b5c517cd2bc0cb401ea0529f # v4.1.3
+
+      - name: Set up Go
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
+        with:
+          go-version: "1.22"
+
+      - name: Lint
+        uses: golangci/golangci-lint-action@3cfe3a4abbb849e10058ce4af15d205b6da42804 # v4.0.0
+        with:
+          version: v1.56.1
+
+  dev:
+    name: Developer environment
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@1d96c772d19495a3b5c517cd2bc0cb401ea0529f # v4.1.3
+
+      - name: Set up Nix
+        uses: cachix/install-nix-action@8887e596b4ee1134dae06b98d573bd674693f47c # v26
+        with:
+          extra_nix_config: |
+            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+
+      - name: Check
+        run: nix flake check --impure
+
+      - name: Dev shell
+        run: nix develop --impure
+
+  dependency-review:
+    name: Dependency review
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@1d96c772d19495a3b5c517cd2bc0cb401ea0529f # v4.1.3
+
+      - name: Dependency Review
+        uses: actions/dependency-review-action@5bbc3ba658137598168acb2ab73b21c432dd411b # v4.2.5

.github/workflows/ci.yml

@@ -1,53 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches:
-      - master
-  pull_request:
-
-jobs:
-  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: ['1.14', '1.15', '1.16', '1.17']
-    env:
-      GOFLAGS: -mod=readonly
-
-    steps:
-      - name: Set up Go
-        uses: actions/setup-go@v2
-        with:
-          go-version: ${{ matrix.go }}
-
-      - name: Checkout code
-        uses: actions/checkout@v2
-
-      - name: Test
-        run: go test -race -v ./...
-
-  lint:
-    name: Lint
-    runs-on: ubuntu-latest
-    env:
-      GOFLAGS: -mod=readonly
-
-    steps:
-      - name: Set up Go
-        uses: actions/setup-go@v2
-        with:
-          go-version: 1.17
-
-      - name: Checkout code
-        uses: actions/checkout@v2
-
-      - name: Lint
-        uses: golangci/golangci-lint-action@v2
-        with:
-          version: v1.43.0

.github/workflows/codeql-analysis.yaml

@@ -39,11 +39,11 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@1d96c772d19495a3b5c517cd2bc0cb401ea0529f # v4.1.3
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v1
+      uses: github/codeql-action/init@c7f9125735019aa87cfc361530512d50ea439c71 # v3.25.1
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -54,7 +54,7 @@ jobs:
     # 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@v1
+      uses: github/codeql-action/autobuild@c7f9125735019aa87cfc361530512d50ea439c71 # v3.25.1
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 https://git.io/JvXDl
@@ -68,5 +68,5 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v1
+      uses: github/codeql-action/analyze@c7f9125735019aa87cfc361530512d50ea439c71 # v3.25.1
 

.github/workflows/feedback_issue.yaml

@@ -6,7 +6,7 @@ jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/github-script@v5
+      - uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
         with:
           github-token: ${{secrets.GITHUB_TOKEN}}
           script: |

.github/workflows/feedback_pull_request.yaml

@@ -6,7 +6,7 @@ jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/github-script@v5
+      - uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
         with:
           github-token: ${{secrets.GITHUB_TOKEN}}
           script: |

.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: '1.17'
-
-      - name: Checkout code
-        uses: actions/checkout@v2
-
-      - name: Ensure Viper compiles for WASM
-        run: GOOS=js GOARCH=wasm go build .

.gitignore

@@ -1,4 +1,7 @@
+/.devenv/
+/.direnv/
 /.idea/
+/.pre-commit-config.yaml
 /bin/
 /build/
 /var/

.golangci.yaml

@@ -3,7 +3,20 @@ run:
 
 linters-settings:
     gci:
-        local-prefixes: github.com/spf13/viper
+        sections:
+            - standard
+            - default
+            - prefix(github.com/spf13/viper)
+    gocritic:
+        # Enable multiple checks by tags. See "Tags" section in https://github.com/go-critic/go-critic#usage.
+        enabled-tags:
+            - diagnostic
+            - experimental
+            - opinionated
+            - style
+        disabled-checks:
+            - importShadow
+            - unnamedResult
     golint:
         min-confidence: 0
     goimports:
@@ -13,13 +26,14 @@ linters:
     disable-all: true
     enable:
         - bodyclose
-        - deadcode
         - dogsled
         - dupl
         - durationcheck
         - exhaustive
         - exportloopref
         - gci
+        - gocritic
+        - godot
         - gofmt
         - gofumpt
         - goimports
@@ -40,14 +54,12 @@ linters:
         - rowserrcheck
         - sqlclosecheck
         - staticcheck
-        - structcheck
         - stylecheck
         - tparallel
         - typecheck
         - unconvert
         - unparam
         - unused
-        - varcheck
         - wastedassign
         - whitespace
 
@@ -62,9 +74,7 @@ linters:
         # - gochecknoinits
         # - gocognit
         # - goconst
-        # - gocritic
         # - gocyclo
-        # - godot
         # - gosec
         # - gosimple
         # - ifshort
@@ -80,6 +90,11 @@ linters:
         # - goheader
         # - gomodguard
 
+        # deprecated
+        # - deadcode
+        # - structcheck
+        # - varcheck
+
         # don't enable:
         # - asciicheck
         # - funlen

.yamlignore

@@ -0,0 +1,2 @@
+# TODO: FIXME
+/.github/

.yamllint.yaml

@@ -0,0 +1,6 @@
+ignore-from-file: [.gitignore, .yamlignore]
+
+extends: default
+
+rules:
+  line-length: disable

Makefile

@@ -15,8 +15,8 @@ TEST_FORMAT = short-verbose
 endif
 
 # Dependency versions
-GOTESTSUM_VERSION = 1.7.0
-GOLANGCI_VERSION = 1.43.0
+GOTESTSUM_VERSION = 1.9.0
+GOLANGCI_VERSION = 1.53.3
 
 # Add the ability to override some variables
 # Use with care
@@ -29,11 +29,6 @@ clear: ## Clear the working area and the project
 .PHONY: check
 check: test lint ## Run tests and linters
 
-bin/gotestsum: bin/gotestsum-${GOTESTSUM_VERSION}
-	@ln -sf gotestsum-${GOTESTSUM_VERSION} bin/gotestsum
-bin/gotestsum-${GOTESTSUM_VERSION}:
-	@mkdir -p bin
-	curl -L https://github.com/gotestyourself/gotestsum/releases/download/v${GOTESTSUM_VERSION}/gotestsum_${GOTESTSUM_VERSION}_${OS}_amd64.tar.gz | tar -zOxf - gotestsum > ./bin/gotestsum-${GOTESTSUM_VERSION} && chmod +x ./bin/gotestsum-${GOTESTSUM_VERSION}
 
 TEST_PKGS ?= ./...
 .PHONY: test
@@ -44,20 +39,36 @@ test: bin/gotestsum ## Run tests
 	@mkdir -p ${BUILD_DIR}
 	bin/gotestsum --no-summary=skipped --junitfile ${BUILD_DIR}/coverage.xml --format ${TEST_FORMAT} -- -race -coverprofile=${BUILD_DIR}/coverage.txt -covermode=atomic $(filter-out -v,${GOARGS}) $(if ${TEST_PKGS},${TEST_PKGS},./...)
 
