From db24f3cbd10603f852032a95b5983335b6b5aff2 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Fri, 17 Nov 2017 21:15:01 -0500
Subject: backend: Close the writer on finish

---
 backend.go | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/backend.go b/backend.go
index ff40f5b..fc67d82 100644
--- a/backend.go
+++ b/backend.go
@@ -10,23 +10,33 @@ import (
 // A Backend is something that consumes a fast-import stream; the
 // Backend object provides methods for writing to it.
 type Backend struct {
-	w   *bufio.Writer
+	w   io.WriteCloser
+	bw  *bufio.Writer
 	fiw *textproto.FIWriter
 	cbr *textproto.CatBlobReader
 
-	err error
+	err   error
 	onErr func(error) error
 }
 
-func NewBackend(fastImport io.Writer, catBlob io.Reader, onErr func(error) error) *Backend {
+func NewBackend(fastImport io.WriteCloser, catBlob io.Reader, onErr func(error) error) *Backend {
 	ret := &Backend{}
-	ret.w = bufio.NewWriter(fastImport)
-	ret.fiw = textproto.NewFIWriter(ret.w)
+	ret.w = fastImport
+	ret.bw = bufio.NewWriter(ret.w)
+	ret.fiw = textproto.NewFIWriter(ret.bw)
 	if catBlob != nil {
 		ret.cbr = textproto.NewCatBlobReader(catBlob)
 	}
 	ret.onErr = func(err error) error {
 		ret.err = err
+
+		// Close the underlying writer, but don't let the
+		// error mask the previous error.
+		err = ret.w.Close()
+		if ret.err == nil {
+			ret.err = err
+		}
+
 		if onErr != nil {
 			ret.err = onErr(ret.err)
 		}
@@ -44,11 +54,15 @@ func (b *Backend) Do(cmd Cmd) error {
 	if err != nil {
 		return b.onErr(err)
 	}
-	err = b.w.Flush()
+	err = b.bw.Flush()
 	if err != nil {
 		return b.onErr(err)
 	}
 
+	if _, ok := cmd.(CmdDone); ok {
+		return b.onErr(nil)
+	}
+
 	return nil
 }
 
-- 
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