time: clean up MarshalJSON, add RFC3339 method

encoding/xml: handle time.Time as recognized type

The long term plan is to define an interface that time.Time
can implement and that encoding/xml can call, but we are
not going to try to define that interface before Go 1.
Instead, special-case time.Time in package xml, because
it is such a fundamental type, as a stop-gap.
The eventual methods will behave this way.

Fixes #2793.

R=golang-dev, r, r, n13m3y3r
CC=golang-dev
https://golang.org/cl/5634051

src/pkg/encoding/xml/atom_test.go

@@ -4,6 +4,8 @@
 
 package xml
 
+import "time"
+
 var atomValue = &Feed{
 	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
 	Title:   "Example Feed",
@@ -24,11 +26,10 @@ var atomValue = &Feed{
 }
 
 var atomXml = `` +
-	`<feed xmlns="http://www.w3.org/2005/Atom">` +
+	`<feed xmlns="http://www.w3.org/2005/Atom" updated="2003-12-13T18:30:02Z">` +
 	`<title>Example Feed</title>` +
 	`<id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>` +
 	`<link href="http://example.org/"></link>` +
-	`<updated>2003-12-13T18:30:02Z</updated>` +
 	`<author><name>John Doe</name><uri></uri><email></email></author>` +
 	`<entry>` +
 	`<title>Atom-Powered Robots Run Amok</title>` +
@@ -40,8 +41,12 @@ var atomXml = `` +
 	`</entry>` +
 	`</feed>`
 
-func ParseTime(str string) Time {
-	return Time(str)
+func ParseTime(str string) time.Time {
+	t, err := time.Parse(time.RFC3339, str)
+	if err != nil {
+		panic(err)
+	}
+	return t
 }
 
 func NewText(text string) Text {

src/pkg/encoding/xml/marshal.go

@@ -12,6 +12,7 @@ import (
 	"reflect"
 	"strconv"
 	"strings"
+	"time"
 )
 
 const (
@@ -223,7 +224,14 @@ func (p *printer) marshalValue(val reflect.Value, finfo *fieldInfo) error {
 	return nil
 }
 
+var timeType = reflect.TypeOf(time.Time{})
+
 func (p *printer) marshalSimple(typ reflect.Type, val reflect.Value) error {
+	// Normally we don't see structs, but this can happen for an attribute.
+	if val.Type() == timeType {
+		p.WriteString(val.Interface().(time.Time).Format(time.RFC3339Nano))
+		return nil
+	}
 	switch val.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 		p.WriteString(strconv.FormatInt(val.Int(), 10))
@@ -255,6 +263,10 @@ func (p *printer) marshalSimple(typ reflect.Type, val reflect.Value) error {
 var ddBytes = []byte("--")
 
 func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
+	if val.Type() == timeType {
+		p.WriteString(val.Interface().(time.Time).Format(time.RFC3339Nano))
+		return nil
+	}
 	s := parentStack{printer: p}
 	for i := range tinfo.fields {
 		finfo := &tinfo.fields[i]

src/pkg/encoding/xml/marshal_test.go

@@ -9,6 +9,7 @@ import (
 	"strconv"
 	"strings"
 	"testing"
+	"time"
 )
 
 type DriveType int
@@ -256,6 +257,12 @@ var marshalTests = []struct {
 	{Value: &Plain{[]int{1, 2, 3}}, ExpectXML: `<Plain><V>1</V><V>2</V><V>3</V></Plain>`},
 	{Value: &Plain{[3]int{1, 2, 3}}, ExpectXML: `<Plain><V>1</V><V>2</V><V>3</V></Plain>`},
 
