fix: config type check when loading any config

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

.github/workflows/ci.yaml

@@ -26,7 +26,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@3041bf56c941b39c61721a86cd11f3bb1338122a # v5.2.0
         with:
-          go-version: "1.23"
+          go-version: "1.24"
 
       - name: Build
         run: go build .
@@ -44,7 +44,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        go: ["1.21", "1.22", "1.23"]
+        go: ["1.21", "1.22", "1.23", "1.24"]
         tags: ["", "viper_finder", "viper_bind_struct"]
 
     steps:
@@ -75,12 +75,12 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@3041bf56c941b39c61721a86cd11f3bb1338122a # v5.2.0
         with:
-          go-version: "1.23"
+          go-version: "1.24"
 
       - name: Lint
         uses: golangci/golangci-lint-action@971e284b6050e8a5849b72094c50ab08da042db8 # v6.1.1
         with:
-          version: v1.60.3
+          version: v1.64.5
 
   dev:
     name: Developer environment

.golangci.yaml

@@ -17,8 +17,6 @@ linters-settings:
         disabled-checks:
             - importShadow
             - unnamedResult
-    golint:
-        min-confidence: 0
     goimports:
         local-prefixes: github.com/spf13/viper
 
@@ -30,7 +28,6 @@ linters:
         - dupl
         - durationcheck
         - exhaustive
-        - exportloopref
         - gci
         - gocritic
         - godot

UPDATES.md

@@ -0,0 +1,126 @@
+# Update Log
+
+**This document details any major updates required to use new features or improvements in Viper.**
+
+## v1.20.x
+
+### New file searching API
+
+Viper now includes a new file searching API that allows users to customize how Viper looks for config files.
+
+Viper accepts a custom [`Finder`](https://pkg.go.dev/github.com/spf13/viper#Finder) interface implementation:
+
+```go
+// Finder looks for files and directories in an [afero.Fs] filesystem.
+type Finder interface {
+	Find(fsys afero.Fs) ([]string, error)
+}
+```
+
+It is supposed to return a list of paths to config files.
+
+The default implementation uses [github.com/sagikazarmark/locafero](https://github.com/sagikazarmark/locafero) under the hood.
+
+You can supply your own implementation using `WithFinder`:
+
+```go
+v := viper.NewWithOptions(
+    viper.WithFinder(&MyFinder{}),
+)
+```
+
+For more information, check out the [Finder examples](https://pkg.go.dev/github.com/spf13/viper#Finder)
+and the [documentation](https://pkg.go.dev/github.com/sagikazarmark/locafero) for the locafero package.
+
+### New encoding API
+
+Viper now allows customizing the encoding layer by providing an API for encoding and decoding configuration data:
+
+```go
+// Encoder encodes Viper's internal data structures into a byte representation.
+// It's primarily used for encoding a map[string]any into a file format.
+type Encoder interface {
+	Encode(v map[string]any) ([]byte, error)
+}
+
+// Decoder decodes the contents of a byte slice into Viper's internal data structures.
+// It's primarily used for decoding contents of a file into a map[string]any.
+type Decoder interface {
+	Decode(b []byte, v map[string]any) error
+}
+
+// Codec combines [Encoder] and [Decoder] interfaces.
+type Codec interface {
+	Encoder
+	Decoder
+}
+```
+
+By default, Viper includes the following codecs:
+
+- JSON
+- TOML
+- YAML
+- Dotenv
+
+The rest of the codecs are moved to [github.com/go-viper/encoding](https://github.com/go-viper/encoding)
+
+Customizing the encoding layer is possible by providing a custom registry of codecs:
+
+- [Encoder](https://pkg.go.dev/github.com/spf13/viper#Encoder) -> [EncoderRegistry](https://pkg.go.dev/github.com/spf13/viper#EncoderRegistry)
+- [Decoder](https://pkg.go.dev/github.com/spf13/viper#Decoder) -> [DecoderRegistry](https://pkg.go.dev/github.com/spf13/viper#DecoderRegistry)
+- [Codec](https://pkg.go.dev/github.com/spf13/viper#Codec) -> [CodecRegistry](https://pkg.go.dev/github.com/spf13/viper#CodecRegistry)
+
+You can supply the registry of codecs to Viper using the appropriate `With*Registry` function:
+
+```go
+codecRegistry := viper.NewCodecRegistry()
+
+codecRegistry.RegisterCodec("myformat", &MyCodec{})
+
+v := viper.NewWithOptions(
+    viper.WithCodecRegistry(codecRegistry),
+)
+```
+
+### BREAKING: HCL, Java properties, INI removed from core
+
+In order to reduce third-party dependencies, Viper dropped support for the following formats from the core:
+
+- HCL
+- Java properties
+- INI
+
+You can still use these formats though by importing them from [github.com/go-viper/encoding](https://github.com/go-viper/encoding):
+
+```go
+import (
+    "github.com/go-viper/encoding/hcl"
+    "github.com/go-viper/encoding/javaproperties"
+    "github.com/go-viper/encoding/ini"
+)
+
+codecRegistry := viper.NewCodecRegistry()
+
+{
+    codec := hcl.Codec{}
+
+    codecRegistry.RegisterCodec("hcl", codec)
+    codecRegistry.RegisterCodec("tfvars", codec)
+
+}
+
+{
+    codec := &javaproperties.Codec{}
+
+    codecRegistry.RegisterCodec("properties", codec)
+    codecRegistry.RegisterCodec("props", codec)
+    codecRegistry.RegisterCodec("prop", codec)
+}
+
+codecRegistry.RegisterCodec("ini", ini.Codec{})
+
+v := viper.NewWithOptions(
+    viper.WithCodecRegistry(codecRegistry),
+)
+```

