feat(types/collections): add LegacyDec collection value (backport #21693)

CHANGELOG.md

@@ -42,6 +42,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 * (cli) [#20779](https://github.com/cosmos/cosmos-sdk/pull/20779) Added `module-hash-by-height` command to query and retrieve module hashes at a specified blockchain height, enhancing debugging capabilities.
 * (cli) [#21372](https://github.com/cosmos/cosmos-sdk/pull/21372) Added a `bulk-add-genesis-account` genesis command to add many genesis accounts at once.
+* (types/collections) [#21724](https://github.com/cosmos/cosmos-sdk/pull/21724) Added `LegacyDec` collection value.
 
 ### Improvements
 

types/collections.go

@@ -32,13 +32,20 @@ var (
 	// IntValue represents a collections.ValueCodec to work with Int.
 	IntValue collcodec.ValueCodec[math.Int] = intValueCodec{}
 
+	// LegacyDecValue represents a collections.ValueCodec to work with LegacyDec.
+	LegacyDecValue collcodec.ValueCodec[math.LegacyDec] = legacyDecValueCodec{}
+
 	// TimeKey represents a collections.KeyCodec to work with time.Time
 	// Deprecated: exists only for state compatibility reasons, should not
 	// be used for new storage keys using time. Please use the time KeyCodec
 	// provided in the collections package.
 	TimeKey collcodec.KeyCodec[time.Time] = timeKeyCodec{}
 )
 
+const (
+	LegacyDec string = "math.LegacyDec"
+)
+
 type addressUnion interface {
 	AccAddress | ValAddress | ConsAddress
 	String() string
@@ -166,6 +173,42 @@ func (i intValueCodec) ValueType() string {
 	return "math.Int"
 }
 
+type legacyDecValueCodec struct{}
+
+func (i legacyDecValueCodec) Encode(value math.LegacyDec) ([]byte, error) {
+	return value.Marshal()
+}
+
+func (i legacyDecValueCodec) Decode(b []byte) (math.LegacyDec, error) {
+	v := new(math.LegacyDec)
+	err := v.Unmarshal(b)
+	if err != nil {
+		return math.LegacyDec{}, err
+	}
+	return *v, nil
+}
+
+func (i legacyDecValueCodec) EncodeJSON(value math.LegacyDec) ([]byte, error) {
+	return value.MarshalJSON()
+}
+
+func (i legacyDecValueCodec) DecodeJSON(b []byte) (math.LegacyDec, error) {
+	v := new(math.LegacyDec)
+	err := v.UnmarshalJSON(b)
+	if err != nil {
+		return math.LegacyDec{}, err
+	}
+	return *v, nil
+}
+
+func (i legacyDecValueCodec) Stringify(value math.LegacyDec) string {
+	return value.String()
+}
+
+func (i legacyDecValueCodec) ValueType() string {
+	return LegacyDec
+}
+
 type timeKeyCodec struct{}
 
 func (timeKeyCodec) Encode(buffer []byte, key time.Time) (int, error) {