fix:(j2t/native) panic when fieldmap is empty

Makefile

@@ -31,7 +31,7 @@ CFLAGS_avx		:= -msse -mno-sse4 -mavx -mpclmul -mno-avx2 -mstack-alignment=0 -DUS
 CFLAGS_avx2		:= -msse -mno-sse4 -mavx -mpclmul -mavx2 -mstack-alignment=0 -DUSE_AVX=1 -DUSE_AVX2=1 
 CFLAGS_sse		:= -msse -mno-sse4 -mno-avx -mno-avx2 -mpclmul
 
-CC_amd64		:= clang
+CC_amd64		:= /opt/homebrew/Cellar/llvm\@14/14.0.6/bin/clang
 ASM2ASM_amd64	:= tools/asm2asm/asm2asm.py
 
 CFLAGS			:= -mno-red-zone

conv/j2t/conv_test.go

@@ -1552,3 +1552,19 @@ func TestSimpleArgs(t *testing.T) {
 		require.Equal(t, exp, out)
 	})
 }
+
+func TestEmptyStruct(t *testing.T) {
+	desc, err := thrift.NewDescritorFromContent(context.Background(), "a/b/main.thrift", `
+struct Req {}
+
+service Svc {
+	void Method(1: Req req)
+}
+	`, nil, true)
+	require.NoError(t, err)
+	reqDesc := desc.Functions()["Method"].Request().Struct().FieldById(1).Type()
+	cv := NewBinaryConv(conv.Options{})
+	out, err := cv.Do(context.Background(), reqDesc, []byte(`{"UNKNOWN":1}`))
+	require.NoError(t, err)
+	fmt.Printf("%+v", out)
+}

conv/j2t/impl.go

@@ -125,8 +125,8 @@ func isJsonString(val string) bool {
 	if len(val) < 2 {
 		return false
 	}
-	
-	c := json.SkipBlank(val, 0) 
+
+	c := json.SkipBlank(val, 0)
 	if c < 0 {
 		return false
 	}
@@ -171,7 +171,7 @@ func (self *BinaryConv) writeStringValue(ctx context.Context, buf *[]byte, f *th
 			if err := self.doNative(ctx, rt.Str2Mem(val), f.Type(), &p.Buf, req, false); err != nil {
 				return newError(meta.ErrConvert, fmt.Sprintf("failed to convert value of field '%s'", f.Name()), err)
 			}
-		// try text encoding, see thrift.EncodeText
+			// try text encoding, see thrift.EncodeText
 		} else {
 			return newError(meta.ErrConvert, fmt.Sprintf("unsupported http-mapping encoding %v for '%s'", enc, f.Name()), nil)
 		}
@@ -181,7 +181,7 @@ BACK:
 	return nil
 }
 
-func (self *BinaryConv)writeRequestBaseToThrift(ctx context.Context, buf *[]byte, field *thrift.FieldDescriptor) error {
+func (self *BinaryConv) writeRequestBaseToThrift(ctx context.Context, buf *[]byte, field *thrift.FieldDescriptor) error {
 	var b *base.Base
 	if bobj := ctx.Value(conv.CtxKeyThriftReqBase); bobj != nil {
 		if v, ok := bobj.(*base.Base); ok && v != nil {