go.ast: add CommentGroup.Raw function

src/go/ast/ast.go

@@ -8,6 +8,7 @@ package ast
 
 import (
 	"go/token"
+	"runtime"
 	"strings"
 )
 
@@ -88,6 +89,27 @@ func stripTrailingWhitespace(s string) string {
 	return s[0:i]
 }
 
+// Raw returns the raw (original) text of the comment.
+// It includes the comment markers (//, /*, and */).
+// It adds a newline at the end of the comment.
+func (g *CommentGroup) Raw() string {
+	if g == nil {
+		return ""
+	}
+	var (
+		b  strings.Builder
+		ls = "\n"
+	)
+	if runtime.GOOS == "windows" {
+		ls = "\r\n"
+	}
+
+	for _, c := range g.List {
+		b.WriteString(c.Text + ls)
+	}
+	return b.String()
+}
+
 // Text returns the text of the comment.
 // Comment markers (//, /*, and */), the first space of a line comment, and
 // leading and trailing empty lines are removed.

src/go/ast/ast_test.go

@@ -8,7 +8,7 @@ import (
 	"testing"
 )
 
-var comments = []struct {
+var commentsText = []struct {
 	list []string
 	text string
 }{
@@ -39,7 +39,7 @@ var comments = []struct {
 }
 
 func TestCommentText(t *testing.T) {
-	for i, c := range comments {
+	for i, c := range commentsText {
 		list := make([]*Comment, len(c.list))
 		for i, s := range c.list {
 			list[i] = &Comment{Text: s}
@@ -52,6 +52,57 @@ func TestCommentText(t *testing.T) {
 	}
 }
 
+var commentsRaw = []struct {
+	list []string
+	raw  string
+}{
+	{[]string{"//"}, "//\n"},
+	{[]string{"//   "}, "//   \n"},
+	{[]string{"//", "//", "//   "}, "//\n//\n//   \n"},
+	{[]string{"// foo   "}, "// foo   \n"},
+	{[]string{"//", "//", "// foo"}, "//\n//\n// foo\n"},
+	{[]string{"// foo  bar  "}, "// foo  bar  \n"},
+	{[]string{"// foo", "// bar"}, "// foo\n// bar\n"},
+	{[]string{"// foo", "//", "//", "//", "// bar"},
+		"// foo\n//\n//\n//\n// bar\n"},
+	{[]string{"// foo", "/* bar */"}, "// foo\n/* bar */\n"},
+	{[]string{"//", "//", "//", "// foo", "//", "//", "//"},
+		"//\n//\n//\n// foo\n//\n//\n//\n"},
+
+	{[]string{"/**/"}, "/**/\n"},
+	{[]string{"/*   */"}, "/*   */\n"},
+	{[]string{"/**/", "/**/", "/*   */"},
+		"/**/\n/**/\n/*   */\n"},
+	{[]string{"/* Foo   */"}, "/* Foo   */\n"},
+	{[]string{"/* Foo  Bar  */"}, "/* Foo  Bar  */\n"},
+	{[]string{"/* Foo*/", "/* Bar*/"}, "/* Foo*/\n/* Bar*/\n"},
+	{[]string{"/* Foo*/", "/**/", "/**/", "/**/", "// Bar"},
+		"/* Foo*/\n/**/\n/**/\n/**/\n// Bar\n"},
+	{[]string{"/* Foo*/", "/*\n*/", "//", "/*\n*/", "// Bar"},
+		"/* Foo*/\n/*\n*/\n//\n/*\n*/\n// Bar\n"},
+	{[]string{"/* Foo*/", "// Bar"}, "/* Foo*/\n// Bar\n"},
+	{[]string{"/* Foo\n Bar*/"}, "/* Foo\n Bar*/\n"},
+
+	{[]string{"// foo", "//go:noinline", "// bar", "//:baz"},
+		"// foo\n//go:noinline\n// bar\n//:baz\n"},
+	{[]string{"// foo", "//lint123:ignore", "// bar"},
+		"// foo\n//lint123:ignore\n// bar\n"},
+}
+
+func TestCommentRaw(t *testing.T) {
+	for i, c := range commentsRaw {
+		list := make([]*Comment, len(c.list))
+		for i, s := range c.list {
+			list[i] = &Comment{Text: s}
+		}
+
+		text := (&CommentGroup{list}).Raw()
+		if text != c.raw {
+			t.Errorf("case %d: got %q; expected %q", i, text, c.raw)
+		}
+	}
+}
+
 var isDirectiveTests = []struct {
 	in string
 	ok bool