time: support colon at start of TZ value

According to POSIX, there are three formats for TZ variable. When
it refers to timezone file, it should starts with a colon. This commit
removes the colon if it exists, so that it keeps compatible with both
the spec and the old behavior.

Change-Id: I30cfeaea530d24e174de309952338cb1146694a5
GitHub-Last-Rev: 11d83d11ca2eca9d542036cf5e23559388fd323e
GitHub-Pull-Request: golang/go#27570
Reviewed-on: https://go-review.googlesource.com/c/go/+/134217
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Dmitri Shuralyov <dmitshur@golang.org>

diff --git a/src/time/zoneinfo_unix.go b/src/time/zoneinfo_unix.go
index c311ddc33f360324936d9369f19bd0ffada3b3f4..80724eb30a72b2da80e09e832a37b806b86a062a 100644 (file)
--- a/src/time/zoneinfo_unix.go
+++ b/src/time/zoneinfo_unix.go
@@ -29,7 +29,9 @@ func initLocal() {
        // consult $TZ to find the time zone to use.
        // no $TZ means use the system default /etc/localtime.
        // $TZ="" means use UTC.
-       // $TZ="foo" means use /usr/share/zoneinfo/foo.
+       // $TZ="foo" or $TZ=":foo" if foo is an absolute path, then the file pointed
+       // by foo will be used to initialize timezone; otherwise, file
+       // /usr/share/zoneinfo/foo will be used.
 
        tz, ok := syscall.Getenv("TZ")
        switch {
@@ -40,10 +42,25 @@ func initLocal() {
                        localLoc.name = "Local"
                        return
                }
-       case tz != "" && tz != "UTC":
-               if z, err := loadLocation(tz, zoneSources); err == nil {
-                       localLoc = *z
-                       return
+       case tz != "":
+               if tz[0] == ':' {
+                       tz = tz[1:]
+               }
+               if tz != "" && tz[0] == '/' {
+                       if z, err := loadLocation(tz, []string{""}); err == nil {
+                               localLoc = *z
+                               if tz == "/etc/localtime" {
+                                       localLoc.name = "Local"
+                               } else {
+                                       localLoc.name = tz
+                               }
+                               return
+                       }
+               } else if tz != "" && tz != "UTC" {
+                       if z, err := loadLocation(tz, zoneSources); err == nil {
+                               localLoc = *z
+                               return
+                       }
                }
        }
 

diff --git a/src/time/zoneinfo_unix_test.go b/src/time/zoneinfo_unix_test.go
new file mode 100644 (file)
index 0000000..2d45b83
--- /dev/null
+++ b/src/time/zoneinfo_unix_test.go
@@ -0,0 +1,90 @@
+// Copyright 2020 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.
+
+// +build aix darwin,amd64 dragonfly freebsd linux,!android netbsd openbsd solaris
+
+package time_test
+
+import (
+       "os"
+       "testing"
+       "time"
+)
+
+func TestEnvTZUsage(t *testing.T) {
+       const env = "TZ"
+       tz, ok := os.LookupEnv(env)
+       if !ok {
+               defer os.Unsetenv(env)
+       } else {
+               defer os.Setenv(env, tz)
+       }
+       defer time.ForceUSPacificForTesting()
+
+       localZoneName := "Local"
+       // The file may not exist.
+       if _, err := os.Stat("/etc/localtime"); os.IsNotExist(err) {
+               localZoneName = "UTC"
+       }
+
+       cases := []struct {
+               nilFlag bool
+               tz      string
+               local   string
+       }{
+               // no $TZ means use the system default /etc/localtime.
+               {true, "", localZoneName},
+               // $TZ="" means use UTC.
+               {false, "", "UTC"},
+               {false, ":", "UTC"},
+               {false, "Asia/Shanghai", "Asia/Shanghai"},
+               {false, ":Asia/Shanghai", "Asia/Shanghai"},
+               {false, "/etc/localtime", localZoneName},
+               {false, ":/etc/localtime", localZoneName},
+       }
+
+       for _, c := range cases {
+               time.ResetLocalOnceForTest()
+               if c.nilFlag {
+                       os.Unsetenv(env)
+               } else {
+                       os.Setenv(env, c.tz)
+               }
+               if time.Local.String() != c.local {
+                       t.Errorf("invalid Local location name for %q: got %q want %q", c.tz, time.Local, c.local)
+               }
+       }
+
+       time.ResetLocalOnceForTest()
+       // The file may not exist on Solaris 2 and IRIX 6.
+       path := "/usr/share/zoneinfo/Asia/Shanghai"
+       os.Setenv(env, path)
+       if _, err := os.Stat(path); os.IsNotExist(err) {
+               if time.Local.String() != "UTC" {
+                       t.Errorf(`invalid path should fallback to UTC: got %q want "UTC"`, time.Local)
+               }
+               return
+       }
+       if time.Local.String() != path {
+               t.Errorf(`custom path should lead to path itself: got %q want %q`, time.Local, path)
+       }
+
+       timeInUTC := time.Date(2009, 1, 1, 12, 0, 0, 0, time.UTC)
+       sameTimeInShanghai := time.Date(2009, 1, 1, 20, 0, 0, 0, time.Local)
+       if !timeInUTC.Equal(sameTimeInShanghai) {
+               t.Errorf("invalid timezone: got %q want %q", timeInUTC, sameTimeInShanghai)
+       }
+
+       time.ResetLocalOnceForTest()
+       os.Setenv(env, ":"+path)
+       if time.Local.String() != path {
+               t.Errorf(`custom path should lead to path itself: got %q want %q`, time.Local, path)
+       }
+
+       time.ResetLocalOnceForTest()
+       os.Setenv(env, path[:len(path)-1])
+       if time.Local.String() != "UTC" {
+               t.Errorf(`invalid path should fallback to UTC: got %q want "UTC"`, time.Local)
+       }
+}