feat: allow setting a default decode hook

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

encoding.go

@@ -58,6 +58,10 @@ type CodecRegistry interface {
 // WithEncoderRegistry sets a custom [EncoderRegistry].
 func WithEncoderRegistry(r EncoderRegistry) Option {
 	return optionFunc(func(v *Viper) {
+		if r == nil {
+			return
+		}
+
 		v.encoderRegistry = r
 	})
 }
@@ -65,6 +69,10 @@ func WithEncoderRegistry(r EncoderRegistry) Option {
 // WithDecoderRegistry sets a custom [DecoderRegistry].
 func WithDecoderRegistry(r DecoderRegistry) Option {
 	return optionFunc(func(v *Viper) {
+		if r == nil {
+			return
+		}
+
 		v.decoderRegistry = r
 	})
 }
@@ -72,6 +80,10 @@ func WithDecoderRegistry(r DecoderRegistry) Option {
 // WithCodecRegistry sets a custom [EncoderRegistry] and [DecoderRegistry].
 func WithCodecRegistry(r CodecRegistry) Option {
 	return optionFunc(func(v *Viper) {
+		if r == nil {
+			return
+		}
+
 		v.encoderRegistry = r
 		v.decoderRegistry = r
 	})

finder.go

@@ -9,6 +9,10 @@ import (
 // WithFinder sets a custom [Finder].
 func WithFinder(f Finder) Option {
 	return optionFunc(func(v *Viper) {
+		if f == nil {
+			return
+		}
+
 		v.finder = f
 	})
 }
@@ -34,6 +38,10 @@ func (c *combinedFinder) Find(fsys afero.Fs) ([]string, error) {
 	var errs []error
 
 	for _, finder := range c.finders {
+		if finder == nil {
+			continue
+		}
+
 		r, err := finder.Find(fsys)
 		if err != nil {
 			errs = append(errs, err)

remote/go.mod

@@ -6,7 +6,7 @@ replace github.com/spf13/viper => ../
 
 require (
 	github.com/sagikazarmark/crypt v0.21.0
-	github.com/spf13/viper v1.20.0-alpha.2
+	github.com/spf13/viper v1.20.0-alpha.3
 )
 
 require (
@@ -39,11 +39,9 @@ require (
 	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/hcl v1.0.0 // indirect
 	github.com/hashicorp/serf v0.10.1 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/compress v1.17.2 // indirect
-	github.com/magiconair/properties v1.8.7 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
@@ -88,6 +86,5 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240617180043-68d350f18fd4 // indirect
 	google.golang.org/grpc v1.64.0 // indirect
 	google.golang.org/protobuf v1.34.2 // indirect
-	gopkg.in/ini.v1 v1.67.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

remote/go.sum

@@ -150,8 +150,6 @@ github.com/hashicorp/go-version v1.2.1/go.mod h1:fltr4n8CU8Ke44wwGCBoEymUuxUHl09
 github.com/hashicorp/golang-lru v0.5.0/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/hashicorp/golang-lru v0.5.4 h1:YDjusn29QI/Das2iO9M0BHnIbxPeyuCHsjMW+lJfyTc=
 github.com/hashicorp/golang-lru v0.5.4/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
-github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
-github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/hashicorp/logutils v1.0.0/go.mod h1:QIAnNjmIWmVIIkWDTG1z5v++HQmx9WQRO+LraFDTW64=
 github.com/hashicorp/mdns v1.0.4/go.mod h1:mtBihi+LeNXGtG8L9dX59gAEa12BDtBQSp4v/YAJqrc=
 github.com/hashicorp/memberlist v0.5.0 h1:EtYPN8DpAURiapus508I4n9CzHs2W+8NZGbmmR/prTM=
@@ -176,8 +174,6 @@ github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
-github.com/magiconair/properties v1.8.7 h1:IeQXZAiQcpL9mgcAe1Nu6cX9LLw6ExEHKjN0VQdvPDY=
-github.com/magiconair/properties v1.8.7/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-colorable v0.1.4/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
 github.com/mattn/go-colorable v0.1.6/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
@@ -449,8 +445,6 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
-gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

viper.go

@@ -183,6 +183,8 @@ type Viper struct {
 	encoderRegistry EncoderRegistry
 	decoderRegistry DecoderRegistry
 
+	decodeHook mapstructure.DecodeHookFunc
+
 	experimentalFinder     bool
 	experimentalBindStruct bool
 }
@@ -247,10 +249,25 @@ type StringReplacer interface {
 // EnvKeyReplacer sets a replacer used for mapping environment variables to internal keys.
 func EnvKeyReplacer(r StringReplacer) Option {
 	return optionFunc(func(v *Viper) {
+		if r == nil {
+			return
+		}
+
 		v.envKeyReplacer = r
 	})
 }
 
