NilAsEmpty, nil slice=>[], golang/go#37711

bingoohuang · May 4, 2022 · 0b0090d · 0b0090d
1 parent 43c9021
commit 0b0090d
Show file tree

Hide file tree

Showing 5 changed files with 44 additions and 13 deletions.
diff --git a/pkg/jsoni/config.go b/pkg/jsoni/config.go
@@ -30,6 +30,7 @@ type Config struct {
 	ObjectFieldMustBeSimpleString bool
 	CaseSensitive                 bool
 	Int64AsString                 bool
+	NilAsEmpty                    bool
 }
 
 // API the public interface of this package.
@@ -95,6 +96,7 @@ type frozenConfig struct {
 	iteratorPool                  *sync.Pool
 	caseSensitive                 bool
 	int64AsString                 bool
+	nilAsEmpty                    bool
 
 	typeDecoders  map[string]ValDecoder
 	fieldDecoders map[string]ValDecoder
@@ -155,6 +157,7 @@ func (c Config) Froze() API {
 		disallowUnknownFields:         c.DisallowUnknownFields,
 		caseSensitive:                 c.CaseSensitive,
 		int64AsString:                 c.Int64AsString,
+		nilAsEmpty:                    c.NilAsEmpty,
 
 		typeDecoders:  map[string]ValDecoder{},
 		fieldDecoders: map[string]ValDecoder{},

diff --git a/pkg/jsoni/jsoni_test.go b/pkg/jsoni/jsoni_test.go
@@ -106,6 +106,15 @@ func TestContext(t *testing.T) {
 	assert.Equal(t, expect, m)
 }
 
+func TestMarshalJSONArray(t *testing.T) {
+	f := struct {
+		Foo []json.Number `json:",nilasempty"`
+	}{}
+
+	s, _ := jsoni.MarshalToString(f)
+	assert.Equal(t, `{"Foo":[]}`, s)
+}
+
 func TestMarshalJSON(t *testing.T) {
 	f := struct {
 		Foo json.Number

diff --git a/pkg/jsoni/reflect_extension.go b/pkg/jsoni/reflect_extension.go
@@ -370,8 +370,10 @@ func describeStruct(ctx *ctx, typ reflect2.Type) *StructDescriptor {
 				structDescriptor := describeStruct(ctx, field.Type())
 				for _, b := range structDescriptor.Fields {
 					b.levels = append([]int{i}, b.levels...)
-					omitempty := b.Encoder.(*structFieldEncoder).omitempty
-					b.Encoder = &structFieldEncoder{field: field, fieldEncoder: b.Encoder, omitempty: omitempty}
+					fieldEncoder := b.Encoder.(*structFieldEncoder)
+					omitempty := fieldEncoder.omitempty
+					nilAsEmpty := fieldEncoder.nilAsEmpty
+					b.Encoder = &structFieldEncoder{field: field, fieldEncoder: b.Encoder, omitempty: omitempty, nilAsEmpty: nilAsEmpty}
 					b.Decoder = &structFieldDecoder{field: field, fieldDecoder: b.Decoder}
 					embeddedBindings = append(embeddedBindings, b)
 				}
@@ -382,9 +384,11 @@ func describeStruct(ctx *ctx, typ reflect2.Type) *StructDescriptor {
 					structDescriptor := describeStruct(ctx, ptrType.Elem())
 					for _, b := range structDescriptor.Fields {
 						b.levels = append([]int{i}, b.levels...)
-						omitempty := b.Encoder.(*structFieldEncoder).omitempty
+						fieldEncoder := b.Encoder.(*structFieldEncoder)
+						omitempty := fieldEncoder.omitempty
+						nilAsEmpty := fieldEncoder.nilAsEmpty
 						b.Encoder = &dereferenceEncoder{ValueEncoder: b.Encoder}
-						b.Encoder = &structFieldEncoder{field: field, fieldEncoder: b.Encoder, omitempty: omitempty}
+						b.Encoder = &structFieldEncoder{field: field, fieldEncoder: b.Encoder, omitempty: omitempty, nilAsEmpty: nilAsEmpty}
 						b.Decoder = &dereferenceDecoder{valueType: ptrType.Elem(), valueDecoder: b.Decoder}
 						b.Decoder = &structFieldDecoder{field: field, fieldDecoder: b.Decoder}
 						embeddedBindings = append(embeddedBindings, b)
@@ -445,9 +449,12 @@ func (b sortableBindings) Less(i, j int) bool {
 func processTags(structDescriptor *StructDescriptor, cfg *frozenConfig) {
 	for _, b := range structDescriptor.Fields {
 		shouldOmitEmpty := cfg.omitEmptyStructField
+		nilAsEmpty := cfg.nilAsEmpty
 		tagParts := strings.Split(b.Field.Tag().Get(cfg.getTagKey()), ",")
 		for _, tagPart := range tagParts[1:] {
 			switch tagPart {
+			case "nilasempty":
+				nilAsEmpty = true
 			case "omitempty":
 				shouldOmitEmpty = true
 			case "string":
@@ -466,7 +473,7 @@ func processTags(structDescriptor *StructDescriptor, cfg *frozenConfig) {
 			}
 		}
 		b.Decoder = &structFieldDecoder{field: b.Field, fieldDecoder: b.Decoder}
-		b.Encoder = &structFieldEncoder{field: b.Field, fieldEncoder: b.Encoder, omitempty: shouldOmitEmpty}
+		b.Encoder = &structFieldEncoder{field: b.Field, fieldEncoder: b.Encoder, omitempty: shouldOmitEmpty, nilAsEmpty: nilAsEmpty}
 	}
 }
 

