x/tools/cmd/gotype: support type checking of xtest packages.

As noted by griesemer in golang/go#18799, this doesn't address the issues
raised in golang/go#11415 because when checking an xtest package the
corresponding package is assumed to have been installed. This
however is similar to the assumptions made by go vet (raised
as an issue in golang/go#16086). So whilst not perfect, it will probably
suffice until golang/go#11415 is resolved.

Fixes golang/go#18799

Change-Id: I1ea005c402e5d6f5abddda68fee6386b0531dfba
Reviewed-on: https://go-review.googlesource.com/36992
Reviewed-by: Robert Griesemer <[email protected]>

cmd/gotype/gotype.go

@@ -67,6 +67,16 @@ func initSizes() {
 
 func usage() {
 	fmt.Fprintln(os.Stderr, "usage: gotype [flags] [path ...]")
+	fmt.Fprintln(os.Stderr, "")
+	fmt.Fprintln(os.Stderr, "If no path is provided, gotype processes stdin.")
+	fmt.Fprintln(os.Stderr, "")
+	fmt.Fprintln(os.Stderr, "If a single directory is provided, gotype processes files in that directory.")
+	fmt.Fprintln(os.Stderr, "If the -a flag is provided gotype also processes the _test.go files in the directory.")
+	fmt.Fprintln(os.Stderr, "If the directory contains an xtest package, gotype -a will separately process the xtest")
+	fmt.Fprintln(os.Stderr, "package (it assumes the package itself is installed).")
+	fmt.Fprintln(os.Stderr, "")
+	fmt.Fprintln(os.Stderr, "Otherwise, the paths are processed as files belonging to the same package.")
+	fmt.Fprintln(os.Stderr, "")
 	flag.PrintDefaults()
 	os.Exit(2)
 }
@@ -137,49 +147,65 @@ func parseFiles(filenames []string) ([]*ast.File, error) {
 	return files, nil
 }
 
-func parseDir(dirname string) ([]*ast.File, error) {
+func parseDir(dirname string) (files, xfiles []*ast.File, err error) {
 	ctxt := build.Default
 	pkginfo, err := ctxt.ImportDir(dirname, 0)
 	if _, nogo := err.(*build.NoGoError); err != nil && !nogo {
-		return nil, err
+		return
 	}
+
 	filenames := append(pkginfo.GoFiles, pkginfo.CgoFiles...)
 	if *allFiles {
 		filenames = append(filenames, pkginfo.TestGoFiles...)
 	}
 
+	var xfilenames []string
+	if *allFiles {
+		xfilenames = pkginfo.XTestGoFiles
+	}
+
 	// complete file names
 	for i, filename := range filenames {
 		filenames[i] = filepath.Join(dirname, filename)
 	}
+	for i, filename := range xfilenames {
+		xfilenames[i] = filepath.Join(dirname, filename)
+	}
 
-	return parseFiles(filenames)
+	if files, err = parseFiles(filenames); err != nil {
+		return
+	}
+
+	xfiles, err = parseFiles(xfilenames)
+	return
 }
 
-func getPkgFiles(args []string) ([]*ast.File, error) {
+func getPkgFiles(args []string) (files, xfiles []*ast.File, err error) {
 	if len(args) == 0 {
 		// stdin
 		file, err := parseStdin()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return []*ast.File{file}, nil
+		return []*ast.File{file}, nil, nil
 	}
 
 	if len(args) == 1 {
 		// possibly a directory
 		path := args[0]
-		info, err := os.Stat(path)
+		var info os.FileInfo
+		info, err = os.Stat(path)
 		if err != nil {
-			return nil, err
+			return
 		}
 		if info.IsDir() {
 			return parseDir(path)
 		}
 	}
 
 	// list of files
-	return parseFiles(args)
+	files, err = parseFiles(args)
+	return
 }
 
 func checkPkgFiles(files []*ast.File) {
@@ -240,15 +266,24 @@ func main() {
 
 	start := time.Now()
 
-	files, err := getPkgFiles(flag.Args())
+	files, xfiles, err := getPkgFiles(flag.Args())
 	if err != nil {
 		report(err)
 		os.Exit(2)
 	}
 
-	checkPkgFiles(files)
-	if errorCount > 0 {
-		os.Exit(2)
+	if len(files) > 0 {
+		checkPkgFiles(files)
+		if errorCount > 0 {
+			os.Exit(2)
+		}
+	}
+
+	if len(xfiles) > 0 {
+		checkPkgFiles(xfiles)
+		if errorCount > 0 {
+			os.Exit(2)
+		}
 	}
 
 	if *verbose {