fix: handle pkl sub classes / extending structs in custom classes

pkl/decode_struct.go

@@ -305,7 +305,14 @@ func getStructFields(typ reflect.Type) map[string]structField {
 		field := typ.Field(i)
 		// embedded
 		if field.Anonymous {
-			for k, v := range getStructFields(field.Type.Elem()) {
+			var fields map[string]structField
+			switch field.Type.Kind() {
+			case reflect.Ptr:
+				fields = getStructFields(field.Type.Elem())
+			case reflect.Struct:
+				fields = getStructFields(field.Type)
+			}
+			for k, v := range fields {
 				ret[k] = v
 			}
 		} else {
@@ -326,7 +333,7 @@ func (d *decoder) getOutputValue(typ reflect.Type) (*reflect.Value, error) {
 	numFields := typ.NumField()
 	for i := 0; i < numFields; i++ {
 		field := typ.Field(i)
-		if field.Anonymous {
+		if field.Anonymous && field.Type.Kind() == reflect.Ptr {
 			fieldValue := reflect.New(field.Type.Elem())
 			// Assertion: all embedded fields are pointers to structs.
 			structValue, err := d.getOutputValue(field.Type.Elem())

pkl/test_fixtures/custom/house.go

@@ -0,0 +1,17 @@
+package custom
+
+type Shape struct {
+	Area int `pkl:"area"`
+}
+
+type House struct {
+	Shape
+
+	Bedrooms int `pkl:"bedrooms"`
+
+	Bathrooms int `pkl:"bathrooms"`
+}
+
+type CustomClasses struct {
+	House *House `pkl:"house"`
+}

pkl/test_fixtures/custom/house.pkl

@@ -0,0 +1,31 @@
+// ===----------------------------------------------------------------------===//
+// Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// ===----------------------------------------------------------------------===//
+module custom
+
+house: House = new {
+  area = 2000
+  bedrooms = 3
+  bathrooms = 2
+}
+
+abstract class Shape {
+  area: Int
+}
+
+class House extends Shape {
+  bedrooms: Int
+  bathrooms: Int
+}

pkl/unmarshal_test.go

@@ -17,7 +17,10 @@ package pkl_test
 
 import (
 	"bytes"
+	"context"
 	_ "embed"
+	"github.com/apple/pkl-go/pkl/test_fixtures/custom"
+	"github.com/stretchr/testify/require"
 	"testing"
 
 	unknowntype "github.com/apple/pkl-go/pkl/test_fixtures/gen/unknown_type"
@@ -83,6 +86,9 @@ var anies []byte
 //go:embed test_fixtures/msgpack/unknown_type.pkl.msgpack
 var unknownType []byte
 
+//go:embed test_fixtures/custom/house.pkl
+var customHousePkl []byte
+
 func TestUnmarshall_Primitives(t *testing.T) {
 	var res primitives.Primitives
 	var expected = primitives.Primitives{
@@ -428,3 +434,23 @@ func TestUnmarshal_UnknownType(t *testing.T) {
 	assert.Error(t, err)
 	assert.Equal(t, "cannot decode Pkl value of type `PcfRenderer` into Go type `interface {}`. Define a custom mapping for this using `pkl.RegisterMapping`", err.Error())
 }
+
+func TestUnmarshal_Custom(t *testing.T) {
+	evaluator, err := pkl.NewEvaluator(context.Background(), pkl.PreconfiguredOptions)
+	require.NoError(t, err, "failed to create pkl evaluator")
+	defer evaluator.Close()
+
+	var res custom.CustomClasses
+	err = evaluator.EvaluateModule(context.Background(), pkl.TextSource(string(customHousePkl)), &res)
+	require.NoError(t, err, "failed to evaluate pkl module")
+
+	assert.Equal(t, custom.CustomClasses{
+		House: &custom.House{
+			Shape: custom.Shape{
+				Area: 2000,
+			},
+			Bedrooms:  3,
+			Bathrooms: 2,
+		},
+	}, res)
+}