time: fix zoneinfo.zip locating logic when built with -trimpath

When the test binary is built with the -trimpath flag,
runtime.GOROOT() is invalid, and must not be used to locate
GOROOT/lib/time/zoneinfo.zip. (We can use other sources instead.)

However, the test for the package expects zoneinfo.zip to definitely
exist. 'go test' runs the test binary in the directory containing its
source code — in this case GOROOT/src/time — so we can use that
information to find the zoneinfo.zip file when runtime.GOROOT isn't
available.

For #51483

Change-Id: I9de35252a988d146b5d746794323214d400e64e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/391814
Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/time/export_android_test.go

@@ -4,9 +4,13 @@
 
 package time
 
-func ForceAndroidTzdataForTest(tzdata bool) {
-	forceZipFileForTesting(false)
-	if tzdata {
-		zoneSources = zoneSources[:len(zoneSources)-1]
+func ForceAndroidTzdataForTest() (undo func()) {
+	allowGorootSource = false
+	origLoadFromEmbeddedTZData := loadFromEmbeddedTZData
+	loadFromEmbeddedTZData = nil
+
+	return func() {
+		allowGorootSource = true
+		loadFromEmbeddedTZData = origLoadFromEmbeddedTZData
 	}
 }

src/time/export_test.go

@@ -28,7 +28,8 @@ func ResetZoneinfoForTesting() {
 }
 
 var (
-	ForceZipFileForTesting = forceZipFileForTesting
+	DisablePlatformSources = disablePlatformSources
+	GorootZoneSource       = gorootZoneSource
 	ParseTimeZone          = parseTimeZone
 	SetMono                = (*Time).setMono
 	GetMono                = (*Time).mono

src/time/format_test.go

@@ -408,8 +408,8 @@ func TestParseInLocation(t *testing.T) {
 }
 
 func TestLoadLocationZipFile(t *testing.T) {
-	ForceZipFileForTesting(true)
-	defer ForceZipFileForTesting(false)
+	undo := DisablePlatformSources()
+	defer undo()
 
 	_, err := LoadLocation("Australia/Sydney")
 	if err != nil {

src/time/internal_test.go

@@ -5,26 +5,31 @@
 package time
 
 func init() {
-	// force US/Pacific for time zone tests
+	// Force US/Pacific for time zone tests.
 	ForceUSPacificForTesting()
 }
 
 func initTestingZone() {
-	z, err := loadLocation("America/Los_Angeles", zoneSources[len(zoneSources)-1:])
+	// For hermeticity, use only tzinfo source from the test's GOROOT,
+	// not the system sources and not whatever GOROOT may happen to be
+	// set in the process's environment (if any).
+	// This test runs in GOROOT/src/time, so GOROOT is "../..",
+	// but it is theoretically possible
+	sources := []string{"../../lib/time/zoneinfo.zip"}
+	z, err := loadLocation("America/Los_Angeles", sources)
 	if err != nil {
 		panic("cannot load America/Los_Angeles for testing: " + err.Error() + "; you may want to use -tags=timetzdata")
 	}
 	z.name = "Local"
 	localLoc = *z
 }
 
-var OrigZoneSources = zoneSources
+var origPlatformZoneSources []string = platformZoneSources
 
-func forceZipFileForTesting(zipOnly bool) {
-	zoneSources = make([]string, len(OrigZoneSources))
-	copy(zoneSources, OrigZoneSources)
-	if zipOnly {
-		zoneSources = zoneSources[len(zoneSources)-1:]
+func disablePlatformSources() (undo func()) {
+	platformZoneSources = nil
+	return func() {
+		platformZoneSources = origPlatformZoneSources
 	}
 }
 

src/time/time_test.go

@@ -1557,8 +1557,8 @@ func TestConcurrentTimerResetStop(t *testing.T) {
 }
 
 func TestTimeIsDST(t *testing.T) {
-	ForceZipFileForTesting(true)
-	defer ForceZipFileForTesting(false)
+	undo := DisablePlatformSources()
+	defer undo()
 
 	tzWithDST, err := LoadLocation("Australia/Sydney")
 	if err != nil {
@@ -1619,8 +1619,8 @@ func TestTimeAddSecOverflow(t *testing.T) {
 
