Error on invalid gopherjs test -c, -o flag usage.

dmitshur · dmitshur · commit df18d38287ab · 2018-02-27T14:20:48.000-05:00
This prevents a situation with confusing results by following the same behavior as cmd/go command. Fixes gopherjs#764.
diff --git a/tool.go b/tool.go
@@ -307,6 +307,13 @@ func main() {
 			patternContext := gbuild.NewBuildContext("", options.BuildTags)
 			args = (&gotool.Context{BuildContext: *patternContext}).ImportPaths(args)
 
+			if *compileOnly && len(args) > 1 {
+				return errors.New("cannot use -c flag with multiple packages")
+			}
+			if *outputFilename != "" && len(args) > 1 {
+				return errors.New("cannot use -o flag with multiple packages")
+			}
+
 			pkgs := make([]*gbuild.PackageData, len(args))
 			for i, pkgPath := range args {
 				var err error
