From 593752ee622157e3140babbcd50e61626ce1a7d2 Mon Sep 17 00:00:00 2001
From: Jille Timmermans <jille@quis.cx>
Date: Sun, 6 Feb 2022 11:23:13 +0100
Subject: [PATCH] Handle errors from closing writable Files

Close might do some flushing, so failures to Close might cause data loss.
---
 go.mod       |  1 +
 go.sum       |  2 ++
 unionFile.go |  8 ++++++--
 util.go      | 13 +++++++------
 4 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/go.mod b/go.mod
index b77ae414..d3397756 100644
--- a/go.mod
+++ b/go.mod
@@ -2,6 +2,7 @@ module github.com/spf13/afero
 
 require (
 	cloud.google.com/go/storage v1.14.0
+	github.com/Jille/errchain v1.0.0
 	github.com/googleapis/google-cloud-go-testing v0.0.0-20200911160855-bcd43fbb19e8
 	github.com/pkg/sftp v1.13.1
 	golang.org/x/crypto v0.0.0-20211108221036-ceb1ce70b4fa
diff --git a/go.sum b/go.sum
index 1f24646a..5f06d395 100644
--- a/go.sum
+++ b/go.sum
@@ -40,6 +40,8 @@ cloud.google.com/go/storage v1.14.0/go.mod h1:GrKmX003DSIwi9o29oFT7YDnHYwZoctc3f
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
+github.com/Jille/errchain v1.0.0 h1:S1YDbLdKAADkE1Rbj7A6d0QeoWZIvMzTBeoKjEkw9LA=
+github.com/Jille/errchain v1.0.0/go.mod h1:XaSP9ruaReMvv1BmcI52KV4NCmjVFTxjMGmKX9ixzG8=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
 github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
diff --git a/unionFile.go b/unionFile.go
index 34f99a40..ef815633 100644
--- a/unionFile.go
+++ b/unionFile.go
@@ -5,6 +5,8 @@ import (
 	"os"
 	"path/filepath"
 	"syscall"
+
+	"github.com/Jille/errchain"
 )
 
 // The UnionFile implements the afero.File interface and will be returned
@@ -32,11 +34,13 @@ func (f *UnionFile) Close() error {
 	// first close base, so we have a newer timestamp in the overlay. If we'd close
 	// the overlay first, we'd get a cacheStale the next time we access this file
 	// -> cache would be useless ;-)
+	var err error
 	if f.Base != nil {
-		f.Base.Close()
+		errchain.Append(&err, f.Base.Close())
 	}
 	if f.Layer != nil {
-		return f.Layer.Close()
+		errchain.Append(&err, f.Layer.Close())
+		return err
 	}
 	return BADFD
 }
diff --git a/util.go b/util.go
index 4f253f48..8f6055f0 100644
--- a/util.go
+++ b/util.go
@@ -25,6 +25,7 @@ import (
 	"strings"
 	"unicode"
 
+	"github.com/Jille/errchain"
 	"golang.org/x/text/transform"
 	"golang.org/x/text/unicode/norm"
 )
@@ -37,12 +38,12 @@ func (a Afero) WriteReader(path string, r io.Reader) (err error) {
 	return WriteReader(a.Fs, path, r)
 }
 
-func WriteReader(fs Fs, path string, r io.Reader) (err error) {
+func WriteReader(fs Fs, path string, r io.Reader) (retErr error) {
 	dir, _ := filepath.Split(path)
 	ospath := filepath.FromSlash(dir)
 
 	if ospath != "" {
-		err = fs.MkdirAll(ospath, 0777) // rwx, rw, r
+		err := fs.MkdirAll(ospath, 0777) // rwx, rw, r
 		if err != nil {
 			if err != os.ErrExist {
 				return err
@@ -54,7 +55,7 @@ func WriteReader(fs Fs, path string, r io.Reader) (err error) {
 	if err != nil {
 		return
 	}
-	defer file.Close()
+	defer errchain.Call(&retErr, file.Close)
 
 	_, err = io.Copy(file, r)
 	return
@@ -65,12 +66,12 @@ func (a Afero) SafeWriteReader(path string, r io.Reader) (err error) {
 	return SafeWriteReader(a.Fs, path, r)
 }
 
-func SafeWriteReader(fs Fs, path string, r io.Reader) (err error) {
+func SafeWriteReader(fs Fs, path string, r io.Reader) (retErr error) {
 	dir, _ := filepath.Split(path)
 	ospath := filepath.FromSlash(dir)
 
 	if ospath != "" {
-		err = fs.MkdirAll(ospath, 0777) // rwx, rw, r
+		err := fs.MkdirAll(ospath, 0777) // rwx, rw, r
 		if err != nil {
 			return
 		}
@@ -88,7 +89,7 @@ func SafeWriteReader(fs Fs, path string, r io.Reader) (err error) {
 	if err != nil {
 		return
 	}
-	defer file.Close()
+	defer errchain.Call(&retErr, file.Close)
 
 	_, err = io.Copy(file, r)
 	return