time: correct path to time zone zip file on Unix

Most Unix systems have their own time zone data,
so we almost never get far enough in the list to
discover that we cannot fall back to the zip file.
Adjust testing to exercise the final fallback.

Plan 9 and Windows were already correct
(and are the main users of the zip file).

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/19280043

src/pkg/time/export_test.go

@@ -18,4 +18,7 @@ func ForceUSPacificForTesting() {
 	localOnce.Do(initTestingZone)
 }
 
-var ParseTimeZone = parseTimeZone
+var (
+	ForceZipFileForTesting = forceZipFileForTesting
+	ParseTimeZone          = parseTimeZone
+)

src/pkg/time/time_test.go

@@ -578,6 +578,16 @@ func TestParseInSydney(t *testing.T) {
 	}
 }
 
+func TestLoadLocationZipFile(t *testing.T) {
+	ForceZipFileForTesting(true)
+	defer ForceZipFileForTesting(false)
+
+	_, err := LoadLocation("Australia/Sydney")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 var rubyTests = []ParseTest{
 	{"RubyDate", RubyDate, "Thu Feb 04 21:00:57 -0800 2010", true, true, 1, 0},
 	// Ignore the time zone in the test. If it parses, it'll be OK.

src/pkg/time/zoneinfo_plan9.go

@@ -154,3 +154,7 @@ func loadLocation(name string) (*Location, error) {
 	}
 	return nil, errors.New("unknown time zone " + name)
 }
+
+func forceZipFileForTesting(zipOnly bool) {
+	// We only use the zip file anyway.
+}

src/pkg/time/zoneinfo_unix.go

@@ -32,7 +32,19 @@ var zoneDirs = []string{
 	"/usr/share/zoneinfo/",
 	"/usr/share/lib/zoneinfo/",
 	"/usr/lib/locale/TZ/",
-	runtime.GOROOT() + "/lib/time/zoneinfo/",
+	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
+}
+
+var origZoneDirs = zoneDirs
+
+func forceZipFileForTesting(zipOnly bool) {
+	zoneDirs = make([]string, len(origZoneDirs))
+	copy(zoneDirs, origZoneDirs)
+	if zipOnly {
+		for i := 0; i < len(zoneDirs)-1; i++ {
+			zoneDirs[i] = "/XXXNOEXIST"
+		}
+	}
 }
 
 func initLocal() {

src/pkg/time/zoneinfo_windows.go

@@ -264,3 +264,7 @@ func loadLocation(name string) (*Location, error) {
 	}
 	return nil, errors.New("unknown time zone " + name)
 }
+
+func forceZipFileForTesting(zipOnly bool) {
+	// We only use the zip file anyway.
+}