-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}
-	@mv bin/golangci-lint "$@"
-
 .PHONY: lint
-lint: bin/golangci-lint ## Run linter
-	bin/golangci-lint run
+lint: lint-go lint-yaml
+lint: ## Run linters
 
-.PHONY: fix
-fix: bin/golangci-lint ## Fix lint violations
-	bin/golangci-lint run --fix
+.PHONY: lint-go
+lint-go:
+	golangci-lint run $(if ${CI},--out-format github-actions,)
+
+.PHONY: lint-yaml
+lint-yaml:
+	yamllint $(if ${CI},-f github,) --no-warnings .
+
+.PHONY: fmt
+fmt: ## Format code
+	golangci-lint run --fix
+
+deps: bin/golangci-lint bin/gotestsum yamllint
+deps: ## Install dependencies
+
+bin/gotestsum:
+	@mkdir -p bin
+	curl -L https://github.com/gotestyourself/gotestsum/releases/download/v${GOTESTSUM_VERSION}/gotestsum_${GOTESTSUM_VERSION}_${OS}_amd64.tar.gz | tar -zOxf - gotestsum > ./bin/gotestsum && chmod +x ./bin/gotestsum
+
+bin/golangci-lint:
+	@mkdir -p bin
+	curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | bash -s -- v${GOLANGCI_VERSION}
+
+.PHONY: yamllint
+yamllint:
+	pip3 install --user yamllint
 
 # Add custom targets here
 -include custom.mk

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=1.20-61CFDD.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!**
@@ -27,6 +27,10 @@ Many Go projects are built using Viper including:
 * [doctl](https://github.com/digitalocean/doctl)
 * [Clairctl](https://github.com/jgsqware/clairctl)
 * [Mercure](https://mercure.rocks)
+* [Meshery](https://github.com/meshery/meshery)
+* [Bearer](https://github.com/bearer/bearer)
+* [Coder](https://github.com/coder/coder)
+* [Vitess](https://vitess.io/)
 
 
 ## Install
@@ -35,13 +39,13 @@ Many Go projects are built using Viper including:
 go get github.com/spf13/viper
 ```
 
-**Note:** Viper uses [Go Modules](https://github.com/golang/go/wiki/Modules) to manage dependencies.
+**Note:** Viper uses [Go Modules](https://go.dev/wiki/Modules) to manage dependencies.
 
 
 ## 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 +123,7 @@ 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))
 }
 ```
 
@@ -137,7 +141,7 @@ if err := viper.ReadInConfig(); err != nil {
 // Config file found and successfully parsed
 ```
 
-*NOTE [since 1.6]:* You can also have a file without an extension and specify the format programmaticaly. For those configuration files that lie in the home of the user without any extension like `.bashrc`
+*NOTE [since 1.6]:* You can also have a file without an extension and specify the format programmatically. For those configuration files that lie in the home of the user without any extension like `.bashrc`
 
 ### Writing Config Files
 
@@ -218,6 +222,7 @@ These could be from a command line flag, or from your own application logic.
 ```go
 viper.Set("Verbose", true)
 viper.Set("LogFile", LogFile)
+viper.Set("host.port", 5899)   // set subset
 ```
 
 ### Registering and Using Aliases
@@ -413,6 +418,8 @@ in a Key/Value store such as etcd or Consul.  These values take precedence over
 default values, but are overridden by configuration values retrieved from disk,
 flags, or environment variables.
 
+Viper supports multiple hosts. To use, pass a list of endpoints separated by `;`. For example `http://127.0.0.1:4001;http://127.0.0.1:4002`.
+
 Viper uses [crypt](https://github.com/bketelsen/crypt) to retrieve
 configuration from the K/V store, which means that you can store your
 configuration values encrypted and have them automatically decrypted if you have
@@ -447,6 +454,13 @@ 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:
@@ -477,6 +491,15 @@ err := viper.ReadRemoteConfig()
 
 Of course, you're allowed to use `SecureRemoteProvider` also
 
+
+#### NATS
+
+```go
+viper.AddRemoteProvider("nats", "nats://127.0.0.1:4222", "myapp.config")
+viper.SetConfigType("json")
+err := viper.ReadRemoteConfig()
+```
+
 ### Remote Key/Value Store Example - Encrypted
 
 ```go
@@ -524,24 +547,27 @@ go func(){
 In Viper, there are a few ways to get a value depending on the value’s type.
 The following functions and methods exist:
 
- * `Get(key string) : interface{}`
+ * `Get(key string) : any`
  * `GetBool(key string) : bool`
  * `GetFloat64(key string) : float64`
  * `GetInt(key string) : int`
  * `GetIntSlice(key string) : []int`
  * `GetString(key string) : string`
- * `GetStringMap(key string) : map[string]interface{}`
+ * `GetStringMap(key string) : map[string]any`
  * `GetStringMapString(key string) : map[string]string`
  * `GetStringSlice(key string) : []string`
  * `GetTime(key string) : time.Time`
  * `GetDuration(key string) : time.Duration`
  * `IsSet(key string) : bool`
- * `AllSettings() : map[string]interface{}`
+ * `AllSettings() : map[string]any`
 
 One important thing to recognize is that each Get function will return a zero
 value if it’s not found. To check if a given key exists, the `IsSet()` method
 has been provided.
 
+The zero value will also be returned if the value is set, but fails to parse
+as the requested type.
+
 Example:
 ```go
 viper.GetString("logfile") // case-insensitive Setting & Getting
@@ -594,7 +620,7 @@ configuration level.
 
 Viper can access array indices by using numbers in the path. For example:
 
-```json
+```jsonc
 {
     "host": {
         "address": "localhost",
@@ -622,7 +648,7 @@ 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": {
@@ -699,8 +725,8 @@ etc.
 
 There are two methods to do this:
 
- * `Unmarshal(rawVal interface{}) : error`
- * `UnmarshalKey(key string, rawVal interface{}) : error`
+ * `Unmarshal(rawVal any) : error`
+ * `UnmarshalKey(key string, rawVal any) : error`
 
 Example:
 
@@ -725,9 +751,9 @@ you have to change the delimiter:
 ```go
 v := viper.NewWithOptions(viper.KeyDelimiter("::"))
 
-v.SetDefault("chart::values", map[string]interface{}{
-	"ingress": map[string]interface{}{
-		"annotations": map[string]interface{}{
+v.SetDefault("chart::values", map[string]any{
+	"ingress": map[string]any{
+		"annotations": map[string]any{
 			"traefik.frontend.rule.type":                 "PathPrefix",
 			"traefik.ingress.kubernetes.io/ssl-redirect": "true",
 		},
@@ -736,7 +762,7 @@ v.SetDefault("chart::values", map[string]interface{}{
 
 type config struct {
 	Chart struct{
-		Values map[string]interface{}
+		Values map[string]any
 	}
 }
 
@@ -872,3 +898,31 @@ No, you will need to synchronize access to the viper yourself (for example by us
 ## Troubleshooting
 
 See [TROUBLESHOOTING.md](TROUBLESHOOTING.md).
+
+## Development
+
+**For an optimal developer experience, it is recommended to install [Nix](https://nixos.org/download.html) and [direnv](https://direnv.net/docs/installation.html).**
+
+_Alternatively, install [Go](https://go.dev/dl/) on your computer then run `make deps` to install the rest of the dependencies._
+
+Run the test suite:
+
+```shell
+make test
+```
+
+Run linters:
+
+```shell
+make lint # pass -j option to run them in parallel
+```
+
+Some linter violations can automatically be fixed:
+
+```shell
+make fmt
+```
+
+## License
+
+The project is licensed under the [MIT License](LICENSE).