+	// Test time.
+	{
+		Value:     &Plain{time.Unix(1e9, 123456789).UTC()},
+		ExpectXML: `<Plain><V>2001-09-09T01:46:40.123456789Z</V></Plain>`,
+	},
+
 	// A pointer to struct{} may be used to test for an element's presence.
 	{
 		Value:     &PresenceTest{new(struct{})},

src/pkg/encoding/xml/read.go

@@ -10,6 +10,7 @@ import (
 	"reflect"
 	"strconv"
 	"strings"
+	"time"
 )
 
 // BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
@@ -270,6 +271,10 @@ func (p *Decoder) unmarshal(val reflect.Value, start *StartElement) error {
 			v.Set(reflect.ValueOf(start.Name))
 			break
 		}
+		if typ == timeType {
+			saveData = v
+			break
+		}
 
 		sv = v
 		tinfo, err = getTypeInfo(typ)
@@ -473,6 +478,14 @@ func copyValue(dst reflect.Value, src []byte) (err error) {
 			src = []byte{}
 		}
 		t.SetBytes(src)
+	case reflect.Struct:
+		if t.Type() == timeType {
+			tv, err := time.Parse(time.RFC3339, string(src))
+			if err != nil {
+				return err
+			}
+			t.Set(reflect.ValueOf(tv))
+		}
 	}
 	return nil
 }

src/pkg/encoding/xml/read_test.go

@@ -7,6 +7,7 @@ package xml
 import (
 	"reflect"
 	"testing"
+	"time"
 )
 
 // Stripped down Atom feed data structures.
@@ -24,7 +25,7 @@ func TestUnmarshalFeed(t *testing.T) {
 // hget http://codereview.appspot.com/rss/mine/rsc
 const atomFeedString = `
 <?xml version="1.0" encoding="utf-8"?>
-<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en-us"><title>Code Review - My issues</title><link href="http://codereview.appspot.com/" rel="alternate"></link><link href="http://codereview.appspot.com/rss/mine/rsc" rel="self"></link><id>http://codereview.appspot.com/</id><updated>2009-10-04T01:35:58+00:00</updated><author><name>rietveld&lt;&gt;</name></author><entry><title>rietveld: an attempt at pubsubhubbub
+<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en-us" updated="2009-10-04T01:35:58+00:00"><title>Code Review - My issues</title><link href="http://codereview.appspot.com/" rel="alternate"></link><link href="http://codereview.appspot.com/rss/mine/rsc" rel="self"></link><id>http://codereview.appspot.com/</id><author><name>rietveld&lt;&gt;</name></author><entry><title>rietveld: an attempt at pubsubhubbub
 </title><link href="http://codereview.appspot.com/126085" rel="alternate"></link><updated>2009-10-04T01:35:58+00:00</updated><author><name>email-address-removed</name></author><id>urn:md5:134d9179c41f806be79b3a5f7877d19a</id><summary type="html">
   An attempt at adding pubsubhubbub support to Rietveld.
 http://code.google.com/p/pubsubhubbub
@@ -82,7 +83,7 @@ type Feed struct {
 	Title   string    `xml:"title"`
 	Id      string    `xml:"id"`
 	Link    []Link    `xml:"link"`
-	Updated Time    `xml:"updated"`
+	Updated time.Time `xml:"updated,attr"`
 	Author  Person    `xml:"author"`
 	Entry   []Entry   `xml:"entry"`
 }
@@ -91,7 +92,7 @@ type Entry struct {
 	Title   string    `xml:"title"`
 	Id      string    `xml:"id"`
 	Link    []Link    `xml:"link"`
-	Updated Time   `xml:"updated"`
+	Updated time.Time `xml:"updated"`
 	Author  Person    `xml:"author"`
 	Summary Text      `xml:"summary"`
 }
@@ -113,8 +114,6 @@ type Text struct {
 	Body string `xml:",chardata"`
 }
 