viper.go

@@ -1535,27 +1535,29 @@ func (v *Viper) MergeInConfig() error {
 func ReadConfig(in io.Reader) error { return v.ReadConfig(in) }
 
 func (v *Viper) ReadConfig(in io.Reader) error {
-	if v.configType == "" {
-		return errors.New("cannot decode configuration: config type is not set")
+	config := make(map[string]any)
+
+	err := v.unmarshalReader(in, config)
+	if err != nil {
+		return err
 	}
 
-	v.config = make(map[string]any)
-	return v.unmarshalReader(in, v.config)
+	v.config = config
+
+	return nil
 }
 
 // MergeConfig merges a new configuration with an existing config.
 func MergeConfig(in io.Reader) error { return v.MergeConfig(in) }
 
 func (v *Viper) MergeConfig(in io.Reader) error {
-	if v.configType == "" {
-		return errors.New("cannot decode configuration: config type is not set")
-	}
+	config := make(map[string]any)
 
-	cfg := make(map[string]any)
-	if err := v.unmarshalReader(in, cfg); err != nil {
+	if err := v.unmarshalReader(in, config); err != nil {
 		return err
 	}
-	return v.MergeConfigMap(cfg)
+
+	return v.MergeConfigMap(config)
 }
 
 // MergeConfigMap merges the configuration from the map given with an existing config.
@@ -1662,15 +1664,21 @@ func (v *Viper) writeConfig(filename string, force bool) error {
 }
 
 func (v *Viper) unmarshalReader(in io.Reader, c map[string]any) error {
+	format := strings.ToLower(v.getConfigType())
+	if format == "" {
+		return errors.New("cannot decode configuration: unable to determine config type")
+	}
+
 	buf := new(bytes.Buffer)
 	buf.ReadFrom(in)
 
-	format := strings.ToLower(v.getConfigType())
-
+	// TODO: remove this once SupportedExts is deprecated/removed
 	if !slices.Contains(SupportedExts, format) {
 		return UnsupportedConfigError(format)
 	}
 
+	// TODO: return [UnsupportedConfigError] if the registry does not contain the format
+	// TODO: consider deprecating this error type
 	decoder, err := v.decoderRegistry.Decoder(format)
 	if err != nil {
 		return ConfigParseError{err}

viper_test.go

@@ -1542,6 +1542,14 @@ func TestReadConfig(t *testing.T) {
 	})
 }
 
+func TestReadConfigWithSetConfigFile(t *testing.T) {
+	v := New()
+	v.SetConfigFile("config.yaml") // Dummy value to infer config type from file extension
+	err := v.ReadConfig(bytes.NewBuffer(yamlMergeExampleSrc))
+	require.NoError(t, err)
+	assert.Equal(t, 45000, v.GetInt("hello.pop"))
+}
+
 func TestIsSet(t *testing.T) {
 	v := New()
 	v.SetConfigType("yaml")
@@ -2059,6 +2067,14 @@ func TestMergeConfig(t *testing.T) {
 	assert.Equal(t, "bar", v.GetString("fu"))
 }
 
+func TestMergeConfigWithSetConfigFile(t *testing.T) {
+	v := New()
+	v.SetConfigFile("config.yaml") // Dummy value to infer config type from file extension
+	err := v.MergeConfig(bytes.NewBuffer(yamlMergeExampleSrc))
+	require.NoError(t, err)
+	assert.Equal(t, 45000, v.GetInt("hello.pop"))
+}
+
 func TestMergeConfigOverrideType(t *testing.T) {
 	v := New()
 	v.SetConfigType("json")