TROUBLESHOOTING.md

@@ -15,9 +15,18 @@ cannot find package "github.com/hashicorp/hcl/tree/hcl1" in any of:
 ```
 
 As the error message suggests, Go tries to look up dependencies in `GOPATH` mode (as it's commonly called) from the `GOPATH`.
-Viper opted to use [Go Modules](https://github.com/golang/go/wiki/Modules) to manage its dependencies. While in many cases the two methods are interchangeable, once a dependency releases new (major) versions, `GOPATH` mode is no longer able to decide which version to use, so it'll either use one that's already present or pick a version (usually the `master` branch).
+Viper opted to use [Go Modules](https://go.dev/wiki/Modules) to manage its dependencies. While in many cases the two methods are interchangeable, once a dependency releases new (major) versions, `GOPATH` mode is no longer able to decide which version to use, so it'll either use one that's already present or pick a version (usually the `master` branch).
 
 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.
+Please refer to the [wiki](https://go.dev/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)

file.go

@@ -1,5 +1,4 @@
-//go:build !go1.16 || !finder
-// +build !go1.16 !finder
+//go:build !finder
 
 package viper
 
@@ -44,7 +43,7 @@ func (v *Viper) searchInPath(in string) (filename string) {
 	return ""
 }
 
-// Check if file Exists
+// exists checks if file exists.
 func exists(fs afero.Fs, path string) (bool, error) {
 	stat, err := fs.Stat(path)
 	if err == nil {

file_finder.go

@@ -0,0 +1,38 @@
+//go:build finder
+
+package viper
+
+import (
+	"fmt"
+
+	"github.com/sagikazarmark/locafero"
+)
+
+// Search all configPaths for any config file.
+// Returns the first path that exists (and is a config file).
+func (v *Viper) findConfigFile() (string, error) {
+	var names []string
+
+	if v.configType != "" {
+		names = locafero.NameWithOptionalExtensions(v.configName, SupportedExts...)
+	} else {
+		names = locafero.NameWithExtensions(v.configName, SupportedExts...)
+	}
+
+	finder := locafero.Finder{
+		Paths: v.configPaths,
+		Names: names,
+		Type:  locafero.FileTypeFile,
+	}
+
+	results, err := finder.Find(v.fs)
+	if err != nil {
+		return "", err
+	}
+
+	if len(results) == 0 {
+		return "", ConfigFileNotFoundError{v.configName, fmt.Sprintf("%s", v.configPaths)}
+	}
+
+	return results[0], nil
+}

flags.go

@@ -30,8 +30,8 @@ func (p pflagValueSet) VisitAll(fn func(flag FlagValue)) {
 	})
 }
 
-// pflagValue is a wrapper aroung *pflag.flag
-// that implements FlagValue
+// pflagValue is a wrapper around *pflag.flag
+// that implements FlagValue.
 type pflagValue struct {
 	flag *pflag.Flag
 }

flags_test.go

@@ -5,9 +5,11 @@ import (
 
 	"github.com/spf13/pflag"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestBindFlagValueSet(t *testing.T) {
+	Reset()
 	flagSet := pflag.NewFlagSet("test", pflag.ContinueOnError)
 
 	testValues := map[string]*string{
@@ -29,9 +31,7 @@ func TestBindFlagValueSet(t *testing.T) {
 	flagValueSet := pflagValueSet{flagSet}
 
 	err := BindFlagValues(flagValueSet)
-	if err != nil {
-		t.Fatalf("error binding flag set, %v", err)
-	}
+	require.NoError(t, err, "error binding flag set")
 
 	flagSet.VisitAll(func(flag *pflag.Flag) {
 		flag.Value.Set(mutatedTestValues[flag.Name])
@@ -39,7 +39,7 @@ func TestBindFlagValueSet(t *testing.T) {
 	})
 
 	for name, expected := range mutatedTestValues {
-		assert.Equal(t, Get(name), expected)
+		assert.Equal(t, expected, Get(name))
 	}
 }
 

flake.lock

@@ -0,0 +1,273 @@
+{
+  "nodes": {
+    "devenv": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "nix": "nix",
+        "nixpkgs": "nixpkgs",
+        "pre-commit-hooks": "pre-commit-hooks"
+      },
+      "locked": {
+        "lastModified": 1707817777,
+        "narHash": "sha256-vHyIs1OULQ3/91wD6xOiuayfI71JXALGA5KLnDKAcy0=",
+        "owner": "cachix",
+        "repo": "devenv",
+        "rev": "5a30b9e5ac7c6167e61b1f4193d5130bb9f8defa",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "devenv",
+        "type": "github"
+      }
+    },
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1673956053,
+        "narHash": "sha256-4gtG9iQuiKITOjNQQeQIpoIB6b16fm+504Ch3sNKLd8=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "35bb57c0c8d8b62bbfd284272c928ceb64ddbde9",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "flake-parts": {
+      "inputs": {
+        "nixpkgs-lib": "nixpkgs-lib"
+      },
+      "locked": {
+        "lastModified": 1706830856,
+        "narHash": "sha256-a0NYyp+h9hlb7ddVz4LUn1vT/PLwqfrWYcHMvFB1xYg=",
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "rev": "b253292d9c0a5ead9bc98c4e9a26c6312e27d69f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1685518550,
+        "narHash": "sha256-o2d0KcvaXzTrPRIo0kOLV0/QXHhDQ5DTi+OxcjO8xqY=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "a1720a10a6cfe8234c0e93907ffe81be440f4cef",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "devenv",
+          "pre-commit-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1660459072,
+        "narHash": "sha256-8DFJjXG8zqoONA1vXtgeKXy68KdJL5UaXR8NtVMUbx8=",
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "a20de23b925fd8264fd7fad6454652e142fd7f73",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
+    "lowdown-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1633514407,
+        "narHash": "sha256-Dw32tiMjdK9t3ETl5fzGrutQTzh2rufgZV4A/BbxuD4=",
+        "owner": "kristapsdz",
+        "repo": "lowdown",
+        "rev": "d2c2b44ff6c27b936ec27358a2653caaef8f73b8",
+        "type": "github"
+      },
+      "original": {
+        "owner": "kristapsdz",
+        "repo": "lowdown",
+        "type": "github"
+      }
+    },
+    "nix": {
+      "inputs": {
+        "lowdown-src": "lowdown-src",
+        "nixpkgs": [
+          "devenv",
+          "nixpkgs"
+        ],
+        "nixpkgs-regression": "nixpkgs-regression"
+      },
+      "locked": {
+        "lastModified": 1676545802,
+        "narHash": "sha256-EK4rZ+Hd5hsvXnzSzk2ikhStJnD63odF7SzsQ8CuSPU=",
+        "owner": "domenkozar",
+        "repo": "nix",
+        "rev": "7c91803598ffbcfe4a55c44ac6d49b2cf07a527f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "domenkozar",
+        "ref": "relaxed-flakes",
+        "repo": "nix",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1678875422,
+        "narHash": "sha256-T3o6NcQPwXjxJMn2shz86Chch4ljXgZn746c2caGxd8=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "126f49a01de5b7e35a43fd43f891ecf6d3a51459",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-lib": {
+      "locked": {
+        "dir": "lib",
+        "lastModified": 1706550542,
+        "narHash": "sha256-UcsnCG6wx++23yeER4Hg18CXWbgNpqNXcHIo5/1Y+hc=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "97b17f32362e475016f942bbdfda4a4a72a8a652",
+        "type": "github"
+      },
+      "original": {
+        "dir": "lib",
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-regression": {
+      "locked": {
+        "lastModified": 1643052045,
+        "narHash": "sha256-uGJ0VXIhWKGXxkeNnq4TvV3CIOkUJ3PAoLZ3HMzNVMw=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "215d4d0fd80ca5163643b03a33fde804a29cc1e2",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "215d4d0fd80ca5163643b03a33fde804a29cc1e2",
+        "type": "github"
+      }
+    },
+    "nixpkgs-stable": {
+      "locked": {
+        "lastModified": 1685801374,
+        "narHash": "sha256-otaSUoFEMM+LjBI1XL/xGB5ao6IwnZOXc47qhIgJe8U=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "c37ca420157f4abc31e26f436c1145f8951ff373",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-23.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1707939175,
+        "narHash": "sha256-D1xan0lgxbmXDyzVqXTiSYHLmAMrMRdD+alKzEO/p3w=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "f7e8132daca31b1e3859ac0fb49741754375ac3d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "pre-commit-hooks": {