+// WithDecodeHook sets a default decode hook for mapstructure.
+func WithDecodeHook(h mapstructure.DecodeHookFunc) Option {
+	return optionFunc(func(v *Viper) {
+		if h == nil {
+			return
+		}
+
+		v.decodeHook = h
+	})
+}
+
 // NewWithOptions creates a new Viper instance.
 func NewWithOptions(opts ...Option) *Viper {
 	v := New()
@@ -896,7 +913,7 @@ func UnmarshalKey(key string, rawVal any, opts ...DecoderConfigOption) error {
 }
 
 func (v *Viper) UnmarshalKey(key string, rawVal any, opts ...DecoderConfigOption) error {
-	return decode(v.Get(key), defaultDecoderConfig(rawVal, opts...))
+	return decode(v.Get(key), v.defaultDecoderConfig(rawVal, opts...))
 }
 
 // Unmarshal unmarshals the config into a Struct. Make sure that the tags
@@ -919,13 +936,13 @@ func (v *Viper) Unmarshal(rawVal any, opts ...DecoderConfigOption) error {
 	}
 
 	// TODO: struct keys should be enough?
-	return decode(v.getSettings(keys), defaultDecoderConfig(rawVal, opts...))
+	return decode(v.getSettings(keys), v.defaultDecoderConfig(rawVal, opts...))
 }
 
 func (v *Viper) decodeStructKeys(input any, opts ...DecoderConfigOption) ([]string, error) {
 	var structKeyMap map[string]any
 
-	err := decode(input, defaultDecoderConfig(&structKeyMap, opts...))
+	err := decode(input, v.defaultDecoderConfig(&structKeyMap, opts...))
 	if err != nil {
 		return nil, err
 	}
@@ -942,20 +959,29 @@ func (v *Viper) decodeStructKeys(input any, opts ...DecoderConfigOption) ([]stri
 
 // defaultDecoderConfig returns default mapstructure.DecoderConfig with support
 // of time.Duration values & string slices.
-func defaultDecoderConfig(output any, opts ...DecoderConfigOption) *mapstructure.DecoderConfig {
-	c := &mapstructure.DecoderConfig{
-		Metadata:         nil,
-		Result:           output,
-		WeaklyTypedInput: true,
-		DecodeHook: mapstructure.ComposeDecodeHookFunc(
+func (v *Viper) defaultDecoderConfig(output any, opts ...DecoderConfigOption) *mapstructure.DecoderConfig {
+	decodeHook := v.decodeHook
+	if decodeHook == nil {
+		decodeHook = mapstructure.ComposeDecodeHookFunc(
 			mapstructure.StringToTimeDurationHookFunc(),
 			// mapstructure.StringToSliceHookFunc(","),
 			stringToWeakSliceHookFunc(","),
-		),
+		)
 	}
+
+	c := &mapstructure.DecoderConfig{
+		Metadata:         nil,
+		WeaklyTypedInput: true,
+		DecodeHook:       decodeHook,
+	}
+
 	for _, opt := range opts {
 		opt(c)
 	}
+
+	// Do not allow overwriting the output
+	c.Result = output
+
 	return c
 }
 
@@ -997,7 +1023,7 @@ func UnmarshalExact(rawVal any, opts ...DecoderConfigOption) error {
 }
 
 func (v *Viper) UnmarshalExact(rawVal any, opts ...DecoderConfigOption) error {
-	config := defaultDecoderConfig(rawVal, opts...)
+	config := v.defaultDecoderConfig(rawVal, opts...)
 	config.ErrorUnused = true
 
 	keys := v.AllKeys()

viper_test.go

@@ -894,6 +894,41 @@ func TestUnmarshal(t *testing.T) {
 	)
 }
 
+func TestUnmarshalWithDefaultDecodeHook(t *testing.T) {
+	opt := mapstructure.ComposeDecodeHookFunc(
+		mapstructure.StringToTimeDurationHookFunc(),
+		mapstructure.StringToSliceHookFunc(","),
+		// Custom Decode Hook Function
+		func(rf reflect.Kind, rt reflect.Kind, data any) (any, error) {
+			if rf != reflect.String || rt != reflect.Map {
+				return data, nil
+			}
+			m := map[string]string{}
+			raw := data.(string)
+			if raw == "" {
+				return m, nil
+			}
+			err := json.Unmarshal([]byte(raw), &m)
+			return m, err
+		},
+	)
+
+	v := NewWithOptions(WithDecodeHook(opt))
+	v.Set("credentials", "{\"foo\":\"bar\"}")
+
+	type config struct {
+		Credentials map[string]string
+	}
+
+	var C config
+
+	require.NoError(t, v.Unmarshal(&C), "unable to decode into struct")
+
+	assert.Equal(t, &config{
+		Credentials: map[string]string{"foo": "bar"},
+	}, &C)
+}
+
 func TestUnmarshalWithDecoderOptions(t *testing.T) {
 	v := New()
 	v.Set("credentials", "{\"foo\":\"bar\"}")