 // Issue 49284: time: ParseInLocation incorrectly because of Daylight Saving Time
 func TestTimeWithZoneTransition(t *testing.T) {
-	ForceZipFileForTesting(true)
-	defer ForceZipFileForTesting(false)
+	undo := DisablePlatformSources()
+	defer undo()
 
 	loc, err := LoadLocation("Asia/Shanghai")
 	if err != nil {

src/time/tzdata_test.go

@@ -17,8 +17,8 @@ var zones = []string{
 }
 
 func TestEmbeddedTZData(t *testing.T) {
-	time.ForceZipFileForTesting(true)
-	defer time.ForceZipFileForTesting(false)
+	undo := time.DisablePlatformSources()
+	defer undo()
 
 	for _, zone := range zones {
 		ref, err := time.LoadLocation(zone)

src/time/zoneinfo.go

@@ -665,7 +665,7 @@ func LoadLocation(name string) (*Location, error) {
 			firstErr = err
 		}
 	}
-	if z, err := loadLocation(name, zoneSources); err == nil {
+	if z, err := loadLocation(name, platformZoneSources); err == nil {
 		return z, nil
 	} else if firstErr == nil {
 		firstErr = err

src/time/zoneinfo_android.go

@@ -10,14 +10,12 @@ package time
 
 import (
 	"errors"
-	"runtime"
 	"syscall"
 )
 
-var zoneSources = []string{
+var platformZoneSources = []string{
 	"/system/usr/share/zoneinfo/tzdata",
 	"/data/misc/zoneinfo/current/tzdata",
-	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
 }
 
 func initLocal() {
@@ -29,6 +27,15 @@ func init() {
 	loadTzinfoFromTzdata = androidLoadTzinfoFromTzdata
 }
 
+var allowGorootSource = true
+
+func gorootZoneSource(goroot string) (string, bool) {
+	if goroot == "" || !allowGorootSource {
+		return "", false
+	}
+	return goroot + "/lib/time/zoneinfo.zip", true
+}
+
 func androidLoadTzinfoFromTzdata(file, name string) ([]byte, error) {
 	const (
 		headersize = 12 + 3*4

src/time/zoneinfo_android_test.go

@@ -10,8 +10,8 @@ import (
 )
 
 func TestAndroidTzdata(t *testing.T) {
-	ForceAndroidTzdataForTest(true)
-	defer ForceAndroidTzdataForTest(false)
+	undo := ForceAndroidTzdataForTest()
+	defer undo()
 	if _, err := LoadLocation("America/Los_Angeles"); err != nil {
 		t.Error(err)
 	}

src/time/zoneinfo_goroot.go

@@ -0,0 +1,14 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !ios && !android
+
+package time
+
+func gorootZoneSource(goroot string) (string, bool) {
+	if goroot == "" {
+		return "", false
+	}
+	return goroot + "/lib/time/zoneinfo.zip", true
+}

src/time/zoneinfo_ios.go

@@ -7,20 +7,20 @@
 package time
 
 import (
-	"runtime"
 	"syscall"
 )
 
-var zoneSources = []string{
-	getZoneRoot() + "/zoneinfo.zip",
-}
+var platformZoneSources []string // none on iOS
 
-func getZoneRoot() string {
+func gorootZoneSource(goroot string) (string, bool) {
 	// The working directory at initialization is the root of the
 	// app bundle: "/private/.../bundlename.app". That's where we
 	// keep zoneinfo.zip for tethered iOS builds.
 	// For self-hosted iOS builds, the zoneinfo.zip is in GOROOT.
-	roots := []string{runtime.GOROOT() + "/lib/time"}
+	var roots []string
+	if goroot != "" {
+		roots = append(roots, goroot+"/lib/time")
+	}
 	wd, err := syscall.Getwd()
 	if err == nil {
 		roots = append(roots, wd)
@@ -33,10 +33,10 @@ func getZoneRoot() string {
 		}
 		defer syscall.Close(fd)
 		if err := syscall.Fstat(fd, &st); err == nil {
-			return r
+			return r + "/zoneinfo.zip", true
 		}
 	}
-	return "/XXXNOEXIST"
+	return "", false
 }
 
 func initLocal() {

src/time/zoneinfo_js.go

@@ -7,15 +7,13 @@
 package time
 
 import (
-	"runtime"
 	"syscall/js"
 )
 
-var zoneSources = []string{
+var platformZoneSources = []string{
 	"/usr/share/zoneinfo/",
 	"/usr/share/lib/zoneinfo/",
 	"/usr/lib/locale/TZ/",
-	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
 }
 
 func initLocal() {

src/time/zoneinfo_plan9.go

@@ -7,13 +7,10 @@
 package time
 
 import (
-	"runtime"
 	"syscall"
 )
 