-type Time string
-
 var atomFeed = Feed{
 	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
 	Title:   "Code Review - My issues",
@@ -123,7 +122,7 @@ var atomFeed = Feed{
 		{Rel: "self", Href: "http://codereview.appspot.com/rss/mine/rsc"},
 	},
 	Id:      "http://codereview.appspot.com/",
-	Updated: "2009-10-04T01:35:58+00:00",
+	Updated: ParseTime("2009-10-04T01:35:58+00:00"),
 	Author: Person{
 		Name:     "rietveld<>",
 		InnerXML: "<name>rietveld&lt;&gt;</name>",
@@ -134,7 +133,7 @@ var atomFeed = Feed{
 			Link: []Link{
 				{Rel: "alternate", Href: "http://codereview.appspot.com/126085"},
 			},
-			Updated: "2009-10-04T01:35:58+00:00",
+			Updated: ParseTime("2009-10-04T01:35:58+00:00"),
 			Author: Person{
 				Name:     "email-address-removed",
 				InnerXML: "<name>email-address-removed</name>",
@@ -181,7 +180,7 @@ the top of feeds.py marked NOTE(rsc).
 			Link: []Link{
 				{Rel: "alternate", Href: "http://codereview.appspot.com/124106"},
 			},
-			Updated: "2009-10-03T23:02:17+00:00",
+			Updated: ParseTime("2009-10-03T23:02:17+00:00"),
 			Author: Person{
 				Name:     "email-address-removed",
 				InnerXML: "<name>email-address-removed</name>",

src/pkg/time/format.go

@@ -27,7 +27,10 @@ const (
 // compatibility with fixed-width Unix time formats.
 //
 // A decimal point followed by one or more zeros represents a fractional
-// second. When parsing (only), the input may contain a fractional second
+// second, printed to the given number of decimal places.  A decimal point
+// followed by one or more nines represents a fractional second, printed to
+// the given number of decimal places, with trailing zeros removed.
+// When parsing (only), the input may contain a fractional second
 // field immediately after the seconds field, even if the layout does not
 // signify its presence. In that case a decimal point followed by a maximal
 // series of digits is parsed as a fractional second.
@@ -50,6 +53,7 @@ const (
 	RFC1123     = "Mon, 02 Jan 2006 15:04:05 MST"
 	RFC1123Z    = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone
 	RFC3339     = "2006-01-02T15:04:05Z07:00"
+	RFC3339Nano = "2006-01-02T15:04:05.999999999Z07:00"
 	Kitchen     = "3:04PM"
 	// Handy time stamps.
 	Stamp      = "Jan _2 15:04:05"
@@ -165,15 +169,17 @@ func nextStdChunk(layout string) (prefix, std, suffix string) {
 			if len(layout) >= i+6 && layout[i:i+6] == stdISO8601ColonTZ {
 				return layout[0:i], layout[i : i+6], layout[i+6:]
 			}
-		case '.': // .000 - multiple digits of zeros (only) for fractional seconds.
-			numZeros := 0
-			var j int
-			for j = i + 1; j < len(layout) && layout[j] == '0'; j++ {
-				numZeros++
+		case '.': // .000 or .999 - repeated digits for fractional seconds.
+			if i+1 < len(layout) && (layout[i+1] == '0' || layout[i+1] == '9') {
+				ch := layout[i+1]
+				j := i + 1
+				for j < len(layout) && layout[j] == ch {
+					j++
+				}
+				// String of digits must end here - only fractional second is all digits.
+				if !isDigit(layout, j) {
+					return layout[0:i], layout[i:j], layout[j:]
 				}
-			// String of digits must end here - only fractional second is all zeros.
-			if numZeros > 0 && !isDigit(layout, j) {
-				return layout[0:i], layout[i : i+1+numZeros], layout[i+1+numZeros:]
 			}
 		}
 	}
@@ -313,7 +319,7 @@ func pad(i int, padding string) string {
 func zeroPad(i int) string { return pad(i, "0") }
 
