Support for pgtype.Date JSON marshal/unmarshal.

JSON marshalling for types added on a as-needed basis.
Partly closes https://github.com/jackc/pgx/issues/310.

pgtype/date.go

@@ -3,6 +3,7 @@ package pgtype
 import (
 	"database/sql/driver"
 	"encoding/binary"
+	"encoding/json"
 	"time"
 
 	"github.com/jackc/pgx/pgio"
@@ -207,3 +208,31 @@ func (src *Date) Value() (driver.Value, error) {
 		return nil, errUndefined
 	}
 }
+
+func (src *Date) MarshalJSON() ([]byte, error) {
+	switch src.Status {
+	case Present:
+		res, err := src.Time.MarshalJSON()
+		if err != nil {
+			return nil, err
+		}
+		return res, nil
+	case Null:
+		return []byte("null"), nil
+	case Undefined:
+		return nil, errUndefined
+	}
+
+	return nil, errBadStatus
+}
+
+func (dst *Date) UnmarshalJSON(b []byte) error {
+	var n time.Time
+	if err := json.Unmarshal(b, &n); err != nil {
+		return err
+	}
+
+	*dst = Date{Time: n, Status: Present}
+
+	return nil
+}

pgtype/date_test.go

@@ -116,3 +116,30 @@ func TestDateAssignTo(t *testing.T) {
 		}
 	}
 }
+
+func TestMarshalJSON(t *testing.T) {
+	r := pgtype.Date{Time: time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC), Status: pgtype.Present}
+	enc, err := r.MarshalJSON()
+	if err != nil {
+		t.Errorf("%v", err)
+		return
+	}
+
+	if string(enc) != "\"1900-01-01T00:00:00Z\"" {
+		t.Errorf("Incorrect json marshal")
+	}
+}
+
+func TestUnmarshalJSON(t *testing.T) {
+	var r pgtype.Date
+	tm := time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC)
+
+	if err := r.UnmarshalJSON([]byte(`"` + tm.Format(time.RFC3339) + `"`)); err != nil {
+		t.Errorf("%v", err)
+		return
+	}
+
+	if tm != r.Time {
+		t.Errorf("Incorrect json unmarshal")
+	}
+}