go/format: fix //line corner case when formatting statements

The code formatting mechanism can be applied to partial Go code,
such as a list of statements. The statements are wrapped into a
function definition (to be parsed fine), and unwrapped after formatting.

When the statements contain //line annotations, it may fail,
because not all comments are flushed by the printer before the final '}'.
Formatting "\ta()\n//line :1" results in "\ta() }\n\n//line", which
is wrong.

Tweaked the wrapping/unwrapping code to make sure comments are flushed
before the '}'.

Fixes #11276

Change-Id: Id15c80279b0382ee9ed939cca1647f525c4929f5
Reviewed-on: https://go-review.googlesource.com/11282
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/go/format/format_test.go b/src/go/format/format_test.go
index d7846bec6523269a9b6ec8022dc3271d14bf3b0c..000c611aa25525e318377639cec6b8212a9c9d69 100644 (file)
--- a/src/go/format/format_test.go
+++ b/src/go/format/format_test.go
@@ -91,7 +91,11 @@ var tests = []string{
        "\n\t\t\n\n\t\t\tx := 0\n\t\t\tconst s = `\n\t\tfoo\n`\n\n\n", // no indentation removed inside raw strings
 
        // comments
-       "i := 5 /* Comment */", // Issue 5551.
+       "i := 5 /* Comment */",         // Issue 5551.
+       "\ta()\n//line :1",             // Issue 11276.
+       "\t//xxx\n\ta()\n//line :2",    // Issue 11276.
+       "\ta() //line :1\n\tb()\n",     // Issue 11276.
+       "x := 0\n//line :1\n//line :2", // Issue 11276.
 
        // erroneous programs
        "ERROR1 + 2 +",

diff --git a/src/internal/format/format.go b/src/internal/format/format.go
index f8812ffe97a8371481c71f8fe5a8af31e03562e9..a8270ba669a97dfad6f26bc2ed0bd2b908e3b04e 100644 (file)
--- a/src/internal/format/format.go
+++ b/src/internal/format/format.go
@@ -58,8 +58,9 @@ func Parse(fset *token.FileSet, filename string, src []byte, fragmentOk bool) (
        // by inserting a package clause and turning the list
        // into a function body.  This handles expressions too.
        // Insert using a ;, not a newline, so that the line numbers
-       // in fsrc match the ones in src.
-       fsrc := append(append([]byte("package p; func _() {"), src...), '\n', '}')
+       // in fsrc match the ones in src. Add an extra '\n' before the '}'
+       // to make sure comments are flushed before the '}'.
+       fsrc := append(append([]byte("package p; func _() {"), src...), '\n', '\n', '}')
        file, err = parser.ParseFile(fset, filename, fsrc, parserMode)
        if err == nil {
                sourceAdj = func(src []byte, indent int) []byte {
@@ -71,7 +72,8 @@ func Parse(fset *token.FileSet, filename string, src []byte, fragmentOk bool) (
                        // Gofmt has turned the ; into a \n\n.
                        // There will be two non-blank lines with indent, hence 2*indent.
                        src = src[2*indent+len("package p\n\nfunc _() {"):]
-                       src = src[:len(src)-(indent+len("\n}\n"))]
+                       // Remove only the "}\n" suffix: remaining whitespaces will be trimmed anyway
+                       src = src[:len(src)-len("}\n")]
                        return bytes.TrimSpace(src)
                }
                // Gofmt has also indented the function body one level.