fix: fixed an issue that could not set the correct NextField for fields in the embedded structure (#438)

fix #391

encode_test.go

@@ -2630,6 +2630,40 @@ func TestCustomMarshalForMapKey(t *testing.T) {
 	assertEq(t, "custom map key", string(expected), string(got))
 }
 
+func TestIssue391(t *testing.T) {
+	type A struct {
+		X string `json:"x,omitempty"`
+	}
+	type B struct {
+		A
+	}
+	type C struct {
+		X []int `json:"x,omitempty"`
+	}
+	for _, tc := range []struct {
+		name string
+		in   interface{}
+		out  string
+	}{
+		{in: struct{ B }{}, out: "{}"},
+		{in: struct {
+			B
+			Y string `json:"y"`
+		}{}, out: `{"y":""}`},
+		{in: struct {
+			Y string `json:"y"`
+			B
+		}{}, out: `{"y":""}`},
+		{in: struct{ C }{}, out: "{}"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			b, err := json.Marshal(tc.in)
+			assertErr(t, err)
+			assertEq(t, "unexpected result", tc.out, string(b))
+		})
+	}
+}
+
 func TestIssue417(t *testing.T) {
 	x := map[string]string{
 		"b": "b",

internal/encoder/code.go

@@ -397,7 +397,10 @@ func (c *StructCode) lastFieldCode(field *StructFieldCode, firstField *Opcode) *
 func (c *StructCode) lastAnonymousFieldCode(firstField *Opcode) *Opcode {
 	// firstField is special StructHead operation for anonymous structure.
 	// So, StructHead's next operation is truly struct head operation.
-	lastField := firstField.Next
+	for firstField.Op == OpStructHead {
+		firstField = firstField.Next
+	}
+	lastField := firstField
 	for lastField.NextField != nil {
 		lastField = lastField.NextField
 	}
@@ -437,11 +440,6 @@ func (c *StructCode) ToOpcode(ctx *compileContext) Opcodes {
 		}
 		if isEndField {
 			endField := fieldCodes.Last()
-			if isEmbeddedStruct(field) {
-				firstField.End = endField
-				lastField := c.lastAnonymousFieldCode(firstField)
-				lastField.NextField = endField
-			}
 			if len(codes) > 0 {
 				codes.First().End = endField
 			} else {
@@ -698,7 +696,15 @@ func (c *StructFieldCode) addStructEndCode(ctx *compileContext, codes Opcodes) O
 		Indent:     ctx.indent,
 	}
 	codes.Last().Next = end
-	codes.First().NextField = end
+	code := codes.First()
+	for code.Op == OpStructField || code.Op == OpStructHead {
+		code = code.Next
+	}
+	for code.NextField != nil {
+		code = code.NextField
+	}
+	code.NextField = end
+
 	codes = codes.Add(end)
 	ctx.incOpcodeIndex()
 	return codes