 // formatNano formats a fractional second, as nanoseconds.
-func formatNano(nanosec, n int) string {
+func formatNano(nanosec, n int, trim bool) string {
 	// User might give us bad data. Make sure it's positive and in range.
 	// They'll get nonsense output but it will have the right format.
 	s := itoa(int(uint(nanosec) % 1e9))
@@ -324,6 +330,14 @@ func formatNano(nanosec, n int) string {
 	if n > 9 {
 		n = 9
 	}
+	if trim {
+		for n > 0 && s[n-1] == '0' {
+			n--
+		}
+		if n == 0 {
+			return ""
+		}
+	}
 	return "." + s[:n]
 }
 
@@ -388,7 +402,24 @@ func (t Time) Format(layout string) string {
 		case stdYear:
 			p = zeroPad(year % 100)
 		case stdLongYear:
+			// Pad year to at least 4 digits.
 			p = itoa(year)
+			switch {
+			case year <= -1000:
+				// ok
+			case year <= -100:
+				p = p[:1] + "0" + p[1:]
+			case year <= -10:
+				p = p[:1] + "00" + p[1:]
+			case year < 0:
+				p = p[:1] + "000" + p[1:]
+			case year < 10:
+				p = "000" + p
+			case year < 100:
+				p = "00" + p
+			case year < 1000:
+				p = "0" + p
+			}
 		case stdMonth:
 			p = month.String()[:3]
 		case stdLongMonth:
@@ -481,8 +512,8 @@ func (t Time) Format(layout string) string {
 				p += zeroPad(zone % 60)
 			}
 		default:
-			if len(std) >= 2 && std[0:2] == ".0" {
-				p = formatNano(t.Nanosecond(), len(std)-1)
+			if len(std) >= 2 && (std[0:2] == ".0" || std[0:2] == ".9") {
+				p = formatNano(t.Nanosecond(), len(std)-1, std[1] == '9')
 			}
 		}
 		b.WriteString(p)

src/pkg/time/time.go

@@ -841,46 +841,17 @@ func (t *Time) GobDecode(buf []byte) error {
 // MarshalJSON implements the json.Marshaler interface.
 // Time is formatted as RFC3339.
 func (t Time) MarshalJSON() ([]byte, error) {
-	yearInt := t.Year()
-	if yearInt < 0 || yearInt > 9999 {
+	if y := t.Year(); y < 0 || y >= 10000 {
 		return nil, errors.New("Time.MarshalJSON: year outside of range [0,9999]")
 	}
-
-	// We need a four-digit year, but Format produces variable-width years.
-	year := itoa(yearInt)
-	year = "0000"[:4-len(year)] + year
-
-	var formattedTime string
-	if t.nsec == 0 {
-		// RFC3339, no fractional second
-		formattedTime = t.Format("-01-02T15:04:05Z07:00")
-	} else {
-		// RFC3339 with fractional second
-		formattedTime = t.Format("-01-02T15:04:05.000000000Z07:00")
-
-		// Trim trailing zeroes from fractional second.
-		const nanoEnd = 24 // Index of last digit of fractional second
-		var i int
-		for i = nanoEnd; formattedTime[i] == '0'; i-- {
-			// Seek backwards until first significant digit is found.
-		}
-
-		formattedTime = formattedTime[:i+1] + formattedTime[nanoEnd+1:]
-	}
-
-	buf := make([]byte, 0, 1+len(year)+len(formattedTime)+1)
-	buf = append(buf, '"')
-	buf = append(buf, year...)
-	buf = append(buf, formattedTime...)
-	buf = append(buf, '"')
-	return buf, nil
+	return []byte(t.Format(`"` + RFC3339Nano + `"`)), nil
 }
 