diff --git a/pkg/jsoni/reflect_slice.go b/pkg/jsoni/reflect_slice.go
@@ -11,23 +11,28 @@ import (
 func decoderOfSlice(ctx *ctx, typ reflect2.Type) ValDecoder {
 	sliceType := typ.(*reflect2.UnsafeSliceType)
 	decoder := decoderOfType(ctx.append("[sliceElem]"), sliceType.Elem())
-	return &sliceDecoder{sliceType, decoder}
+	return &sliceDecoder{sliceType: sliceType, elemDecoder: decoder}
 }
 
 func encoderOfSlice(ctx *ctx, typ reflect2.Type) ValEncoder {
 	sliceType := typ.(*reflect2.UnsafeSliceType)
 	encoder := encoderOfType(ctx.append("[sliceElem]"), sliceType.Elem())
-	return &sliceEncoder{sliceType, encoder}
+	return &sliceEncoder{ctx: ctx, sliceType: sliceType, elemEncoder: encoder}
 }
 
 type sliceEncoder struct {
+	ctx         *ctx
 	sliceType   *reflect2.UnsafeSliceType
 	elemEncoder ValEncoder
 }
 
 func (e *sliceEncoder) Encode(ctx context.Context, ptr unsafe.Pointer, stream *Stream) {
 	if e.sliceType.UnsafeIsNil(ptr) {
-		stream.WriteNil()
+		if e.ctx.nilAsEmpty {
+			stream.WriteEmptyArray()
+		} else {
+			stream.WriteNil()
+		}
 		return
 	}
 	length := e.sliceType.UnsafeLengthOf(ptr)

diff --git a/pkg/jsoni/reflect_struct_encoder.go b/pkg/jsoni/reflect_struct_encoder.go
@@ -51,13 +51,13 @@ func createCheckIsEmpty(ctx *ctx, typ reflect2.Type) checkIsEmpty {
 
 	switch kind := typ.Kind(); kind {
 	case reflect.Interface:
-		return &dynamicEncoder{typ}
+		return &dynamicEncoder{valType: typ}
 	case reflect.Struct:
 		return &structEncoder{typ: typ}
 	case reflect.Array:
 		return &arrayEncoder{}
 	case reflect.Slice:
-		return &sliceEncoder{}
+		return &sliceEncoder{ctx: ctx}
 	case reflect.Map:
 		return encoderOfMap(ctx, typ)
 	case reflect.Ptr:
@@ -100,6 +100,7 @@ type structFieldEncoder struct {
 	field        reflect2.StructField
 	fieldEncoder ValEncoder
 	omitempty    bool
+	nilAsEmpty   bool
 }
 
 func (e *structFieldEncoder) Encode(ctx context.Context, ptr unsafe.Pointer, stream *Stream) {
@@ -142,17 +143,23 @@ func (e *structEncoder) Encode(ctx context.Context, ptr unsafe.Pointer, stream *
 	stream.WriteObjectStart()
 	isNotFirst := false
 	for _, field := range e.fields {
-		if field.encoder.omitempty && field.encoder.IsEmpty(ctx, ptr, true) {
+		fieldEncoder := field.encoder
+		if fieldEncoder.omitempty && fieldEncoder.IsEmpty(ctx, ptr, true) {
 			continue
 		}
-		if field.encoder.IsEmbeddedPtrNil(ptr) {
+		if fieldEncoder.IsEmbeddedPtrNil(ptr) {
 			continue
 		}
 		if isNotFirst {
 			stream.WriteMore()
 		}
 		stream.WriteObjectField(field.toName)
-		field.encoder.Encode(ctx, ptr, stream)
+		if fieldEncoder.nilAsEmpty && fieldEncoder.IsEmpty(ctx, ptr, true) && fieldEncoder.field.Type().Kind() == reflect.Slice {
+			stream.WriteEmptyArray()
+		} else {
+			fieldEncoder.Encode(ctx, ptr, stream)
+		}
+
 		isNotFirst = true
 	}
 	stream.WriteObjectEnd()