exp/ebnflint: test spec during 'go test'

This avoids the need for a custom Makefile.

R=gri
CC=golang-dev
https://golang.org/cl/5575045

src/pkg/exp/ebnflint/ebnflint.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"go/scanner"
 	"go/token"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -76,34 +77,46 @@ func main() {
 	flag.Parse()
 
 	var (
-		filename string
-		src      []byte
-		err      error
+		name string
+		r    io.Reader
 	)
 	switch flag.NArg() {
 	case 0:
-		filename = "<stdin>"
-		src, err = ioutil.ReadAll(os.Stdin)
+		name, r = "<stdin>", os.Stdin
 	case 1:
-		filename = flag.Arg(0)
-		src, err = ioutil.ReadFile(filename)
+		name = flag.Arg(0)
 	default:
 		usage()
 	}
-	if err != nil {
+
+	if err := verify(name, *start, r); err != nil {
 		report(err)
 	}
+}
 
-	if filepath.Ext(filename) == ".html" || bytes.Index(src, open) >= 0 {
-		src = extractEBNF(src)
+func verify(name, start string, r io.Reader) error {
+	if r == nil {
+		f, err := os.Open(name)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		r = f
 	}
 
-	grammar, err := ebnf.Parse(filename, bytes.NewBuffer(src))
+	src, err := ioutil.ReadAll(r)
 	if err != nil {
-		report(err)
+		return err
 	}
 
-	if err = ebnf.Verify(grammar, *start); err != nil {
-		report(err)
+	if filepath.Ext(name) == ".html" || bytes.Index(src, open) >= 0 {
+		src = extractEBNF(src)
+	}
+
+	grammar, err := ebnf.Parse(name, bytes.NewBuffer(src))
+	if err != nil {
+		return err
 	}
+
+	return ebnf.Verify(grammar, start)
 }

src/pkg/exp/ebnflint/ebnflint_test.go

+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"runtime"
+	"testing"
+)
+
+func TestSpec(t *testing.T) {
+	if err := verify(runtime.GOROOT()+"/doc/go_spec.html", "SourceFile", nil); err != nil {
+		t.Fatal(err)
+	}
+}