confd does not leave behind temporary files

confd leaves behind temporary files if there are errors during the
processing of templates.

Fix this issue by removing temporary files if errors occure during
template processing.

Fixes kelseyhightower#288

resource/template/resource.go

@@ -106,24 +106,30 @@ func (t *TemplateResource) setVars() error {
 // It returns an error if any.
 func (t *TemplateResource) createStageFile() error {
 	log.Debug("Using source template " + t.Src)
+
 	if !isFileExist(t.Src) {
 		return errors.New("Missing template: " + t.Src)
 	}
-	// create TempFile in Dest directory to avoid cross-filesystem issues
-	temp, err := ioutil.TempFile(filepath.Dir(t.Dest), "."+filepath.Base(t.Dest))
-	if err != nil {
-		return err
-	}
-	defer temp.Close()
+
 	log.Debug("Compiling source template " + t.Src)
 	tmpl, err := template.New(path.Base(t.Src)).Funcs(t.funcMap).ParseFiles(t.Src)
 	if err != nil {
 		return fmt.Errorf("Unable to process template %s, %s", t.Src, err)
 	}
 
+	// create TempFile in Dest directory to avoid cross-filesystem issues
+	temp, err := ioutil.TempFile(filepath.Dir(t.Dest), "."+filepath.Base(t.Dest))
+	if err != nil {
+		return err
+	}
+
 	if err = tmpl.Execute(temp, nil); err != nil {
+		temp.Close()
+		os.Remove(temp.Name())
 		return err
 	}
+	defer temp.Close()
+
 	// Set the owner, group, and mode on the stage file now to make it easier to
 	// compare against the destination configuration file later.
 	os.Chmod(temp.Name(), t.FileMode)
@@ -144,6 +150,7 @@ func (t *TemplateResource) sync() error {
 	} else {
 		defer os.Remove(staged)
 	}
+
 	log.Debug("Comparing candidate config to " + t.Dest)
 	ok, err := sameConfig(staged, t.Dest)
 	if err != nil {