path/filepath: use fsutil with TestEvalSymlinksCanonicalNames

TestEvalSymlinksCanonicalNames fails on system where 8dot3 name creation
is disabled. Add new test that temporarily changes 8dot3 name creation
file system setting and runs TestEvalSymlinksCanonicalNames under that
setting. New test requires administrator access and modifies important
file system setting, so don't run the test unless explicitly requested
by specifying new test flag.

Updates #13980

Change-Id: I598b5b956e6bd0ed556e79d350cb244808c89c0b
Reviewed-on: https://go-review.googlesource.com/20863
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

src/path/filepath/path_windows_test.go

@@ -5,6 +5,8 @@
 package filepath_test
 
 import (
+	"flag"
+	"fmt"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -174,3 +176,106 @@ func TestEvalSymlinksCanonicalNames(t *testing.T) {
 		}
 	}
 }
+
+// checkVolume8dot3Setting runs "fsutil 8dot3name query c:" command
+// (where c: is vol parameter) to discover "8dot3 name creation state".
+// The state is combination of 2 flags. The global flag controls if it
+// is per volume or global setting:
+//   0 - Enable 8dot3 name creation on all volumes on the system
+//   1 - Disable 8dot3 name creation on all volumes on the system
+//   2 - Set 8dot3 name creation on a per volume basis
+//   3 - Disable 8dot3 name creation on all volumes except the system volume
+// If global flag is set to 2, then per-volume flag needs to be examined:
+//   0 - Enable 8dot3 name creation on this volume
+//   1 - Disable 8dot3 name creation on this volume
+// checkVolume8dot3Setting verifies that "8dot3 name creation" flags
+// are set to 2 and 0, if enabled parameter is true, or 2 and 1, if enabled
+// is false. Otherwise checkVolume8dot3Setting returns error.
+func checkVolume8dot3Setting(vol string, enabled bool) error {
+	// It appears, on some systems "fsutil 8dot3name query ..." command always
+	// exits with error. Ignore exit code, and look at fsutil output instead.
+	out, _ := exec.Command("fsutil", "8dot3name", "query", vol).CombinedOutput()
+	// Check that system has "Volume level setting" set.
+	expected := "The registry state of NtfsDisable8dot3NameCreation is 2, the default (Volume level setting)"
+	if !strings.Contains(string(out), expected) {
+		// Windows 10 version of fsutil has different output message.
+		expectedWindow10 := "The registry state is: 2 (Per volume setting - the default)"
+		if !strings.Contains(string(out), expectedWindow10) {
+			return fmt.Errorf("fsutil output should contain %q, but is %q", expected, string(out))
+		}
+	}
+	// Now check the volume setting.
+	expected = "Based on the above two settings, 8dot3 name creation is %s on %s"
+	if enabled {
+		expected = fmt.Sprintf(expected, "enabled", vol)
+	} else {
+		expected = fmt.Sprintf(expected, "disabled", vol)
+	}
+	if !strings.Contains(string(out), expected) {
+		return fmt.Errorf("unexpected fsutil output: %q", string(out))
+	}
+	return nil
+}
+
+func setVolume8dot3Setting(vol string, enabled bool) error {
+	cmd := []string{"fsutil", "8dot3name", "set", vol}
+	if enabled {
+		cmd = append(cmd, "0")
+	} else {
+		cmd = append(cmd, "1")
+	}
+	// It appears, on some systems "fsutil 8dot3name set ..." command always
+	// exits with error. Ignore exit code, and look at fsutil output instead.
+	out, _ := exec.Command(cmd[0], cmd[1:]...).CombinedOutput()
+	if string(out) != "\r\nSuccessfully set 8dot3name behavior.\r\n" {
+		// Windows 10 version of fsutil has different output message.
+		expectedWindow10 := "Successfully %s 8dot3name generation on %s\r\n"
+		if enabled {
+			expectedWindow10 = fmt.Sprintf(expectedWindow10, "enabled", vol)
+		} else {
+			expectedWindow10 = fmt.Sprintf(expectedWindow10, "disabled", vol)
+		}
+		if string(out) != expectedWindow10 {
+			return fmt.Errorf("%v command failed: %q", cmd, string(out))
+		}
+	}
+	return nil
+}
+
+var runFSModifyTests = flag.Bool("run_fs_modify_tests", false, "run tests which modify filesystem parameters")
+
+// This test assumes registry state of NtfsDisable8dot3NameCreation is 2,
+// the default (Volume level setting).
+func TestEvalSymlinksCanonicalNamesWith8dot3Disabled(t *testing.T) {
+	if !*runFSModifyTests {
+		t.Skip("skipping test that modifies file system setting; enable with -run_fs_modify_tests")
+	}
+	tempVol := filepath.VolumeName(os.TempDir())
+	if len(tempVol) != 2 {
+		t.Fatalf("unexpected temp volume name %q", tempVol)
+	}
+
+	err := checkVolume8dot3Setting(tempVol, true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = setVolume8dot3Setting(tempVol, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := setVolume8dot3Setting(tempVol, true)
+		if err != nil {
+			t.Fatal(err)
+		}
+		err = checkVolume8dot3Setting(tempVol, true)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+	err = checkVolume8dot3Setting(tempVol, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	TestEvalSymlinksCanonicalNames(t)
+}