 // UnmarshalJSON implements the json.Unmarshaler interface.
 // Time is expected in RFC3339 format.
 func (t *Time) UnmarshalJSON(data []byte) (err error) {
-	*t, err = Parse("\""+RFC3339+"\"", string(data))
 	// Fractional seconds are handled implicitly by Parse.
+	*t, err = Parse(`"`+RFC3339+`"`, string(data))
 	return
 }
 

src/pkg/time/time_test.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"encoding/gob"
 	"encoding/json"
+	"fmt"
 	"math/rand"
 	"strconv"
 	"strings"
@@ -227,6 +228,7 @@ var formatTests = []FormatTest{
 	{"RFC1123", RFC1123, "Wed, 04 Feb 2009 21:00:57 PST"},
 	{"RFC1123Z", RFC1123Z, "Wed, 04 Feb 2009 21:00:57 -0800"},
 	{"RFC3339", RFC3339, "2009-02-04T21:00:57-08:00"},
+	{"RFC3339Nano", RFC3339Nano, "2009-02-04T21:00:57.0123456-08:00"},
 	{"Kitchen", Kitchen, "9:00PM"},
 	{"am/pm", "3pm", "9pm"},
 	{"AM/PM", "3PM", "9PM"},
@@ -235,12 +237,12 @@ var formatTests = []FormatTest{
 	{"Stamp", Stamp, "Feb  4 21:00:57"},
 	{"StampMilli", StampMilli, "Feb  4 21:00:57.012"},
 	{"StampMicro", StampMicro, "Feb  4 21:00:57.012345"},
-	{"StampNano", StampNano, "Feb  4 21:00:57.012345678"},
+	{"StampNano", StampNano, "Feb  4 21:00:57.012345600"},
 }
 
 func TestFormat(t *testing.T) {
-	// The numeric time represents Thu Feb  4 21:00:57.012345678 PST 2010
-	time := Unix(0, 1233810057012345678)
+	// The numeric time represents Thu Feb  4 21:00:57.012345600 PST 2010
+	time := Unix(0, 1233810057012345600)
 	for _, test := range formatTests {
 		result := time.Format(test.format)
 		if result != test.result {
@@ -249,6 +251,38 @@ func TestFormat(t *testing.T) {
 	}
 }
 
+func TestFormatShortYear(t *testing.T) {
+	years := []int{
+		-100001, -100000, -99999,
+		-10001, -10000, -9999,
+		-1001, -1000, -999,
+		-101, -100, -99,
+		-11, -10, -9,
+		-1, 0, 1,
+		9, 10, 11,
+		99, 100, 101,
+		999, 1000, 1001,
+		9999, 10000, 10001,
+		99999, 100000, 100001,
+	}
+
+	for _, y := range years {
+		time := Date(y, January, 1, 0, 0, 0, 0, UTC)
+		result := time.Format("2006.01.02")
+		var want string
+		if y < 0 {
+			// The 4 in %04d counts the - sign, so print -y instead
+			// and introduce our own - sign.
+			want = fmt.Sprintf("-%04d.%02d.%02d", -y, 1, 1)
+		} else {
+			want = fmt.Sprintf("%04d.%02d.%02d", y, 1, 1)
+		}
+		if result != want {
+			t.Errorf("(jan 1 %d).Format(\"2006.01.02\") = %q, want %q", y, result, want)
+		}
+	}
+}
+
 type ParseTest struct {
 	name       string
 	format     string
@@ -782,7 +816,7 @@ func TestTimeJSON(t *testing.T) {
 		if jsonBytes, err := json.Marshal(tt.time); err != nil {
 			t.Errorf("%v json.Marshal error = %v, want nil", tt.time, err)
 		} else if string(jsonBytes) != tt.json {
-			t.Errorf("%v JSON = %q, want %q", tt.time, string(jsonBytes), tt.json)
+			t.Errorf("%v JSON = %#q, want %#q", tt.time, string(jsonBytes), tt.json)
 		} else if err = json.Unmarshal(jsonBytes, &jsonTime); err != nil {
 			t.Errorf("%v json.Unmarshal error = %v, want nil", tt.time, err)
 		} else if !equalTimeAndZone(jsonTime, tt.time) {