feat: support for automatically initializing squashed pointer structs

Author: tuunit

mapstructure.go

@@ -1409,6 +1409,15 @@ func (d *Decoder) decodeStructFromMap(name string, dataVal, val reflect.Value) e
 					if !fieldVal.IsNil() {
 						structs = append(structs, fieldVal.Elem().Elem())
 					}
+				case reflect.Ptr:
+					if fieldVal.Type().Elem().Kind() == reflect.Struct {
+						if fieldVal.IsNil() {
+							fieldVal.Set(reflect.New(fieldVal.Type().Elem()))
+						}
+						structs = append(structs, fieldVal.Elem())
+					} else {
+						errs = append(errs, fmt.Errorf("%s: unsupported type for squash: %s", fieldType.Name, fieldVal.Kind()))
+					}
 				default:
 					errs = append(errs, fmt.Errorf("%s: unsupported type for squash: %s", fieldType.Name, fieldVal.Kind()))
 				}

mapstructure_test.go

@@ -878,6 +878,29 @@ func TestDecode_EmbeddedPointerSquash_FromMapToStruct(t *testing.T) {
 	}
 }
 
+func TestDecode_EmbeddedPointerSquash_WithoutPreInitializedStructs_FromMapToStruct(t *testing.T) {
+	t.Parallel()
+
+	input := map[string]interface{}{
+		"Vstring": "foo",
+		"Vunique": "bar",
+	}
+
+	result := EmbeddedPointerSquash{}
+	err := Decode(input, &result)
+	if err != nil {
+		t.Fatalf("got an err: %s", err.Error())
+	}
+
+	if result.Vstring != "foo" {
+		t.Errorf("vstring value should be 'foo': %#v", result.Vstring)
+	}
+
+	if result.Vunique != "bar" {
+		t.Errorf("vunique value should be 'bar': %#v", result.Vunique)
+	}
+}
+
 func TestDecode_EmbeddedPointerSquashWithNestedMapstructure_FromStructToMap(t *testing.T) {
 	t.Parallel()