feat: allow map key pointer

Author: thecampagnards

decode.go

@@ -1771,6 +1771,14 @@ func (d *Decoder) decodeMap(ctx context.Context, dst reflect.Value, src ast.Node
 			mapValue.SetMapIndex(d.createDecodableValue(keyType), dstValue)
 			continue
 		}
+
+		// transform to map key pointer
+		for kt := keyType; kt.Kind() == reflect.Ptr; kt = kt.Elem() {
+			kk := reflect.New(k.Type())
+			kk.Elem().Set(k)
+			k = kk
+		}
+
 		if keyType.Kind() != k.Kind() {
 			return errors.ErrSyntax(
 				fmt.Sprintf("cannot convert %q type to %q type", k.Kind(), keyType.Kind()),

decode_test.go

@@ -181,6 +181,14 @@ func TestDecoder(t *testing.T) {
 			source: "v: +685_230",
 			value:  map[string]int{"v": 685230},
 		},
+		{
+			source: "v: +685_230",
+			value:  map[*string]int{ptr("v"): 685230},
+		},
+		{
+			source: "v: +685_230",
+			value:  map[**string]int{ptr(ptr("v")): 685230},
+		},
 
 		// Bools from spec
 		{
@@ -1241,12 +1249,46 @@ c:
 			actual := fmt.Sprintf("%+v", value.Elem().Interface())
 			expect := fmt.Sprintf("%+v", test.value)
 			if actual != expect {
+				if deepMapEqual(reflect.ValueOf(test.value), value.Elem()) {
+					return
+				}
 				t.Fatalf("failed to test [%s], actual=[%s], expect=[%s]", test.source, actual, expect)
 			}
 		})
 	}
 }
 
+// deepMapEqual recursively compares two reflect.Value objects.
+// It first checks if both values are of the same kind.
+// Then it compares it by checking pointers value for keys and values.
+func deepMapEqual(v1, v2 reflect.Value) bool {
+	if v1.Kind() != v2.Kind() || v1.Kind() != reflect.Map || v1.Len() != v2.Len() {
+		return false
+	}
+	for _, k1 := range v1.MapKeys() {
+		for _, k2 := range v2.MapKeys() {
+			if fromPtr(k1) != fromPtr(k2) {
+				return false
+			}
+			if fromPtr(v1.MapIndex(k1)) != fromPtr(v2.MapIndex(k2)) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func fromPtr(v reflect.Value) any {
+	for {
+		if v.Kind() == reflect.Ptr {
+			v = v.Elem()
+			continue
+		}
+		break
+	}
+	return v.Interface()
+}
+
 func TestDecoder_Invalid(t *testing.T) {
 	tests := []struct {
 		src    string