From a5d6946387efe7d64d09dcba68cdd523dc1273a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Sun, 16 Dec 2018 12:45:33 +0100
Subject: [PATCH] Return nil in CopyOnWriteFs.MkdirAll when directory exists

Fixes #191
---
 copyOnWriteFs.go      |  3 ++-
 copyOnWriteFs_test.go | 11 +++++------
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/copyOnWriteFs.go b/copyOnWriteFs.go
index f5dd237..e8108a8 100644
--- a/copyOnWriteFs.go
+++ b/copyOnWriteFs.go
@@ -282,7 +282,8 @@ func (u *CopyOnWriteFs) MkdirAll(name string, perm os.FileMode) error {
 		return u.layer.MkdirAll(name, perm)
 	}
 	if dir {
-		return ErrFileExists
+		// This is in line with how os.MkdirAll behaves.
+		return nil
 	}
 	return u.layer.MkdirAll(name, perm)
 }
diff --git a/copyOnWriteFs_test.go b/copyOnWriteFs_test.go
index a6cbc00..94ba725 100644
--- a/copyOnWriteFs_test.go
+++ b/copyOnWriteFs_test.go
@@ -36,13 +36,12 @@ func TestCopyOnWrite(t *testing.T) {
 			t.Errorf("Mkdir: Got %q for %T", err, fs)
 		}
 
-		// https://github.com/spf13/afero/issues/191
-		if _, ok := fs.(*OsFs); !ok {
-			err = fs.MkdirAll(dir, 0744)
-			if err == nil || !os.IsExist(err) {
-				t.Errorf("MkdirAll:  Got %q for %T", err, fs)
-			}
+		// MkdirAll does not return an error when the directory already exists
+		err = fs.MkdirAll(dir, 0744)
+		if err != nil {
+			t.Errorf("MkdirAll:  Got %q for %T", err, fs)
 		}
+
 	}
 }