Merge pull request #224 from golanglemonade/omitempty

Respect the `omitempty` flag on structs when the field value is empty

clientv2/client.go

@@ -504,9 +504,10 @@ func encodeString(v reflect.Value) ([]byte, error) {
 }
 
 type fieldInfo struct {
-	name     string
-	jsonName string
-	typ      reflect.Type
+	name      string
+	jsonName  string
+	omitempty bool
+	typ       reflect.Type
 }
 
 func prepareFields(t reflect.Type) []fieldInfo {
@@ -521,16 +522,24 @@ func prepareFields(t reflect.Type) []fieldInfo {
 		if jsonTag == "-" {
 			continue // Skip fields explicitly marked to be ignored
 		}
+
 		jsonName := f.Name
 		if jsonTag != "" {
 			parts := strings.Split(jsonTag, ",")
 			jsonName = parts[0] // Use the name specified in the JSON tag
 		}
-		fields = append(fields, fieldInfo{
+
+		fi := fieldInfo{
 			name:     f.Name,
 			jsonName: jsonName,
 			typ:      f.Type,
-		})
+		}
+
+		if strings.Contains(jsonTag, "omitempty") {
+			fi.omitempty = true
+		}
+
+		fields = append(fields, fi)
 	}
 
 	return fields
@@ -545,6 +554,10 @@ func encodeStruct(v reflect.Value) ([]byte, error) {
 			continue // Skip invalid or nil pointers to avoid panics
 		}
 
+		if field.omitempty && fieldValue.IsZero() {
+			continue // Skip nil fields marked with omitempty
+		}
+
 		encodedValue, err := encode(fieldValue)
 		if err != nil {
 			return nil, err

clientv2/client_test.go

@@ -578,6 +578,13 @@ func TestMarshalJSON(t *testing.T) {
 		Name   string `json:"name"`
 		Number Number `json:"number"`
 	}
+
+	// example with omitted fields
+	type Input struct {
+		ID   string   `json:"id"`
+		Tags []string `json:"tags,omitempty"`
+	}
+
 	testDate := time.Date(2021, 1, 1, 0, 0, 0, 0, time.UTC)
 	type args struct {
 		v any
@@ -642,6 +649,37 @@ func TestMarshalJSON(t *testing.T) {
 			},
 			want: []byte(`{"time":"2021-01-01T00:00:00Z"}`),
 		},
+		{
+			name: "marshal omitted fields",
+			args: args{
+				v: Request{
+					OperationName: "query",
+					Query:         `query ($input: Number!) { input }`,
+					Variables: map[string]any{
+						"input": Input{
+							ID: "1",
+						},
+					},
+				},
+			},
+			want: []byte(`{"operationName":"query", "query":"query ($input: Number!) { input }","variables":{"input":{"id":"1"}}}`),
+		},
+		{
+			name: "marshal fields",
+			args: args{
+				v: Request{
+					OperationName: "query",
+					Query:         `query ($input: Number!) { input }`,
+					Variables: map[string]any{
+						"input": Input{
+							ID:   "1",
+							Tags: []string{"tag1", "tag2"},
+						},
+					},
+				},
+			},
+			want: []byte(`{"operationName":"query", "query":"query ($input: Number!) { input }","variables":{"input":{"id":"1", "tags":["tag1","tag2"]}}}`),
+		},
 		{
 			name: "marshal time.Time",
 			args: args{