+      "inputs": {
+        "flake-compat": [
+          "devenv",
+          "flake-compat"
+        ],
+        "flake-utils": "flake-utils",
+        "gitignore": "gitignore",
+        "nixpkgs": [
+          "devenv",
+          "nixpkgs"
+        ],
+        "nixpkgs-stable": "nixpkgs-stable"
+      },
+      "locked": {
+        "lastModified": 1704725188,
+        "narHash": "sha256-qq8NbkhRZF1vVYQFt1s8Mbgo8knj+83+QlL5LBnYGpI=",
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "rev": "ea96f0c05924341c551a797aaba8126334c505d2",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "devenv": "devenv",
+        "flake-parts": "flake-parts",
+        "nixpkgs": "nixpkgs_2"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,57 @@
+{
+  description = "Viper";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    devenv.url = "github:cachix/devenv";
+  };
+
+  outputs = inputs@{ flake-parts, ... }:
+    flake-parts.lib.mkFlake { inherit inputs; } {
+      imports = [
+        inputs.devenv.flakeModule
+      ];
+
+      systems = [ "x86_64-linux" "x86_64-darwin" "aarch64-darwin" ];
+
+      perSystem = { config, self', inputs', pkgs, system, ... }: rec {
+        devenv.shells = {
+          default = {
+            languages = {
+              go.enable = true;
+              go.package = pkgs.go_1_22;
+            };
+
+            pre-commit.hooks = {
+              nixpkgs-fmt.enable = true;
+              yamllint.enable = true;
+            };
+
+            packages = with pkgs; [
+              gnumake
+
+              golangci-lint
+              yamllint
+            ];
+
+            scripts = {
+              versions.exec = ''
+                go version
+                golangci-lint version
+              '';
+            };
+
+            enterShell = ''
+              versions
+            '';
+
+            # https://github.com/cachix/devenv/issues/528#issuecomment-1556108767
+            containers = pkgs.lib.mkForce { };
+          };
+
+          ci = devenv.shells.default;
+        };
+      };
+    };
+}

fs.go

@@ -1,65 +0,0 @@
-//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

@@ -1,100 +0,0 @@
-//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

@@ -1,69 +1,93 @@
 module github.com/spf13/viper
 
-go 1.17
+go 1.20
 
 require (
-	github.com/fsnotify/fsnotify v1.5.1
+	github.com/fsnotify/fsnotify v1.7.0
 	github.com/hashicorp/hcl v1.0.0
-	github.com/magiconair/properties v1.8.5
-	github.com/mitchellh/mapstructure v1.4.3
-	github.com/pelletier/go-toml v1.9.4
-	github.com/sagikazarmark/crypt v0.3.0
-	github.com/spf13/afero v1.6.0
-	github.com/spf13/cast v1.4.1
-	github.com/spf13/jwalterweatherman v1.1.0
+	github.com/magiconair/properties v1.8.7
+	github.com/mitchellh/mapstructure v1.5.0
+	github.com/pelletier/go-toml/v2 v2.2.1
+	github.com/sagikazarmark/crypt v0.19.0
+	github.com/sagikazarmark/locafero v0.4.0
+	github.com/sagikazarmark/slog-shim v0.1.0
+	github.com/spf13/afero v1.11.0
+	github.com/spf13/cast v1.6.0
 	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 v1.66.2
-	gopkg.in/yaml.v2 v2.4.0
+	github.com/stretchr/testify v1.9.0
+	github.com/subosito/gotenv v1.6.0
+	gopkg.in/ini.v1 v1.67.0
+	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
-	cloud.google.com/go v0.99.0 // indirect
-	cloud.google.com/go/firestore v1.6.1 // indirect
-	github.com/armon/go-metrics v0.3.10 // indirect
-	github.com/census-instrumentation/opencensus-proto v0.3.0 // indirect
-	github.com/cespare/xxhash/v2 v2.1.2 // indirect
-	github.com/cncf/udpa/go v0.0.0-20210930031921-04548b0d99d4 // indirect
-	github.com/cncf/xds/go v0.0.0-20211130200136-a8f946100490 // indirect
+	cloud.google.com/go v0.112.1 // indirect
+	cloud.google.com/go/compute v1.24.0 // indirect
+	cloud.google.com/go/compute/metadata v0.2.3 // indirect
+	cloud.google.com/go/firestore v1.15.0 // indirect
+	cloud.google.com/go/longrunning v0.5.5 // indirect
+	github.com/armon/go-metrics v0.4.1 // indirect
 	github.com/coreos/go-semver v0.3.0 // indirect
-	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/envoyproxy/go-control-plane v0.10.1 // indirect
-	github.com/envoyproxy/protoc-gen-validate v0.6.2 // indirect
-	github.com/fatih/color v1.13.0 // indirect
+	github.com/coreos/go-systemd/v22 v22.3.2 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/fatih/color v1.14.1 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // 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 v0.5.6 // indirect
-	github.com/googleapis/gax-go/v2 v2.1.1 // indirect
-	github.com/hashicorp/consul/api v1.11.0 // indirect
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/google/s2a-go v0.1.7 // indirect
+	github.com/googleapis/enterprise-certificate-proxy v0.3.2 // indirect
+	github.com/googleapis/gax-go/v2 v2.12.3 // indirect
+	github.com/hashicorp/consul/api v1.28.2 // indirect
+	github.com/hashicorp/errwrap v1.1.0 // indirect
 	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect
-	github.com/hashicorp/go-hclog v1.0.0 // indirect
+	github.com/hashicorp/go-hclog v1.5.0 // indirect
 	github.com/hashicorp/go-immutable-radix v1.3.1 // indirect
+	github.com/hashicorp/go-multierror v1.1.1 // indirect
 	github.com/hashicorp/go-rootcerts v1.0.2 // indirect
 	github.com/hashicorp/golang-lru v0.5.4 // indirect
-	github.com/hashicorp/serf v0.9.6 // 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/klauspost/compress v1.17.2 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.17 // 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/pmezard/go-difflib v1.0.0 // indirect
-	go.etcd.io/etcd/api/v3 v3.5.1 // indirect
-	go.etcd.io/etcd/client/pkg/v3 v3.5.1 // indirect
-	go.etcd.io/etcd/client/v2 v2.305.1 // indirect
-	go.opencensus.io v0.23.0 // indirect
-	golang.org/x/crypto v0.0.0-20210817164053-32db794688a5 // indirect
-	golang.org/x/net v0.0.0-20210813160813-60bc85c4be6d // indirect
-	golang.org/x/oauth2 v0.0.0-20211104180415-d3ed0bb246c8 // indirect
-	golang.org/x/sys v0.0.0-20211205182925-97ca703d548d // indirect
-	golang.org/x/text v0.3.7 // indirect
-	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
-	google.golang.org/api v0.62.0 // indirect
-	google.golang.org/appengine v1.6.7 // indirect
-	google.golang.org/genproto v0.0.0-20211208223120-3a66f561d7aa // indirect
-	google.golang.org/grpc v1.42.0 // indirect
-	google.golang.org/protobuf v1.27.1 // indirect
-	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
+	github.com/nats-io/nats.go v1.34.0 // indirect
+	github.com/nats-io/nkeys v0.4.7 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
+	github.com/sourcegraph/conc v0.3.0 // indirect
+	go.etcd.io/etcd/api/v3 v3.5.12 // indirect
+	go.etcd.io/etcd/client/pkg/v3 v3.5.12 // indirect
+	go.etcd.io/etcd/client/v2 v2.305.12 // indirect
+	go.etcd.io/etcd/client/v3 v3.5.12 // indirect
+	go.opencensus.io v0.24.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.49.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.49.0 // indirect
+	go.opentelemetry.io/otel v1.24.0 // indirect
+	go.opentelemetry.io/otel/metric v1.24.0 // indirect
+	go.opentelemetry.io/otel/trace v1.24.0 // indirect
+	go.uber.org/atomic v1.9.0 // indirect
+	go.uber.org/multierr v1.9.0 // indirect
+	go.uber.org/zap v1.21.0 // indirect
+	golang.org/x/crypto v0.21.0 // indirect
+	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
+	golang.org/x/net v0.23.0 // indirect
+	golang.org/x/oauth2 v0.18.0 // indirect
+	golang.org/x/sync v0.6.0 // indirect
+	golang.org/x/sys v0.18.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	golang.org/x/time v0.5.0 // indirect
+	google.golang.org/api v0.171.0 // indirect
+	google.golang.org/appengine v1.6.8 // indirect
+	google.golang.org/genproto v0.0.0-20240213162025-012b6fc9bca9 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20240311132316-a219d84964c2 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20240314234333-6e1732d8331c // indirect
+	google.golang.org/grpc v1.62.1 // indirect
