time: fix timezone lookup logic for non-DST zones

This change fixes time.LoadLocationFromTZData and time.Location.lookup logic if the given time is after the last transition and the extend string doesn't have the DST rule.

Fixes #58682

Change-Id: Ie34a6d658d14c2b33098b29ab83c041ef0d34266
GitHub-Last-Rev: f6681eb44c0ea0772004e56eb68fcbd9023d971e
GitHub-Pull-Request: golang/go#58684
Reviewed-on: https://go-review.googlesource.com/c/go/+/471020
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>

diff --git a/src/time/time_test.go b/src/time/time_test.go
index 4221efec8872b7a385d3b92a7f403d8dd563f119..3b30f802efe776cf1592184ef5f10bf300c7808e 100644 (file)
--- a/src/time/time_test.go
+++ b/src/time/time_test.go
@@ -1860,16 +1860,26 @@ func TestZoneBounds(t *testing.T) {
                5: {Date(1991, September, 14, 17, 0, 0, 0, loc), boundTwo, boundThree},
                6: {Date(1991, September, 15, 0, 50, 0, 0, loc), boundTwo, boundThree},
 
+               // The ZoneBounds of a "Asia/Shanghai" after the last transition (Standard Time)
+               7:  {boundThree, boundThree, Time{}},
+               8:  {Date(1991, December, 15, 1, 50, 0, 0, loc), boundThree, Time{}},
+               9:  {Date(1992, April, 13, 17, 50, 0, 0, loc), boundThree, Time{}},
+               10: {Date(1992, April, 13, 18, 0, 0, 0, loc), boundThree, Time{}},
+               11: {Date(1992, April, 14, 1, 50, 0, 0, loc), boundThree, Time{}},
+               12: {Date(1992, September, 14, 16, 50, 0, 0, loc), boundThree, Time{}},
+               13: {Date(1992, September, 14, 17, 0, 0, 0, loc), boundThree, Time{}},
+               14: {Date(1992, September, 15, 0, 50, 0, 0, loc), boundThree, Time{}},
+
                // The ZoneBounds of a local time would return two local Time.
                // Note: We preloaded "America/Los_Angeles" as time.Local for testing
-               7:  {makeLocalTime(0), makeLocalTime(-5756400), makeLocalTime(9972000)},
-               8:  {makeLocalTime(1221681866), makeLocalTime(1205056800), makeLocalTime(1225616400)},
-               9:  {makeLocalTime(2152173599), makeLocalTime(2145916800), makeLocalTime(2152173600)},
-               10: {makeLocalTime(2152173600), makeLocalTime(2152173600), makeLocalTime(2172733200)},
-               11: {makeLocalTime(2152173601), makeLocalTime(2152173600), makeLocalTime(2172733200)},
-               12: {makeLocalTime(2159200800), makeLocalTime(2152173600), makeLocalTime(2172733200)},
-               13: {makeLocalTime(2172733199), makeLocalTime(2152173600), makeLocalTime(2172733200)},
-               14: {makeLocalTime(2172733200), makeLocalTime(2172733200), makeLocalTime(2177452800)},
+               15: {makeLocalTime(0), makeLocalTime(-5756400), makeLocalTime(9972000)},
+               16: {makeLocalTime(1221681866), makeLocalTime(1205056800), makeLocalTime(1225616400)},
+               17: {makeLocalTime(2152173599), makeLocalTime(2145916800), makeLocalTime(2152173600)},
+               18: {makeLocalTime(2152173600), makeLocalTime(2152173600), makeLocalTime(2172733200)},
+               19: {makeLocalTime(2152173601), makeLocalTime(2152173600), makeLocalTime(2172733200)},
+               20: {makeLocalTime(2159200800), makeLocalTime(2152173600), makeLocalTime(2172733200)},
+               21: {makeLocalTime(2172733199), makeLocalTime(2152173600), makeLocalTime(2172733200)},
+               22: {makeLocalTime(2172733200), makeLocalTime(2172733200), makeLocalTime(2177452800)},
        }
        for i, tt := range realTests {
                start, end := tt.giveTime.ZoneBounds()

