support sql Value and Scan for custom date type

date.go

@@ -1,6 +1,7 @@
 package pgtype
 
 import (
+	"database/sql"
 	"database/sql/driver"
 	"encoding/binary"
 	"encoding/json"
@@ -34,6 +35,14 @@ func (dst *Date) Set(src interface{}) error {
 		}
 	}
 
+	if value, ok := src.(interface{ Value() (driver.Value, error) }); ok {
+		v, err := value.Value()
+		if err != nil {
+			return fmt.Errorf("cannot get value %v for Date: %v", value, err)
+		}
+		return dst.Set(v)
+	}
+
 	switch value := src.(type) {
 	case time.Time:
 		*dst = Date{Time: value, Status: Present}
@@ -76,6 +85,24 @@ func (dst Date) Get() interface{} {
 }
 
 func (src *Date) AssignTo(dst interface{}) error {
+	if scanner, ok := dst.(sql.Scanner); ok {
+		var err error
+		switch src.Status {
+		case Present:
+			if src.InfinityModifier != None {
+				err = scanner.Scan(src.InfinityModifier.String())
+			} else {
+				err = scanner.Scan(src.Time)
+			}
+		case Null:
+			err = scanner.Scan(nil)
+		}
+		if err != nil {
+			return fmt.Errorf("unable assign %v to %T: %s", src, dst, err)
+		}
+		return nil
+	}
+
 	switch src.Status {
 	case Present:
 		switch v := dst.(type) {

date_array_test.go

@@ -65,6 +65,14 @@ func TestDateArraySet(t *testing.T) {
 				Dimensions: []pgtype.ArrayDimension{{LowerBound: 1, Length: 1}},
 				Status:     pgtype.Present},
 		},
+		{
+			source: []customDate{{t: time.Date(2015, 2, 1, 0, 0, 0, 0, time.UTC)}},
+			result: pgtype.DateArray{
+				Elements:   []pgtype.Date{{Time: time.Date(2015, 2, 1, 0, 0, 0, 0, time.UTC), Status: pgtype.Present}},
+				Dimensions: []pgtype.ArrayDimension{{LowerBound: 1, Length: 1}},
+				Status:     pgtype.Present,
+			},
+		},
 		{
 			source: (([]time.Time)(nil)),
 			result: pgtype.DateArray{Status: pgtype.Null},
@@ -162,6 +170,7 @@ func TestDateArrayAssignTo(t *testing.T) {
 	var timeSliceDim4 [][][][]time.Time
 	var timeArrayDim2 [2][1]time.Time
 	var timeArrayDim4 [2][1][1][3]time.Time
+	var customDateSlice []customDate
 
 	simpleTests := []struct {
 		src      pgtype.DateArray
@@ -177,6 +186,15 @@ func TestDateArrayAssignTo(t *testing.T) {
 			dst:      &timeSlice,
 			expected: []time.Time{time.Date(2015, 2, 1, 0, 0, 0, 0, time.UTC)},
 		},
+		{
+			src: pgtype.DateArray{
+				Elements:   []pgtype.Date{{Time: time.Date(2015, 2, 1, 0, 0, 0, 0, time.UTC), Status: pgtype.Present}},
+				Dimensions: []pgtype.ArrayDimension{{LowerBound: 1, Length: 1}},
+				Status:     pgtype.Present,
+			},
+			dst:      &customDateSlice,
+			expected: []customDate{{t: time.Date(2015, 2, 1, 0, 0, 0, 0, time.UTC)}},
+		},
 		{
 			src:      pgtype.DateArray{Status: pgtype.Null},
 			dst:      &timeSlice,

date_test.go

@@ -1,6 +1,8 @@
 package pgtype_test
 
 import (
+	"database/sql/driver"
+	"fmt"
 	"reflect"
 	"testing"
 	"time"
@@ -9,6 +11,37 @@ import (
 	"github.com/jackc/pgtype/testutil"
 )
 
+type customDate struct {
+	t time.Time
+}
+
+func (d customDate) Value() (driver.Value, error) {
+	return d.t.Format("2006-01-02"), nil
+}
+
+func (d *customDate) Scan(src interface{}) (err error) {
+	if src == nil {
+		d.t = time.Time{}
+		return nil
+	}
+
+	switch v := src.(type) {
+	case int64:
+		d.t = time.Unix(v, 0).UTC()
+	case float64:
+		d.t = time.Unix(int64(v), 0).UTC()
+	case string:
+		d.t, err = time.Parse("2006-01-02", v)
+	case []byte:
+		d.t, err = time.Parse("2006-01-02", string(v))
+	case time.Time:
+		d.t = v
+	default:
+		err = fmt.Errorf("failed to scan type '%T' into date", src)
+	}
+	return err
+}
+
 func TestDateTranscode(t *testing.T) {
 	testutil.TestSuccessfulTranscodeEqFunc(t, "date", []interface{}{
 		&pgtype.Date{Time: time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC), Status: pgtype.Present},
@@ -43,6 +76,7 @@ func TestDateSet(t *testing.T) {
 		{source: time.Date(2200, 1, 1, 0, 0, 0, 0, time.UTC), result: pgtype.Date{Time: time.Date(2200, 1, 1, 0, 0, 0, 0, time.UTC), Status: pgtype.Present}},
 		{source: _time(time.Date(1970, 1, 1, 0, 0, 0, 0, time.UTC)), result: pgtype.Date{Time: time.Date(1970, 1, 1, 0, 0, 0, 0, time.UTC), Status: pgtype.Present}},
 		{source: "1999-12-31", result: pgtype.Date{Time: time.Date(1999, 12, 31, 0, 0, 0, 0, time.UTC), Status: pgtype.Present}},
+		{source: customDate{t: time.Date(1970, 1, 1, 0, 0, 0, 0, time.UTC)}, result: pgtype.Date{Time: time.Date(1970, 1, 1, 0, 0, 0, 0, time.UTC), Status: pgtype.Present}},
 	}
 
 	for i, tt := range successfulTests {
@@ -68,6 +102,7 @@ func TestDateAssignTo(t *testing.T) {
 		expected interface{}
 	}{
 		{src: pgtype.Date{Time: time.Date(2015, 1, 1, 0, 0, 0, 0, time.Local), Status: pgtype.Present}, dst: &tim, expected: time.Date(2015, 1, 1, 0, 0, 0, 0, time.Local)},
+		{src: pgtype.Date{Time: time.Date(2015, 1, 1, 0, 0, 0, 0, time.Local), Status: pgtype.Present}, dst: &customDate{}, expected: customDate{t: time.Date(2015, 1, 1, 0, 0, 0, 0, time.Local)}},
 		{src: pgtype.Date{Time: time.Time{}, Status: pgtype.Null}, dst: &ptim, expected: ((*time.Time)(nil))},
 	}