Copy the value from slice to avoid the original value being modified (#…

…572)

It has code to deep copy map but not slice. This PR also copies value
for slice

CHANGELOG.md

@@ -13,6 +13,10 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - Removes the chronological order between Config.Load and Config.Watch,
   so they can be called in different goroutines (#569).
 
+### Fixed
+
+- Copy the value from slice to avoid the original value being modified (#572).
+
 ## [1.3.1] - 2024-09-09
 
 ### Added

internal/convert/converter.go

@@ -553,6 +553,7 @@ func (c Converter) convertStruct(name string, fromVal, toVal reflect.Value) erro
 }
 
 func (c Converter) convertInterface(name string, fromVal, toVal reflect.Value) error {
+	// Copy the value from map and slice to avoid the original value being modified.
 	switch fromVal.Kind() {
 	case reflect.Map:
 		if fromVal.IsNil() {
@@ -564,11 +565,21 @@ func (c Converter) convertInterface(name string, fromVal, toVal reflect.Value) e
 		toVal.Set(reflect.MakeMapWithSize(fromVal.Type(), fromVal.Len()))
 
 		return c.convertMap(name, fromVal, toVal.Elem())
+	case reflect.Slice:
+		if fromVal.IsNil() {
+			toVal.SetZero()
+
+			return nil
+		}
+
+		newSlice := reflect.MakeSlice(fromVal.Type(), fromVal.Len(), fromVal.Len())
+		reflect.Copy(newSlice, fromVal)
+		toVal.Set(newSlice)
 	default:
 		toVal.Set(fromVal)
-
-		return nil
 	}
+
+	return nil
 }
 
 func pointer(val reflect.Value) reflect.Value {

internal/convert/converter_test.go

@@ -839,15 +839,15 @@ func TestConverter(t *testing.T) { //nolint:maintidx
 				"Enum":           "sky",
 				"OuterField":     "outer",
 				"PrivateField":   "private",
-				"InterfaceField": "interface{}",
+				"InterfaceField": "any",
 				"InnerField":     "squash",
 				"Inner":          map[string]any{"InnerField": "inner"},
 			},
 			to: pointer(OuterStruct{}),
 			expected: pointer(OuterStruct{
 				Enum:           Sky,
 				OuterField:     "outer",
-				InterfaceField: "interface{}",
+				InterfaceField: "any",
 				InnerStruct:    InnerStruct{InnerField: "squash"},
 				Inner:          &InnerStruct{InnerField: "inner"},
 			}),
@@ -857,18 +857,18 @@ func TestConverter(t *testing.T) { //nolint:maintidx
 			opts: []convert.Option{
 				convert.WithKeyMapper(strings.ToLower),
 			},
-			from: map[string]string{"innerfield": "inner", "interfacefield": "interface{}"},
+			from: map[string]string{"innerfield": "inner", "interfacefield": "any"},
 			to: pointer(struct {
 				InnerField     string
-				InterfaceField interface{}
+				InterfaceField any
 			}{}),
 			expected: pointer(
 				struct {
 					InnerField     string
-					InterfaceField interface{}
+					InterfaceField any
 				}{
 					InnerField:     "inner",
-					InterfaceField: "interface{}",
+					InterfaceField: "any",
 				}),
 		},
 		{
@@ -908,6 +908,12 @@ func TestConverter(t *testing.T) { //nolint:maintidx
 			to:          pointer(any(nil)),
 			expected:    pointer(any(42)),
 		},
+		{
+			description: "zero int to interface",
+			from:        0,
+			to:          pointer(any(nil)),
+			expected:    pointer(any(0)),
+		},
 		{
 			description: "string to interface",
 			from:        "str",
@@ -936,16 +942,16 @@ func TestConverter(t *testing.T) { //nolint:maintidx
 			expected: pointer(any(map[string]int{"key": 42, "keysensitive": 43})),
 		},
 		{
-			description: "packed KV and field to map[string]interface{}",
-			from: map[string]interface{}{
+			description: "packed KV and field to map[string]any",
+			from: map[string]any{
 				"key1": maps.KeyValue{
 					Key:   "key1",
 					Value: "value1",
 				},
 				"key2": "value2",
 			},
-			to: pointer(map[string]interface{}{}),
-			expected: pointer(map[string]interface{}{
+			to: pointer(map[string]any{}),
+			expected: pointer(map[string]any{
 				"key1": "value1",
 				"key2": "value2",
 			}),
@@ -955,43 +961,47 @@ func TestConverter(t *testing.T) { //nolint:maintidx
 			opts: []convert.Option{
 				convert.WithKeyMapper(strings.ToLower),
 			},
-			from: map[string]interface{}{
+			from: map[string]any{
 				"key1": maps.KeyValue{
 					Key:   "key1",
 					Value: "value1",
 				},
 				"key2": "value2",
+				"key3": []int{1, 2},
 			},
 			to: pointer(struct {
-				Key1 interface{}
-				Key2 interface{}
+				Key1 any
+				Key2 any
+				Key3 any
 			}{}),
 			expected: pointer(struct {
-				Key1 interface{}
-				Key2 interface{}
+				Key1 any
+				Key2 any
+				Key3 any
 			}{
 				Key1: "value1",
 				Key2: "value2",
+				Key3: []int{1, 2},
 			}),
 		},
 		{
-			description: "packed KV and field to interface{}",
-			from: map[string]interface{}{
+			description: "packed KV and field to any",
+			from: map[string]any{
 				"key1": maps.KeyValue{
 					Key:   "key1",
 					Value: "value1",
 				},
 				"key2": "value2",
 			},
 			to: pointer(any(nil)),
-			expected: pointer(any(map[string]interface{}{
+			expected: pointer(any(map[string]any{
 				"key1": "value1",
 				"key2": "value2",
 			})),
 		},
 		{
-			description: "nil map to interface{}",
-			from:        map[string]interface{}(nil),
+			description: "nil map to any",
+			from:        map[string]any(nil),
 			to:          pointer(any(nil)),
 			expected:    pointer(any(nil)),
 		},
@@ -1001,6 +1011,12 @@ func TestConverter(t *testing.T) { //nolint:maintidx
 			to:          pointer(any(nil)),
 			expected:    pointer(any([]int{1, 2, 3})),
 		},
+		{
+			description: "nil slice to interface",
+			from:        []int(nil),
+			to:          pointer(any(nil)),
+			expected:    pointer(any(nil)),
+		},
 		// unsupported.
 		{
 			description: "to func (unsupported)",
@@ -1065,7 +1081,7 @@ type (
 		Enum           Enum
 		OuterField     string
 		privateField   string //nolint:unused
-		InterfaceField interface{}
+		InterfaceField any
 
 		InnerStruct `konf:",squash"`
 		Inner       *InnerStruct

internal/maps/transform.go

@@ -3,12 +3,12 @@
 
 package maps
 
-func TransformKeys(src map[string]interface{}, keyMap func(string) string, mapKeyCaseSensitive bool) {
+func TransformKeys(src map[string]any, keyMap func(string) string, mapKeyCaseSensitive bool) {
 	if src == nil || keyMap == nil {
 		return
 	}
 	for key, value := range src {
-		if m, ok := value.(map[string]interface{}); ok {
+		if m, ok := value.(map[string]any); ok {
 			TransformKeys(m, keyMap, mapKeyCaseSensitive)
 		}
 		newKey := keyMap(key)