From 7f1538dc8cdc02abc028ada3320eb663d18c00af Mon Sep 17 00:00:00 2001
From: Alan Donovan <adonovan@google.com>
Date: Tue, 21 Oct 2014 11:15:00 -0400
Subject: [PATCH] refactor: don't litter the source tree with backup turdlets.

Also, restore from backup if the replacement file cannot be written.

LGTM=sameer
R=sameer
CC=golang-codereviews
https://golang.org/cl/155660043
---
 refactor/rename/rename.go | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/refactor/rename/rename.go b/refactor/rename/rename.go
index 53d88801..12fc149f 100644
--- a/refactor/rename/rename.go
+++ b/refactor/rename/rename.go
@@ -304,8 +304,21 @@ func plural(n int) string {
 	return ""
 }
 
+func writeFile(name string, fset *token.FileSet, f *ast.File) error {
+	out, err := os.Create(name)
+	if err != nil {
+		// assume error includes the filename
+		return fmt.Errorf("failed to open file: %s", err)
+	}
+	if err := format.Node(out, fset, f); err != nil {
+		out.Close() // ignore error
+		return fmt.Errorf("failed to write file: %s", err)
+	}
+	return out.Close()
+}
+
 var rewriteFile = func(fset *token.FileSet, f *ast.File, orig string) (err error) {
-	backup := orig + ".prename"
+	backup := orig + ".gorename.backup"
 	// TODO(adonovan): print packages and filenames in a form useful
 	// to editors (so they can reload files).
 	if Verbose {
@@ -315,18 +328,12 @@ var rewriteFile = func(fset *token.FileSet, f *ast.File, orig string) (err error
 		return fmt.Errorf("failed to make backup %s -> %s: %s",
 			orig, filepath.Base(backup), err)
 	}
-	out, err := os.Create(orig)
-	if err != nil {
-		// assume error includes the filename
-		return fmt.Errorf("failed to open file: %s", err)
-	}
-	defer func() {
-		if closeErr := out.Close(); err == nil {
-			err = closeErr // don't clobber existing error
-		}
-	}()
-	if err := format.Node(out, fset, f); err != nil {
-		return fmt.Errorf("failed to write file: %s", err)
+	if err := writeFile(orig, fset, f); err != nil {
+		// Restore the file from the backup.
+		os.Remove(orig)         // ignore error
+		os.Rename(backup, orig) // ignore error
+		return err
 	}
+	os.Remove(backup) // ignore error
 	return nil
 }