-var zoneSources = []string{
-	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
-}
+var platformZoneSources []string // none on Plan 9
 
 func isSpace(r rune) bool {
 	return r == ' ' || r == '\t' || r == '\n'

src/time/zoneinfo_read.go

@@ -528,7 +528,7 @@ func loadTzinfo(name string, source string) ([]byte, error) {
 // and parsed is returned as a Location.
 func loadLocation(name string, sources []string) (z *Location, firstErr error) {
 	for _, source := range sources {
-		var zoneData, err = loadTzinfo(name, source)
+		zoneData, err := loadTzinfo(name, source)
 		if err == nil {
 			if z, err = LoadLocationFromTZData(name, zoneData); err == nil {
 				return z, nil
@@ -539,9 +539,20 @@ func loadLocation(name string, sources []string) (z *Location, firstErr error) {
 		}
 	}
 	if loadFromEmbeddedTZData != nil {
-		zonedata, err := loadFromEmbeddedTZData(name)
+		zoneData, err := loadFromEmbeddedTZData(name)
 		if err == nil {
-			if z, err = LoadLocationFromTZData(name, []byte(zonedata)); err == nil {
+			if z, err = LoadLocationFromTZData(name, []byte(zoneData)); err == nil {
+				return z, nil
+			}
+		}
+		if firstErr == nil && err != syscall.ENOENT {
+			firstErr = err
+		}
+	}
+	if source, ok := gorootZoneSource(runtime.GOROOT()); ok {
+		zoneData, err := loadTzinfo(name, source)
+		if err == nil {
+			if z, err = LoadLocationFromTZData(name, zoneData); err == nil {
 				return z, nil
 			}
 		}

src/time/zoneinfo_test.go

@@ -66,8 +66,8 @@ func TestLoadLocationValidatesNames(t *testing.T) {
 }
 
 func TestVersion3(t *testing.T) {
-	time.ForceZipFileForTesting(true)
-	defer time.ForceZipFileForTesting(false)
+	undo := time.DisablePlatformSources()
+	defer undo()
 	_, err := time.LoadLocation("Asia/Jerusalem")
 	if err != nil {
 		t.Fatal(err)
@@ -78,8 +78,8 @@ func TestVersion3(t *testing.T) {
 // transition time. To do this we explicitly check early dates in a
 // couple of specific timezones.
 func TestFirstZone(t *testing.T) {
-	time.ForceZipFileForTesting(true)
-	defer time.ForceZipFileForTesting(false)
+	undo := time.DisablePlatformSources()
+	defer undo()
 
 	const format = "Mon, 02 Jan 2006 15:04:05 -0700 (MST)"
 	var tests = []struct {
@@ -128,16 +128,20 @@ func TestLocationNames(t *testing.T) {
 }
 
 func TestLoadLocationFromTZData(t *testing.T) {
-	time.ForceZipFileForTesting(true)
-	defer time.ForceZipFileForTesting(false)
+	undo := time.DisablePlatformSources()
+	defer undo()
 
 	const locationName = "Asia/Jerusalem"
 	reference, err := time.LoadLocation(locationName)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	tzinfo, err := time.LoadTzinfo(locationName, time.OrigZoneSources[len(time.OrigZoneSources)-1])
+	gorootSource, ok := time.GorootZoneSource("../..")
+	if !ok {
+		t.Fatal("Failed to locate tzinfo source in GOROOT.")
+	}
+	tzinfo, err := time.LoadTzinfo(locationName, gorootSource)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -153,8 +157,8 @@ func TestLoadLocationFromTZData(t *testing.T) {
 
 // Issue 30099.
 func TestEarlyLocation(t *testing.T) {
-	time.ForceZipFileForTesting(true)
-	defer time.ForceZipFileForTesting(false)
+	undo := time.DisablePlatformSources()
+	defer undo()
 
 	const locName = "America/New_York"
 	loc, err := time.LoadLocation(locName)

src/time/zoneinfo_unix.go

@@ -12,17 +12,15 @@
 package time
 
 import (
-	"runtime"
 	"syscall"
 )
 
 // Many systems use /usr/share/zoneinfo, Solaris 2 has
 // /usr/share/lib/zoneinfo, IRIX 6 has /usr/lib/locale/TZ.
-var zoneSources = []string{
+var platformZoneSources = []string{
 	"/usr/share/zoneinfo/",
 	"/usr/share/lib/zoneinfo/",
 	"/usr/lib/locale/TZ/",
-	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
 }
 
 func initLocal() {
@@ -57,7 +55,7 @@ func initLocal() {
 				return
 			}
 		} else if tz != "" && tz != "UTC" {
-			if z, err := loadLocation(tz, zoneSources); err == nil {
+			if z, err := loadLocation(tz, platformZoneSources); err == nil {
 				localLoc = *z
 				return
 			}

src/time/zoneinfo_windows.go

@@ -7,13 +7,10 @@ package time
 import (
 	"errors"
 	"internal/syscall/windows/registry"
-	"runtime"
 	"syscall"
 )
 
-var zoneSources = []string{
-	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
-}
+var platformZoneSources []string // none: Windows uses system calls instead
 
 // TODO(rsc): Fall back to copy of zoneinfo files.