Merge pull request #259 from Taik/NullJSONText

Add NullJSONText

types/types.go

@@ -57,9 +57,14 @@ func (g *GzippedText) Scan(src interface{}) error {
 // implements `Unmarshal`, which unmarshals the json within to an interface{}
 type JSONText json.RawMessage
 
-// MarshalJSON returns j as the JSON encoding of j.
-func (j JSONText) MarshalJSON() ([]byte, error) {
-	return j, nil
+var _EMPTY_JSON = JSONText("{}")
+
+// MarshalJSON returns the *j as the JSON encoding of j.
+func (j *JSONText) MarshalJSON() ([]byte, error) {
+	if len(*j) == 0 {
+		*j = _EMPTY_JSON
+	}
+	return *j, nil
 }
 
 // UnmarshalJSON sets *j to a copy of data
@@ -69,7 +74,6 @@ func (j *JSONText) UnmarshalJSON(data []byte) error {
 	}
 	*j = append((*j)[0:0], data...)
 	return nil
-
 }
 
 // Value returns j as a value.  This does a validating unmarshal into another
@@ -86,11 +90,17 @@ func (j JSONText) Value() (driver.Value, error) {
 // Scan stores the src in *j.  No validation is done.
 func (j *JSONText) Scan(src interface{}) error {
 	var source []byte
-	switch src.(type) {
+	switch t := src.(type) {
 	case string:
-		source = []byte(src.(string))
+		source = []byte(t)
 	case []byte:
-		source = src.([]byte)
+		if len(t) == 0 {
+			source = _EMPTY_JSON
+		} else {
+			source = t
+		}
+	case nil:
+		*j = _EMPTY_JSON
 	default:
 		return errors.New("Incompatible type for JSONText")
 	}
@@ -100,14 +110,43 @@ func (j *JSONText) Scan(src interface{}) error {
 
 // Unmarshal unmarshal's the json in j to v, as in json.Unmarshal.
 func (j *JSONText) Unmarshal(v interface{}) error {
+	if len(*j) == 0 {
+		*j = _EMPTY_JSON
+	}
 	return json.Unmarshal([]byte(*j), v)
 }
 
-// Pretty printing for JSONText types
+// String supports pretty printing for JSONText types.
 func (j JSONText) String() string {
 	return string(j)
 }
 
+// NullJSONText represents a JSONText that may be null.
+// NullJSONText implements the scanner interface so
+// it can be used as a scan destination, similar to NullString.
+type NullJSONText struct {
+	JSONText
+	Valid bool // Valid is true if JSONText is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (n *NullJSONText) Scan(value interface{}) error {
+	if value == nil {
+		n.JSONText, n.Valid = _EMPTY_JSON, false
+		return nil
+	}
+	n.Valid = true
+	return n.JSONText.Scan(value)
+}
+
+// Value implements the driver Valuer interface.
+func (n NullJSONText) Value() (driver.Value, error) {
+	if !n.Valid {
+		return nil, nil
+	}
+	return n.JSONText.Value()
+}
+
 // BitBool is an implementation of a bool for the MySQL type BIT(1).
 // This type allows you to avoid wasting an entire byte for MySQL's boolean type TINYINT.
 type BitBool bool

types/types_test.go

@@ -39,6 +39,59 @@ func TestJSONText(t *testing.T) {
 	if err == nil {
 		t.Errorf("Was expecting invalid json to fail!")
 	}
+
+	j = JSONText("")
+	v, err = j.Value()
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+
+	err = (&j).Scan(v)
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+
+	j = JSONText(nil)
+	v, err = j.Value()
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+
+	err = (&j).Scan(v)
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+}
+
+func TestNullJSONText(t *testing.T) {
+	j := NullJSONText{}
+	err := j.Scan(`{"foo": 1, "bar": 2}`)
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+	v, err := j.Value()
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+	err = (&j).Scan(v)
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+	m := map[string]interface{}{}
+	j.Unmarshal(&m)
+
+	if m["foo"].(float64) != 1 || m["bar"].(float64) != 2 {
+		t.Errorf("Expected valid json but got some garbage instead? %#v", m)
+	}
+
+	j = NullJSONText{}
+	err = j.Scan(nil)
+	if err != nil {
+		t.Errorf("Was not expecting an error")
+	}
+	if j.Valid != false {
+		t.Errorf("Expected valid to be false, but got true")
+	}
 }
 
 func TestBitBool(t *testing.T) {