diff --git a/src/time/zoneinfo.go b/src/time/zoneinfo.go
index dd3b4edd01d0b81d1424917230dad3d9c6ca8af8..4edcf3d98f12963a43378213235da740fb1c2469 100644 (file)
--- a/src/time/zoneinfo.go
+++ b/src/time/zoneinfo.go
@@ -203,7 +203,7 @@ func (l *Location) lookup(sec int64) (name string, offset int, start, end int64,
        // If we're at the end of the known zone transitions,
        // try the extend string.
        if lo == len(tx)-1 && l.extend != "" {
-               if ename, eoffset, estart, eend, eisDST, ok := tzset(l.extend, end, sec); ok {
+               if ename, eoffset, estart, eend, eisDST, ok := tzset(l.extend, start, sec); ok {
                        return ename, eoffset, estart, eend, eisDST
                }
        }
@@ -264,12 +264,12 @@ func (l *Location) firstZoneUsed() bool {
 }
 
 // tzset takes a timezone string like the one found in the TZ environment
-// variable, the end of the last time zone transition expressed as seconds
+// variable, the time of the last time zone transition expressed as seconds
 // since January 1, 1970 00:00:00 UTC, and a time expressed the same way.
 // We call this a tzset string since in C the function tzset reads TZ.
 // The return values are as for lookup, plus ok which reports whether the
 // parse succeeded.
-func tzset(s string, initEnd, sec int64) (name string, offset int, start, end int64, isDST, ok bool) {
+func tzset(s string, lastTxSec, sec int64) (name string, offset int, start, end int64, isDST, ok bool) {
        var (
                stdName, dstName     string
                stdOffset, dstOffset int
@@ -290,7 +290,7 @@ func tzset(s string, initEnd, sec int64) (name string, offset int, start, end in
 
        if len(s) == 0 || s[0] == ',' {
                // No daylight savings time.
-               return stdName, stdOffset, initEnd, omega, false, true
+               return stdName, stdOffset, lastTxSec, omega, false, true
        }
 
        dstName, s, ok = tzsetName(s)

diff --git a/src/time/zoneinfo_read.go b/src/time/zoneinfo_read.go
index d8b35003a1d6374fcdd8d43dafd1ebed29fc83b6..4d0e47d890ac305c9f8ceb19339065c07c5794ac 100644 (file)
--- a/src/time/zoneinfo_read.go
+++ b/src/time/zoneinfo_read.go
@@ -329,7 +329,7 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
                        } else if l.extend != "" {
                                // If we're at the end of the known zone transitions,
                                // try the extend string.
-                               if name, offset, estart, eend, isDST, ok := tzset(l.extend, l.cacheEnd, sec); ok {
+                               if name, offset, estart, eend, isDST, ok := tzset(l.extend, l.cacheStart, sec); ok {
                                        l.cacheStart = estart
                                        l.cacheEnd = eend
                                        // Find the zone that is returned by tzset to avoid allocation if possible.

diff --git a/src/time/zoneinfo_test.go b/src/time/zoneinfo_test.go
index 243ff8ebdee775cfaa154f5c0ae836f7dabc0cb7..8cd37b5e27fe240557568ebedac59d291b94a878 100644 (file)
--- a/src/time/zoneinfo_test.go
+++ b/src/time/zoneinfo_test.go
@@ -271,6 +271,7 @@ func TestTzset(t *testing.T) {
                {"PST8PDT,M3.2.0,M11.1.0", 0, 2172733199, "PDT", -7 * 60 * 60, 2152173600, 2172733200, true, true},
                {"PST8PDT,M3.2.0,M11.1.0", 0, 2172733200, "PST", -8 * 60 * 60, 2172733200, 2177452800, false, true},
                {"PST8PDT,M3.2.0,M11.1.0", 0, 2172733201, "PST", -8 * 60 * 60, 2172733200, 2177452800, false, true},
+               {"KST-9", 592333200, 1677246697, "KST", 9 * 60 * 60, 592333200, 1<<63 - 1, false, true},
        } {
                name, off, start, end, isDST, ok := time.Tzset(test.inStr, test.inEnd, test.inSec)
                if name != test.name || off != test.off || start != test.start || end != test.end || isDST != test.isDST || ok != test.ok {