cmd/vet: accept space-separated tag lists for compatibility with cmd/go

Fixes #17148.

Change-Id: I4c66aa0733c249ee6019d1c4e802a7e30457d4b6
Reviewed-on: https://go-review.googlesource.com/32030
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/vet/main.go

@@ -25,7 +25,7 @@ import (
 
 var (
 	verbose = flag.Bool("v", false, "verbose")
-	tags    = flag.String("tags", "", "comma-separated list of build tags to apply when parsing")
+	tags    = flag.String("tags", "", "space-separated list of build tags to apply when parsing")
 	tagList = []string{} // exploded version of tags flag; set in main
 )
 
@@ -208,7 +208,10 @@ func main() {
 		}
 	}
 
-	tagList = strings.Split(*tags, ",")
+	// Accept space-separated tags because that matches
+	// the go command's other subcommands.
+	// Accept commas because go tool vet traditionally has.
+	tagList = strings.Fields(strings.Replace(*tags, ",", " ", -1))
 
 	initPrintFlags()
 	initUnusedFlags()

src/cmd/vet/vet_test.go

@@ -128,21 +128,24 @@ func run(c *exec.Cmd, t *testing.T) bool {
 // TestTags verifies that the -tags argument controls which files to check.
 func TestTags(t *testing.T) {
 	Build(t)
-	args := []string{
-		"-tags=testtag",
-		"-v", // We're going to look at the files it examines.
-		"testdata/tagtest",
-	}
-	cmd := exec.Command("./"+binary, args...)
-	output, err := cmd.CombinedOutput()
-	if err != nil {
-		t.Fatal(err)
-	}
-	// file1 has testtag and file2 has !testtag.
-	if !bytes.Contains(output, []byte(filepath.Join("tagtest", "file1.go"))) {
-		t.Error("file1 was excluded, should be included")
-	}
-	if bytes.Contains(output, []byte(filepath.Join("tagtest", "file2.go"))) {
-		t.Error("file2 was included, should be excluded")
+	for _, tag := range []string{"testtag", "x testtag y", "x,testtag,y"} {
+		t.Logf("-tags=%s", tag)
+		args := []string{
+			"-tags=" + tag,
+			"-v", // We're going to look at the files it examines.
+			"testdata/tagtest",
+		}
+		cmd := exec.Command("./"+binary, args...)
+		output, err := cmd.CombinedOutput()
+		if err != nil {
+			t.Fatal(err)
+		}
+		// file1 has testtag and file2 has !testtag.
+		if !bytes.Contains(output, []byte(filepath.Join("tagtest", "file1.go"))) {
+			t.Error("file1 was excluded, should be included")
+		}
+		if bytes.Contains(output, []byte(filepath.Join("tagtest", "file2.go"))) {
+			t.Error("file2 was included, should be excluded")
+		}
 	}
 }