+	google.golang.org/protobuf v1.33.0 // indirect
 )

internal/encoding/decoder.go

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

internal/encoding/decoder_test.go

@@ -2,15 +2,19 @@ package encoding
 
 import (
 	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 type decoder struct {
-	v interface{}
+	v map[string]any
 }
 
-func (d decoder) Decode(_ []byte, v interface{}) error {
-	rv := v.(*string)
-	*rv = d.v.(string)
+func (d decoder) Decode(_ []byte, v map[string]any) error {
+	for key, value := range d.v {
+		v[key] = value
+	}
 
 	return nil
 }
@@ -20,23 +24,17 @@ func TestDecoderRegistry_RegisterDecoder(t *testing.T) {
 		registry := NewDecoderRegistry()
 
 		err := registry.RegisterDecoder("myformat", decoder{})
-		if err != nil {
-			t.Fatal(err)
-		}
+		require.NoError(t, err)
 	})
 
 	t.Run("AlreadyRegistered", func(t *testing.T) {
 		registry := NewDecoderRegistry()
 
 		err := registry.RegisterDecoder("myformat", decoder{})
-		if err != nil {
-			t.Fatal(err)
-		}
+		require.NoError(t, err)
 
 		err = registry.RegisterDecoder("myformat", decoder{})
-		if err != ErrDecoderFormatAlreadyRegistered {
-			t.Fatalf("expected ErrDecoderFormatAlreadyRegistered, got: %v", err)
-		}
+		assert.ErrorIs(t, err, ErrDecoderFormatAlreadyRegistered)
 	})
 }
 
@@ -44,34 +42,28 @@ func TestDecoderRegistry_Decode(t *testing.T) {
 	t.Run("OK", func(t *testing.T) {
 		registry := NewDecoderRegistry()
 		decoder := decoder{
-			v: "decoded value",
+			v: map[string]any{
+				"key": "value",
+			},
 		}
 
 		err := registry.RegisterDecoder("myformat", decoder)
-		if err != nil {
-			t.Fatal(err)
-		}
+		require.NoError(t, err)
 
-		var v string
+		v := map[string]any{}
 
-		err = registry.Decode("myformat", []byte("some value"), &v)
-		if err != nil {
-			t.Fatal(err)
-		}
+		err = registry.Decode("myformat", []byte("key: value"), v)
+		require.NoError(t, err)
 
-		if v != "decoded value" {
-			t.Fatalf("expected 'decoded value', got: %#v", v)
-		}
+		assert.Equal(t, decoder.v, v)
 	})
 
 	t.Run("DecoderNotFound", func(t *testing.T) {
 		registry := NewDecoderRegistry()
 
-		var v string
+		v := map[string]any{}
 
-		err := registry.Decode("myformat", []byte("some value"), &v)
-		if err != ErrDecoderNotFound {
-			t.Fatalf("expected ErrDecoderNotFound, got: %v", err)
-		}
+		err := registry.Decode("myformat", nil, v)
+		assert.ErrorIs(t, err, ErrDecoderNotFound)
 	})
 }

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]any) ([]byte, error) {
+	flattened := map[string]any{}
+
+	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]any) 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 +1,55 @@
+package dotenv
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// original form of the data.
+const original = `# key-value pair
+KEY=value
+`
+
+// encoded form of the data.
+const encoded = `KEY=value
+`
+
+// data is Viper's internal representation.
+var data = map[string]any{
+	"KEY": "value",
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, encoded, string(b))
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(original), v)
+		require.NoError(t, err)
+
+		assert.Equal(t, data, v)
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		require.Error(t, err)
+
+		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 the main package.
+// TODO: move it to a common place.
+func flattenAndMergeMap(shadow, m map[string]any, prefix, delimiter string) map[string]any {
+	if shadow != nil && prefix != "" && shadow[prefix] != nil {
+		// prefix is shadowed => nothing more to flatten
+		return shadow
+	}
+	if shadow == nil {
+		shadow = make(map[string]any)
+	}
+
+	var m2 map[string]any
+	if prefix != "" {
+		prefix += delimiter
+	}
+	for k, val := range m {
+		fullKey := prefix + k
+		switch val := val.(type) {
+		case map[string]any:
+			m2 = val
+		case map[any]any:
+			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

@@ -5,9 +5,9 @@ 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.
+// It's primarily used for encoding a map[string]any into a file format.
 type Encoder interface {
-	Encode(v interface{}) ([]byte, error)
+	Encode(v map[string]any) ([]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]any) ([]byte, error) {
 	e.mu.RLock()
 	encoder, ok := e.encoders[format]
 	e.mu.RUnlock()

internal/encoding/encoder_test.go

@@ -2,13 +2,16 @@ package encoding
 
 import (
 	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 type encoder struct {
 	b []byte
 }
 
-func (e encoder) Encode(_ interface{}) ([]byte, error) {
+func (e encoder) Encode(_ map[string]any) ([]byte, error) {
 	return e.b, nil
 }
 
@@ -17,23 +20,17 @@ func TestEncoderRegistry_RegisterEncoder(t *testing.T) {
 		registry := NewEncoderRegistry()
 
 		err := registry.RegisterEncoder("myformat", encoder{})
-		if err != nil {
-			t.Fatal(err)
-		}
+		require.NoError(t, err)
 	})
 
 	t.Run("AlreadyRegistered", func(t *testing.T) {
 		registry := NewEncoderRegistry()
 
 		err := registry.RegisterEncoder("myformat", encoder{})
-		if err != nil {
-			t.Fatal(err)
-		}
+		require.NoError(t, err)
 
 		err = registry.RegisterEncoder("myformat", encoder{})
-		if err != ErrEncoderFormatAlreadyRegistered {
-			t.Fatalf("expected ErrEncoderFormatAlreadyRegistered, got: %v", err)
-		}
+		assert.ErrorIs(t, err, ErrEncoderFormatAlreadyRegistered)
 	})
 }
 
@@ -41,30 +38,22 @@ 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)
-		if err != nil {
-			t.Fatal(err)
-		}
+		require.NoError(t, err)
 
-		b, err := registry.Encode("myformat", "some value")
-		if err != nil {
-			t.Fatal(err)
-		}
+		b, err := registry.Encode("myformat", map[string]any{"key": "value"})
+		require.NoError(t, err)
 
-		if string(b) != "encoded value" {
-			t.Fatalf("expected 'encoded value', got: %#v", string(b))
-		}
+		assert.Equal(t, "key: value", string(b))
 	})
 
 	t.Run("EncoderNotFound", func(t *testing.T) {
 		registry := NewEncoderRegistry()
 
-		_, err := registry.Encode("myformat", "some value")
-		if err != ErrEncoderNotFound {
-			t.Fatalf("expected ErrEncoderNotFound, got: %v", err)
-		}
+		_, err := registry.Encode("myformat", map[string]any{"key": "value"})
+		assert.ErrorIs(t, err, ErrEncoderNotFound)
 	})
 }

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]any) ([]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]any) error {
+	return hcl.Unmarshal(b, &v)
 }

internal/encoding/hcl/codec_test.go

@@ -0,0 +1,132 @@
+package hcl
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// 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
+// (e.g. map is decoded into a list of maps).
+var decoded = map[string]any{
+	"key": "value",
+	"list": []any{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": []map[string]any{
+		{
+			"key": "value",
+		},
+	},
+	"nested_map": []map[string]any{
+		{
+			"map": []map[string]any{
+				{
+					"key": "value",
+					"list": []any{
+						"item1",
+						"item2",
+						"item3",
+					},
+				},
+			},
+		},
+	},
+}
+
+// data is Viper's internal representation.
+var data = map[string]any{
+	"key": "value",
+	"list": []any{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]any{
+		"key": "value",
+	},
+	"nested_map": map[string]any{
+		"map": map[string]any{
+			"key": "value",
+			"list": []any{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, encoded, string(b))
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(original), v)
+		require.NoError(t, err)
+
+		assert.Equal(t, decoded, v)
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		require.Error(t, err)
+
+		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]any) ([]byte, error) {
+	cfg := ini.Empty()
+	ini.PrettyFormat = false
+
+	flattened := map[string]any{}
+
+	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]any) 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 +1,99 @@
+package ini
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// 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
