os/user: don't skip TestLookupGroup if supported

CL 37664 implemented this functionality, yet the tests were skipped.

Introduce and use additional variable groupListImplemented to
distinguish between these cases and enable TestLookupGroup for
supported configurations (which looks like all but plan9).

Change-Id: Iabaa7f08b4551dc67e67bdb6e715f15bb20d6218
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/330751
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

5 files changed, 20 insertions, 7 deletions

diff --git a/src/os/user/lookup_plan9.go b/src/os/user/lookup_plan9.go
index 51caf55935..07939363e7 100644
--- a/src/os/user/lookup_plan9.go
+++ b/src/os/user/lookup_plan9.go
@@ -20,6 +20,7 @@ const (
 func init() {
 	userImplemented = false
 	groupImplemented = false
+	groupListImplemented = false
 }
 
 func current() (*User, error) {
diff --git a/src/os/user/lookup_stubs.go b/src/os/user/lookup_stubs.go
index c975a11964..d8e3d4866a 100644
--- a/src/os/user/lookup_stubs.go
+++ b/src/os/user/lookup_stubs.go
@@ -16,7 +16,7 @@ import (
 )
 
 func init() {
-	groupImplemented = false
+	groupListImplemented = false
 }
 
 func current() (*User, error) {
diff --git a/src/os/user/lookup_unix.go b/src/os/user/lookup_unix.go
index 97c611fad4..dffea4a885 100644
--- a/src/os/user/lookup_unix.go
+++ b/src/os/user/lookup_unix.go
@@ -18,13 +18,15 @@ import (
 	"strings"
 )
 
-const groupFile = "/etc/group"
-const userFile = "/etc/passwd"
+const (
+	groupFile = "/etc/group"
+	userFile  = "/etc/passwd"
+)
 
 var colon = []byte{':'}
 
 func init() {
-	groupImplemented = false
+	groupListImplemented = false
 }
 
 // lineFunc returns a value, an error, or (nil, nil) to skip the row.
diff --git a/src/os/user/user.go b/src/os/user/user.go
index c1b8101c86..4e1b5b3407 100644
--- a/src/os/user/user.go
+++ b/src/os/user/user.go
@@ -20,9 +20,12 @@ import (
 	"strconv"
 )
 
+// These may be set to false in init() for a particular platform and/or
+// build flags to let the tests know to skip tests of some features.
 var (
-	userImplemented  = true // set to false by lookup_stubs.go's init
-	groupImplemented = true // set to false by lookup_stubs.go's init
+	userImplemented      = true
+	groupImplemented     = true
+	groupListImplemented = true
 )
 
 // User represents a user account.
diff --git a/src/os/user/user_test.go b/src/os/user/user_test.go
index 1112c78c00..d8a465edac 100644
--- a/src/os/user/user_test.go
+++ b/src/os/user/user_test.go
@@ -119,8 +119,15 @@ func TestLookupGroup(t *testing.T) {
 	}
 }
 
+func checkGroupList(t *testing.T) {
+	t.Helper()
+	if !groupListImplemented {
+		t.Skip("user: group list not implemented; skipping test")
+	}
+}
+
 func TestGroupIds(t *testing.T) {
-	checkGroup(t)
+	checkGroupList(t)
 	if runtime.GOOS == "aix" {
 		t.Skip("skipping GroupIds, see golang.org/issue/30563")
 	}