go/scanner: interpret //line directives sans filename sensibly

A //line directive without a filename now denotes the same
filename as the previous line (as in C).
Previously it denoted the file's directory (!).

Fixes #7765

LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/86990044

diff --git a/src/pkg/go/scanner/scanner.go b/src/pkg/go/scanner/scanner.go
index 25588ba3b0c0bb166dd518a2adbdb2c5df729501..c83e4fa8160ac8c5f43aaf5968f296ff4e225566 100644 (file)
--- a/src/pkg/go/scanner/scanner.go
+++ b/src/pkg/go/scanner/scanner.go
@@ -148,11 +148,17 @@ func (s *Scanner) interpretLineComment(text []byte) {
                // get filename and line number, if any
                if i := bytes.LastIndex(text, []byte{':'}); i > 0 {
                        if line, err := strconv.Atoi(string(text[i+1:])); err == nil && line > 0 {
-                               // valid //line filename:line comment;
-                               filename := filepath.Clean(string(text[len(prefix):i]))
-                               if !filepath.IsAbs(filename) {
-                                       // make filename relative to current directory
-                                       filename = filepath.Join(s.dir, filename)
+                               // valid //line filename:line comment
+                               filename := string(bytes.TrimSpace(text[len(prefix):i]))
+                               if filename == "" {
+                                       // assume same file as for previous line
+                                       filename = s.file.Position(s.file.Pos(s.lineOffset)).Filename
+                               } else {
+                                       filename = filepath.Clean(filename)
+                                       if !filepath.IsAbs(filename) {
+                                               // make filename relative to current directory
+                                               filename = filepath.Join(s.dir, filename)
+                                       }
                                }
                                // update scanner position
                                s.file.AddLineInfo(s.lineOffset+len(text)+1, filename, line) // +len(text)+1 since comment applies to next line

diff --git a/src/pkg/go/scanner/scanner_test.go b/src/pkg/go/scanner/scanner_test.go
index e0d0b54f68e6d73d11cf7b05bbc290982613d5b3..55e55abaecf90f5ec9912ffc5b66c8bb2593090f 100644 (file)
--- a/src/pkg/go/scanner/scanner_test.go
+++ b/src/pkg/go/scanner/scanner_test.go
@@ -493,9 +493,10 @@ var segments = []segment{
        {"\nline3  //line File1.go:100", filepath.Join("dir", "TestLineComments"), 3}, // bad line comment, ignored
        {"\nline4", filepath.Join("dir", "TestLineComments"), 4},
        {"\n//line File1.go:100\n  line100", filepath.Join("dir", "File1.go"), 100},
+       {"\n//line :42\n  line1", "dir/File1.go", 42},
        {"\n//line File2.go:200\n  line200", filepath.Join("dir", "File2.go"), 200},
-       {"\n//line :1\n  line1", "dir", 1},
-       {"\n//line foo:42\n  line42", filepath.Join("dir", "foo"), 42},
+       {"\n//line  \t :123\n  line1", "dir/File2.go", 123},
+       {"\n//line foo\t:42\n  line42", filepath.Join("dir", "foo"), 42},
        {"\n //line foo:42\n  line44", filepath.Join("dir", "foo"), 44},           // bad line comment, ignored
        {"\n//line foo 42\n  line46", filepath.Join("dir", "foo"), 46},            // bad line comment, ignored
        {"\n//line foo:42 extra text\n  line48", filepath.Join("dir", "foo"), 48}, // bad line comment, ignored