+// (e.g. top level keys land in a section called default).
+var decoded = map[string]any{
+	"DEFAULT": map[string]any{
+		"key": "value",
+	},
+	"map": map[string]any{
+		"key": "value",
+	},
+}
+
+// data is Viper's internal representation.
+var data = map[string]any{
+	"key": "value",
+	"map": map[string]any{
+		"key": "value",
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		b, err := codec.Encode(data)
+		require.NoError(t, err)
+
+		assert.Equal(t, encoded, string(b))
+	})
+
+	t.Run("Default", func(t *testing.T) {
+		codec := Codec{}
+
+		data := map[string]any{
+			"default": map[string]any{
+				"key": "value",
+			},
+			"map": map[string]any{
+				"key": "value",
+			},
+		}
+
+		b, err := codec.Encode(data)
+		require.NoError(t, err)
+
+		assert.Equal(t, encoded, string(b))
+	})
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(original), v)
+		require.NoError(t, err)
+
+		assert.Equal(t, decoded, v)
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		require.Error(t, err)
+
+		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]any, path []string) map[string]any {
+	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]any)
+			m[k] = m3
+			m = m3
+			continue
+		}
+		m3, ok := m2.(map[string]any)
+		if !ok {
+			// intermediate key is a value
+			// => replace with a new map
+			m3 = make(map[string]any)
+			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 the main package.
+// TODO: move it to a common place.
+func flattenAndMergeMap(shadow, m map[string]any, prefix, delimiter string) map[string]any {
+	if shadow != nil && prefix != "" && shadow[prefix] != nil {
+		// prefix is shadowed => nothing more to flatten
+		return shadow
+	}
+	if shadow == nil {
+		shadow = make(map[string]any)
+	}
+
+	var m2 map[string]any
+	if prefix != "" {
+		prefix += delimiter
+	}
+	for k, val := range m {
+		fullKey := prefix + k
+		switch val := val.(type) {
+		case map[string]any:
+			m2 = val
+		case map[any]any:
+			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]any) ([]byte, error) {
+	if c.Properties == nil {
+		c.Properties = properties.NewProperties()
+	}
+
+	flattened := map[string]any{}
+
+	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]any) 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 +1,75 @@
+package javaproperties
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// 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
+`
+
+// data is Viper's internal representation.
+var data = map[string]any{
+	"key": "value",
+	"map": map[string]any{
+		"key": "value",
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, encoded, string(b))
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(original), v)
+		require.NoError(t, err)
+
+		assert.Equal(t, data, v)
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		t.Skip("TODO: needs invalid data example")
+
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		codec.Decode([]byte(``), v)
+
+		assert.Empty(t, v)
+	})
+}
+
+func TestCodec_DecodeEncode(t *testing.T) {
+	codec := Codec{}
+
+	v := map[string]any{}
+
+	err := codec.Decode([]byte(original), v)
+	require.NoError(t, err)
+
+	b, err := codec.Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, original, string(b))
+}

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]any, path []string) map[string]any {
+	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]any)
+			m[k] = m3
+			m = m3
+			continue
+		}
+		m3, ok := m2.(map[string]any)
+		if !ok {
+			// intermediate key is a value
+			// => replace with a new map
+			m3 = make(map[string]any)
+			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 the main package.
+// TODO: move it to a common place.
+func flattenAndMergeMap(shadow, m map[string]any, prefix, delimiter string) map[string]any {
+	if shadow != nil && prefix != "" && shadow[prefix] != nil {
+		// prefix is shadowed => nothing more to flatten
+		return shadow
+	}
+	if shadow == nil {
+		shadow = make(map[string]any)
+	}
+
+	var m2 map[string]any
+	if prefix != "" {
+		prefix += delimiter
+	}
+	for k, val := range m {
+		fullKey := prefix + k
+		switch val := val.(type) {
+		case map[string]any:
+			m2 = val
+		case map[any]any:
+			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]any) ([]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]any) error {
+	return json.Unmarshal(b, &v)
 }

internal/encoding/json/codec_test.go

@@ -0,0 +1,87 @@
+package json
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// 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"
+      ]
+    }
+  }
+}`
+
+// data is Viper's internal representation.
+var data = map[string]any{
+	"key": "value",
+	"list": []any{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]any{
+		"key": "value",
+	},
+	"nested_map": map[string]any{
+		"map": map[string]any{
+			"key": "value",
+			"list": []any{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, encoded, string(b))
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(encoded), v)
+		require.NoError(t, err)
+
+		assert.Equal(t, data, v)
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		require.Error(t, err)
+
+		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]any) ([]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]any) error {
+	return toml.Unmarshal(b, &v)
 }

internal/encoding/toml/codec_test.go

@@ -0,0 +1,97 @@
+package toml
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// 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']
+`
+
+// data is Viper's internal representation.
+var data = map[string]any{
+	"key": "value",
+	"list": []any{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]any{
+		"key": "value",
+	},
+	"nested_map": map[string]any{
+		"map": map[string]any{
+			"key": "value",
+			"list": []any{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, encoded, string(b))
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(original), v)
+		require.NoError(t, err)
+
+		assert.Equal(t, data, v)
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		require.Error(t, err)
+
+		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]any) ([]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]any) error {
+	return yaml.Unmarshal(b, &v)
 }

internal/encoding/yaml/codec_test.go

@@ -0,0 +1,128 @@
+package yaml
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// 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
+// (e.g. map is decoded into a map with interface key).
+var decoded = map[string]any{
+	"key": "value",
+	"list": []any{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]any{
+		"key": "value",
+	},
+	"nested_map": map[string]any{
+		"map": map[string]any{
+			"key": "value",
+			"list": []any{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+// data is Viper's internal representation.
+var data = map[string]any{
+	"key": "value",
+	"list": []any{
+		"item1",
+		"item2",
+		"item3",
+	},
+	"map": map[string]any{
+		"key": "value",
+	},
+	"nested_map": map[string]any{
+		"map": map[string]any{
+			"key": "value",
+			"list": []any{
+				"item1",
+				"item2",
+				"item3",
+			},
+		},
+	},
+}
+
+func TestCodec_Encode(t *testing.T) {
+	codec := Codec{}
+
+	b, err := codec.Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, encoded, string(b))
+}
+
+func TestCodec_Decode(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(original), v)
+		require.NoError(t, err)
+
+		assert.Equal(t, decoded, v)
+	})
+
+	t.Run("InvalidData", func(t *testing.T) {
+		codec := Codec{}
+
+		v := map[string]any{}
+
+		err := codec.Decode([]byte(`invalid data`), v)
+		require.Error(t, err)
+
+		t.Logf("decoding failed as expected: %s", err)
+	})
+}

internal/features/bind_struct.go

@@ -0,0 +1,5 @@
+//go:build viper_bind_struct
+
+package features
+
+const BindStruct = true

internal/features/bind_struct_default.go

@@ -0,0 +1,5 @@
+//go:build !viper_bind_struct
+
+package features
+
+const BindStruct = false

internal/testutil/env_go1_16.go

