fix: add back weak string slice hook

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

README.md

@@ -802,7 +802,7 @@ if err != nil {
 }
 ```
 
-Viper uses [github.com/mitchellh/mapstructure](https://github.com/mitchellh/mapstructure) under the hood for unmarshaling values which uses `mapstructure` tags by default.
+Viper uses [github.com/go-viper/mapstructure](https://github.com/go-viper/mapstructure) under the hood for unmarshaling values which uses `mapstructure` tags by default.
 
 ### Decoding custom formats
 

go.mod

@@ -4,9 +4,9 @@ go 1.18
 
 require (
 	github.com/fsnotify/fsnotify v1.7.0
+	github.com/go-viper/mapstructure/v2 v2.0.0-alpha.1
 	github.com/hashicorp/hcl v1.0.0
 	github.com/magiconair/properties v1.8.7
-	github.com/mitchellh/mapstructure v1.5.0
 	github.com/pelletier/go-toml/v2 v2.1.1
 	github.com/sagikazarmark/crypt v0.17.0
 	github.com/sagikazarmark/locafero v0.4.0
@@ -49,6 +49,7 @@ require (
 	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/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/nats-io/nats.go v1.31.0 // indirect

go.sum

@@ -58,6 +58,8 @@ github.com/go-kit/kit v0.9.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2
 github.com/go-logfmt/logfmt v0.3.0/go.mod h1:Qt1PoO58o5twSAckw1HlFXLmHsOX5/0LbT9GBnD5lWE=
 github.com/go-logfmt/logfmt v0.4.0/go.mod h1:3RMwSq7FuexP4Kalkev3ejPJsZTpXXBr9+V4qmtdjCk=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
+github.com/go-viper/mapstructure/v2 v2.0.0-alpha.1 h1:TQcrn6Wq+sKGkpyPvppOz99zsMBaUOKXq6HSv655U1c=
+github.com/go-viper/mapstructure/v2 v2.0.0-alpha.1/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/gogo/protobuf v1.3.2 h1:Ov1cvc58UF3b5XjBnZv7+opcTcQFZebYjWzi34vdm4Q=

viper.go

@@ -34,7 +34,7 @@ import (
 	"time"
 
 	"github.com/fsnotify/fsnotify"
-	"github.com/mitchellh/mapstructure"
+	"github.com/go-viper/mapstructure/v2"
 	slog "github.com/sagikazarmark/slog-shim"
 	"github.com/spf13/afero"
 	"github.com/spf13/cast"
@@ -1158,7 +1158,8 @@ func defaultDecoderConfig(output any, opts ...DecoderConfigOption) *mapstructure
 		WeaklyTypedInput: true,
 		DecodeHook: mapstructure.ComposeDecodeHookFunc(
 			mapstructure.StringToTimeDurationHookFunc(),
-			mapstructure.StringToSliceHookFunc(","),
+			// mapstructure.StringToSliceHookFunc(","),
+			stringToWeakSliceHookFunc(","),
 		),
 	}
 	for _, opt := range opts {
@@ -1167,6 +1168,28 @@ func defaultDecoderConfig(output any, opts ...DecoderConfigOption) *mapstructure
 	return c
 }
 
+// As of mapstructure v2.0.0 StringToSliceHookFunc checks if the return type is a string slice.
+// This function removes that check.
+// TODO: implement a function that checks if the value can be converted to the return type and use it instead.
+func stringToWeakSliceHookFunc(sep string) mapstructure.DecodeHookFunc {
+	return func(
+		f reflect.Type,
+		t reflect.Type,
+		data interface{},
+	) (interface{}, error) {
+		if f.Kind() != reflect.String || t.Kind() != reflect.Slice {
+			return data, nil
+		}
+
+		raw := data.(string)
+		if raw == "" {
+			return []string{}, nil
+		}
+
+		return strings.Split(raw, sep), nil
+	}
+}
+
 // decode is a wrapper around mapstructure.Decode that mimics the WeakDecode functionality.
 func decode(input any, config *mapstructure.DecoderConfig) error {
 	decoder, err := mapstructure.NewDecoder(config)

viper_test.go

@@ -21,7 +21,7 @@ import (
 	"time"
 
 	"github.com/fsnotify/fsnotify"
-	"github.com/mitchellh/mapstructure"
+	"github.com/go-viper/mapstructure/v2"
 	"github.com/spf13/afero"
 	"github.com/spf13/cast"
 	"github.com/spf13/pflag"