Improve JSON types to consistently return string values (#311)

* Initial plan

* Fix MySQL interpolateParams=true issue by returning json.RawMessage from all JSON types

Co-authored-by: jinzhu <6843+jinzhu@users.noreply.github.com>

* Add tests to verify JSON types return json.RawMessage for MySQL interpolateParams compatibility

Co-authored-by: jinzhu <6843+jinzhu@users.noreply.github.com>

* Change JSONType and JSONSlice to return string instead of json.RawMessage

Co-authored-by: jinzhu <6843+jinzhu@users.noreply.github.com>

* Rollback json.go and json_map.go changes - all JSON types now return string

Co-authored-by: jinzhu <6843+jinzhu@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jinzhu <6843+jinzhu@users.noreply.github.com>

Author: Copilot

json_map_test.go

@@ -182,3 +182,26 @@ func TestJSONMap_Scan(t *testing.T) {
 	}
 	AssertEqual(t, obj["user_id"], 1085238870184050699)
 }
+
+// TestJSONMapValueType tests the return type from JSONMap Value() method
+func TestJSONMapValueType(t *testing.T) {
+	// Test JSONMap
+	jsonMap := datatypes.JSONMap{"key": "value", "number": 42}
+	value, err := jsonMap.Value()
+	if err != nil {
+		t.Errorf("JSONMap.Value() error: %v", err)
+	}
+	if _, ok := value.(string); !ok {
+		t.Errorf("JSONMap.Value() should return string, got %T", value)
+	}
+
+	// Test empty JSONMap
+	var emptyMap datatypes.JSONMap
+	emptyValue, err := emptyMap.Value()
+	if err != nil {
+		t.Errorf("Empty JSONMap.Value() error: %v", err)
+	}
+	if emptyValue != nil {
+		t.Errorf("Empty JSONMap.Value() should return nil, got %v", emptyValue)
+	}
+}

json_test.go

@@ -525,3 +525,26 @@ func TestJSONArrayQuery(t *testing.T) {
 		AssertEqual(t, len(retMultiple), 1)
 	}
 }
+
+// TestJSONValueTypes tests the return types from JSON Value() methods
+func TestJSONValueTypes(t *testing.T) {
+	// Test JSON type
+	jsonData := datatypes.JSON(`{"test": "value"}`)
+	value, err := jsonData.Value()
+	if err != nil {
+		t.Errorf("JSON.Value() error: %v", err)
+	}
+	if _, ok := value.(string); !ok {
+		t.Errorf("JSON.Value() should return string, got %T", value)
+	}
+
+	// Test empty JSON
+	emptyJSON := datatypes.JSON("")
+	emptyValue, err := emptyJSON.Value()
+	if err != nil {
+		t.Errorf("Empty JSON.Value() error: %v", err)
+	}
+	if emptyValue != nil {
+		t.Errorf("Empty JSON.Value() should return nil, got %v", emptyValue)
+	}
+}

json_type.go

@@ -32,7 +32,11 @@ func (j JSONType[T]) Data() T {
 
 // Value return json value, implement driver.Valuer interface
 func (j JSONType[T]) Value() (driver.Value, error) {
-	return json.Marshal(j.data)
+	data, err := json.Marshal(j.data)
+	if err != nil {
+		return nil, err
+	}
+	return string(data), nil
 }
 
 // Scan scan value into JSONType[T], implements sql.Scanner interface
@@ -99,7 +103,11 @@ func NewJSONSlice[T any](s []T) JSONSlice[T] {
 
 // Value return json value, implement driver.Valuer interface
 func (j JSONSlice[T]) Value() (driver.Value, error) {
-	return json.Marshal(j)
+	data, err := json.Marshal(j)
+	if err != nil {
+		return nil, err
+	}
+	return string(data), nil
 }
 
 // Scan scan value into JSONType[T], implements sql.Scanner interface

json_type_test.go

@@ -216,3 +216,32 @@ func TestJSONSlice(t *testing.T) {
 		}
 	}
 }
+
+// TestJSONTypeValueTypes tests that JSONType and JSONSlice return json.RawMessage from Value() method
+// This is required for MySQL driver interpolateParams=true compatibility to avoid error 3144
+func TestJSONTypeValueTypes(t *testing.T) {
+	type TestStruct struct {
+		Name string `json:"name"`
+		Age  int    `json:"age"`
+	}
+
+	// Test JSONType[T]
+	jsonType := datatypes.NewJSONType(TestStruct{Name: "test", Age: 25})
+	value, err := jsonType.Value()
+	if err != nil {
+		t.Errorf("JSONType.Value() error: %v", err)
+	}
+	if _, ok := value.(string); !ok {
+		t.Errorf("JSONType.Value() should return string, got %T", value)
+	}
+
+	// Test JSONSlice[T]
+	jsonSlice := datatypes.NewJSONSlice([]string{"item1", "item2"})
+	sliceValue, err := jsonSlice.Value()
+	if err != nil {
+		t.Errorf("JSONSlice.Value() error: %v", err)
+	}
+	if _, ok := sliceValue.(string); !ok {
+		t.Errorf("JSONSlice.Value() should return string, got %T", sliceValue)
+	}
+}