@@ -1,40 +0,0 @@
-//go:build !go1.17
-// +build !go1.17
-
-package testutil
-
-import (
-	"os"
-	"testing"
-)
-
-// Based on https://github.com/frankban/quicktest/blob/577841610793d24f99e31cc2c0ef3a541fefd7c7/patch.go#L34-L64
-// Licensed under the MIT license
-// Copyright (c) 2017 Canonical Ltd.
-
-// Setenv sets an environment variable to a temporary value for the
-// duration of the test.
-//
-// At the end of the test (see "Deferred execution" in the package docs), the
-// environment variable is returned to its original value.
-func Setenv(t *testing.T, name, val string) {
-	setenv(t, name, val, true)
-}
-
-// 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) {
-	oldVal, oldOK := os.LookupEnv(name)
-	if valOK {
-		os.Setenv(name, val)
-	} else {
-		os.Unsetenv(name)
-	}
-	t.Cleanup(func() {
-		if oldOK {
-			os.Setenv(name, oldVal)
-		} else {
-			os.Unsetenv(name)
-		}
-	})
-}

internal/testutil/env_go1_17.go

@@ -1,18 +0,0 @@
-//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)
-}

logger.go

@@ -1,77 +1,68 @@
 package viper
 
 import (
-	"fmt"
+	"context"
 
-	jww "github.com/spf13/jwalterweatherman"
+	slog "github.com/sagikazarmark/slog-shim"
 )
 
 // Logger is a unified interface for various logging use cases and practices, including:
-// 		- leveled logging
-// 		- structured logging
+//   - leveled logging
+//   - structured logging
+//
+// Deprecated: use `log/slog` instead.
 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{})
+	Trace(msg string, keyvals ...any)
 
 	// Debug logs a Debug event.
 	//
 	// A verbose series of information events.
 	// They are useful when debugging the system.
-	Debug(msg string, keyvals ...interface{})
+	Debug(msg string, keyvals ...any)
 
 	// Info logs an Info event.
 	//
 	// General information about what's happening inside the system.
-	Info(msg string, keyvals ...interface{})
+	Info(msg string, keyvals ...any)
 
 	// Warn logs a Warn(ing) event.
 	//
 	// Non-critical events that should be looked at.
-	Warn(msg string, keyvals ...interface{})
+	Warn(msg string, keyvals ...any)
 
 	// 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{})
+	// but exiting and panicking is out of scope for a logging library.
+	Error(msg string, keyvals ...any)
 }
 
-type jwwLogger struct{}
-
-func (jwwLogger) Trace(msg string, keyvals ...interface{}) {
-	jww.TRACE.Printf(jwwLogMessage(msg, keyvals...))
+// WithLogger sets a custom logger.
+func WithLogger(l *slog.Logger) Option {
+	return optionFunc(func(v *Viper) {
+		v.logger = l
+	})
 }
 
-func (jwwLogger) Debug(msg string, keyvals ...interface{}) {
-	jww.DEBUG.Printf(jwwLogMessage(msg, keyvals...))
+type discardHandler struct{}
+
+func (n *discardHandler) Enabled(_ context.Context, _ slog.Level) bool {
+	return false
 }
 
-func (jwwLogger) Info(msg string, keyvals ...interface{}) {
-	jww.INFO.Printf(jwwLogMessage(msg, keyvals...))
+func (n *discardHandler) Handle(_ context.Context, _ slog.Record) error {
+	return nil
 }
 
-func (jwwLogger) Warn(msg string, keyvals ...interface{}) {
-	jww.WARN.Printf(jwwLogMessage(msg, keyvals...))
+func (n *discardHandler) WithAttrs(_ []slog.Attr) slog.Handler {
+	return n
 }
 
-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
+func (n *discardHandler) WithGroup(_ string) slog.Handler {
+	return n
 }

overrides_test.go

@@ -1,7 +1,6 @@
 package viper
 
 import (
-	"fmt"
 	"strings"
 	"testing"
 
@@ -46,11 +45,11 @@ func TestNestedOverrides(t *testing.T) {
 	deepCheckValue(assert, v, overrideLayer, []string{"tom", "size"}, 4)
 
 	// Case 4: key:value overridden by a map
-	v = overrideDefault(assert, "tom.size", 4, "tom", map[string]interface{}{"age": 10}) // "tom.size" is first given "4" as default value, then "tom" is overridden by map{"age":10}
-	assert.Equal(4, v.Get("tom.size"))                                                   // "tom.size" should still be reachable
-	assert.Equal(10, v.Get("tom.age"))                                                   // new value should be there
-	deepCheckValue(assert, v, overrideLayer, []string{"tom", "age"}, 10)                 // new value should be there
-	v = override(assert, "tom.size", 4, "tom", map[string]interface{}{"age": 10})
+	v = overrideDefault(assert, "tom.size", 4, "tom", map[string]any{"age": 10}) // "tom.size" is first given "4" as default value, then "tom" is overridden by map{"age":10}
+	assert.Equal(4, v.Get("tom.size"))                                           // "tom.size" should still be reachable
+	assert.Equal(10, v.Get("tom.age"))                                           // new value should be there
+	deepCheckValue(assert, v, overrideLayer, []string{"tom", "age"}, 10)         // new value should be there
+	v = override(assert, "tom.size", 4, "tom", map[string]any{"age": 10})
 	assert.Nil(v.Get("tom.size"))
 	assert.Equal(10, v.Get("tom.age"))
 	deepCheckValue(assert, v, overrideLayer, []string{"tom", "age"}, 10)
@@ -75,11 +74,11 @@ func TestNestedOverrides(t *testing.T) {
 	}
 }
 
-func overrideDefault(assert *assert.Assertions, firstPath string, firstValue interface{}, secondPath string, secondValue interface{}) *Viper {
+func overrideDefault(assert *assert.Assertions, firstPath string, firstValue any, secondPath string, secondValue any) *Viper {
 	return overrideFromLayer(defaultLayer, assert, firstPath, firstValue, secondPath, secondValue)
 }
 
-func override(assert *assert.Assertions, firstPath string, firstValue interface{}, secondPath string, secondValue interface{}) *Viper {
+func override(assert *assert.Assertions, firstPath string, firstValue any, secondPath string, secondValue any) *Viper {
 	return overrideFromLayer(overrideLayer, assert, firstPath, firstValue, secondPath, secondValue)
 }
 
@@ -94,11 +93,11 @@ func override(assert *assert.Assertions, firstPath string, firstValue interface{
 //
 // After each assignment, the value is checked, retrieved both by its full path
 // and by its key sequence (successive maps).
-func overrideFromLayer(l layer, assert *assert.Assertions, firstPath string, firstValue interface{}, secondPath string, secondValue interface{}) *Viper {
+func overrideFromLayer(l layer, assert *assert.Assertions, firstPath string, firstValue any, secondPath string, secondValue any) *Viper {
 	v := New()
 	firstKeys := strings.Split(firstPath, v.keyDelim)
 	if assert == nil ||
-		len(firstKeys) == 0 || len(firstKeys[0]) == 0 {
+		len(firstKeys) == 0 || firstKeys[0] == "" {
 		return v
 	}
 
@@ -116,7 +115,7 @@ func overrideFromLayer(l layer, assert *assert.Assertions, firstPath string, fir
 
 	// Override and check new value
 	secondKeys := strings.Split(secondPath, v.keyDelim)
-	if len(secondKeys) == 0 || len(secondKeys[0]) == 0 {
+	if len(secondKeys) == 0 || secondKeys[0] == "" {
 		return v
 	}
 	v.Set(secondPath, secondValue)
@@ -127,15 +126,15 @@ func overrideFromLayer(l layer, assert *assert.Assertions, firstPath string, fir
 }
 
 // deepCheckValue checks that all given keys correspond to a valid path in the
-// configuration map of the given layer, and that the final value equals the one given
-func deepCheckValue(assert *assert.Assertions, v *Viper, l layer, keys []string, value interface{}) {
+// configuration map of the given layer, and that the final value equals the one given.
+func deepCheckValue(assert *assert.Assertions, v *Viper, l layer, keys []string, value any) {
 	if assert == nil || v == nil ||
-		len(keys) == 0 || len(keys[0]) == 0 {
+		len(keys) == 0 || keys[0] == "" {
 		return
 	}
 
 	// init
-	var val interface{}
+	var val any
 	var ms string
 	switch l {
 	case defaultLayer:
@@ -147,28 +146,25 @@ func deepCheckValue(assert *assert.Assertions, v *Viper, l layer, keys []string,
 	}
 
 	// loop through map
-	var m map[string]interface{}
-	err := false
+	var m map[string]any
 	for _, k := range keys {
 		if val == nil {
-			assert.Fail(fmt.Sprintf("%s is not a map[string]interface{}", ms))
+			assert.Failf("%s is not a map[string]any", ms)
 			return
 		}
 
 		// deep scan of the map to get the final value
-		switch val.(type) {
-		case map[interface{}]interface{}:
+		switch val := val.(type) {
+		case map[any]any:
 			m = cast.ToStringMap(val)
-		case map[string]interface{}:
-			m = val.(map[string]interface{})
+		case map[string]any:
+			m = val
 		default:
-			assert.Fail(fmt.Sprintf("%s is not a map[string]interface{}", ms))
+			assert.Failf("%s is not a map[string]any", ms)
 			return
 		}
 		ms = ms + "[\"" + k + "\"]"
 		val = m[k]
 	}
-	if !err {
-		assert.Equal(value, val)
-	}
+	assert.Equal(value, val)
 }

remote/remote.go

@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"io"
 	"os"
+	"strings"
 
 	crypt "github.com/sagikazarmark/crypt/config"
 
@@ -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 +86,28 @@ 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)
+		case "nats":
+			cm, err = crypt.NewNatsConfigManager(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)
+		case "nats":
+			cm, err = crypt.NewStandardNatsConfigManager(endpoints)
 		default:
-			cm, err = crypt.NewStandardConsulConfigManager([]string{rp.Endpoint()})
+			cm, err = crypt.NewStandardConsulConfigManager(endpoints)
 		}
 	}
 	if err != nil {

util.go

@@ -18,6 +18,7 @@ import (
 	"strings"
 	"unicode"
 
+	slog "github.com/sagikazarmark/slog-shim"
 	"github.com/spf13/cast"
 )
 
@@ -31,13 +32,18 @@ func (pe ConfigParseError) Error() string {
 	return fmt.Sprintf("While parsing config: %s", pe.err.Error())
 }
 
+// Unwrap returns the wrapped error.
+func (pe ConfigParseError) Unwrap() error {
+	return pe.err
+}
+
 // toCaseInsensitiveValue checks if the value is a  map;
 // if so, create a copy and lower-case the keys recursively.
-func toCaseInsensitiveValue(value interface{}) interface{} {
+func toCaseInsensitiveValue(value any) any {
 	switch v := value.(type) {
-	case map[interface{}]interface{}:
+	case map[any]any:
 		value = copyAndInsensitiviseMap(cast.ToStringMap(v))
-	case map[string]interface{}:
+	case map[string]any:
 		value = copyAndInsensitiviseMap(v)
 	}
 
@@ -46,15 +52,15 @@ func toCaseInsensitiveValue(value interface{}) interface{} {
 
 // copyAndInsensitiviseMap behaves like insensitiviseMap, but creates a copy of
 // any map it makes case insensitive.
-func copyAndInsensitiviseMap(m map[string]interface{}) map[string]interface{} {
-	nm := make(map[string]interface{})
+func copyAndInsensitiviseMap(m map[string]any) map[string]any {
+	nm := make(map[string]any)
 
 	for key, val := range m {
 		lkey := strings.ToLower(key)
 		switch v := val.(type) {
-		case map[interface{}]interface{}:
+		case map[any]any:
 			nm[lkey] = copyAndInsensitiviseMap(cast.ToStringMap(v))
-		case map[string]interface{}:
+		case map[string]any:
 			nm[lkey] = copyAndInsensitiviseMap(v)
 		default:
 			nm[lkey] = v
@@ -64,18 +70,25 @@ func copyAndInsensitiviseMap(m map[string]interface{}) map[string]interface{} {
 	return nm
 }
 
-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{}))
-		}
+func insensitiviseVal(val any) any {
+	switch v := val.(type) {
+	case map[any]any:
+		// nested map: cast and recursively insensitivise
+		val = cast.ToStringMap(val)
+		insensitiviseMap(val.(map[string]any))
+	case map[string]any:
+		// nested map: recursively insensitivise
+		insensitiviseMap(v)
+	case []any:
+		// nested array: recursively insensitivise
+		insensitiveArray(v)
+	}
+	return val
+}
 
+func insensitiviseMap(m map[string]any) {
+	for key, val := range m {
+		val = insensitiviseVal(val)
 		lower := strings.ToLower(key)
 		if key != lower {
 			// remove old key (not lower-cased)
@@ -86,7 +99,13 @@ func insensitiviseMap(m map[string]interface{}) {
 	}
 }
 
-func absPathify(logger Logger, inPath string) string {
+func insensitiveArray(a []any) {
+	for i, val := range a {
+		a[i] = insensitiviseVal(val)
+	}
+}
+
+func absPathify(logger *slog.Logger, inPath string) string {
 	logger.Info("trying to resolve absolute path", "path", inPath)
 
 	if inPath == "$HOME" || strings.HasPrefix(inPath, "$HOME"+string(os.PathSeparator)) {
@@ -137,7 +156,7 @@ func safeMul(a, b uint) uint {
 	return c
 }
 
-// parseSizeInBytes converts strings like 1GB or 12 mb into an unsigned integer number of bytes
+// parseSizeInBytes converts strings like 1GB or 12 mb into an unsigned integer number of bytes.
 func parseSizeInBytes(sizeStr string) uint {
 	sizeStr = strings.TrimSpace(sizeStr)
 	lastChar := len(sizeStr) - 1
@@ -179,22 +198,22 @@ func parseSizeInBytes(sizeStr string) uint {
 // 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{} {
+func deepSearch(m map[string]any, path []string) map[string]any {
 	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{})
+			m3 := make(map[string]any)
 			m[k] = m3
 			m = m3
 			continue
 		}
-		m3, ok := m2.(map[string]interface{})
+		m3, ok := m2.(map[string]any)
 		if !ok {
 			// intermediate key is a value
 			// => replace with a new map
-			m3 = make(map[string]interface{})
+			m3 = make(map[string]any)
 			m[k] = m3
 		}
 		// continue search from here

util_test.go

@@ -13,24 +13,24 @@ package viper
 import (
 	"os"
 	"path/filepath"
-	"reflect"
 	"testing"
 
-	"github.com/spf13/viper/internal/testutil"
+	slog "github.com/sagikazarmark/slog-shim"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestCopyAndInsensitiviseMap(t *testing.T) {
 	var (
-		given = map[string]interface{}{
+		given = map[string]any{
 			"Foo": 32,
-			"Bar": map[interface{}]interface{}{
+			"Bar": map[any]any{
 				"ABc": "A",
 				"cDE": "B",
 			},
 		}
-		expected = map[string]interface{}{
+		expected = map[string]any{
 			"foo": 32,
-			"bar": map[string]interface{}{
+			"bar": map[string]any{
 				"abc": "A",
 				"cde": "B",
 			},
@@ -39,22 +39,15 @@ func TestCopyAndInsensitiviseMap(t *testing.T) {
 
 	got := copyAndInsensitiviseMap(given)
 
-	if !reflect.DeepEqual(got, expected) {
-		t.Fatalf("Got %q\nexpected\n%q", got, expected)
-	}
+	assert.Equal(t, expected, got)
+	_, ok := given["foo"]
+	assert.False(t, ok)
+	_, ok = given["bar"]
+	assert.False(t, ok)
 
-	if _, ok := given["foo"]; ok {
-		t.Fatal("Input map changed")
-	}
-
-	if _, ok := given["bar"]; ok {
-		t.Fatal("Input map changed")
-	}
-
-	m := given["Bar"].(map[interface{}]interface{})
-	if _, ok := m["ABc"]; !ok {
-		t.Fatal("Input map changed")
-	}
+	m := given["Bar"].(map[any]any)
+	_, ok = m["ABc"]
+	assert.True(t, ok)
 }
 
 func TestAbsPathify(t *testing.T) {
@@ -64,8 +57,8 @@ func TestAbsPathify(t *testing.T) {
 	homer := filepath.Join(home, "homer")
 	wd, _ := os.Getwd()
 
-	testutil.Setenv(t, "HOMER_ABSOLUTE_PATH", homer)
-	testutil.Setenv(t, "VAR_WITH_RELATIVE_PATH", "relative")
+	t.Setenv("HOMER_ABSOLUTE_PATH", homer)
+	t.Setenv("VAR_WITH_RELATIVE_PATH", "relative")
 
 	tests := []struct {
 		input  string
@@ -87,9 +80,7 @@ func TestAbsPathify(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		got := absPathify(jwwLogger{}, test.input)
-		if got != test.output {
-			t.Errorf("Got %v\nexpected\n%q", got, test.output)
-		}
+		got := absPathify(slog.Default(), test.input)
+		assert.Equal(t, test.output, got)
 	}
 }

viper_go1_16.go

@@ -1,32 +0,0 @@
-//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_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

@@ -1,12 +0,0 @@
-//go:build !js
-// +build !js
-
-package viper
-
-import "github.com/fsnotify/fsnotify"
-
-type watcher = fsnotify.Watcher
-
-func newWatcher() (*watcher, error) {
-	return fsnotify.NewWatcher()
-}

watch_wasm.go

@@ -1,30 +0,0 @@
-// +build js,wasm
-
-package viper
-
-import (
-	"errors"
-
-	"github.com/fsnotify/fsnotify"
-)
-
-type watcher struct {
-	Events chan fsnotify.Event
-	Errors chan error
-}
-
-func (*watcher) Close() error {
-	return nil
-}
-
-func (*watcher) Add(name string) error {
-	return nil
-}
-
-func (*watcher) Remove(name string) error {
-	return nil
-}
-
-func newWatcher() (*watcher, error) {
-	return &watcher{}, errors.New("fsnotify is not supported on WASM")
-}