fix multifs listdir bug (#150)

Author: willmcgugan

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [2.0.20] - 2018-03-13
+
+### Fixed
+
+- MultiFS.listdir now correctly filters out duplicates
+
 ## [2.0.19] - 2018-03-11
 
 ### Fixed

fs/_version.py

@@ -1,3 +1,3 @@
 """Version, used in module and setup.py.
 """
-__version__ = "2.0.19"
+__version__ = "2.0.20"

fs/multifs.py

@@ -5,7 +5,7 @@
 from __future__ import unicode_literals
 from __future__ import print_function
 
-from collections import namedtuple
+from collections import namedtuple, OrderedDict
 from operator import itemgetter
 
 from six import text_type
@@ -203,6 +203,7 @@ def listdir(self, path):
                 exists = True
         if not exists:
             raise errors.ResourceNotFound(path)
+        directory = list(OrderedDict.fromkeys(directory))
         return directory
 
     def makedir(self, path, permissions=None, recreate=False):

tests/test_multifs.py

@@ -134,3 +134,13 @@ def test_no_writable(self):
     def test_validate_path(self):
         self.fs.write_fs = None
         self.fs.validatepath('foo')
+
+    def test_listdir_duplicates(self):
+        m1 = MemoryFS()
+        m2 = MemoryFS()
+        m1.touch('foo')
+        m2.touch('foo')
+        multi_fs = MultiFS()
+        multi_fs.add_fs('m1', m1)
+        multi_fs.add_fs('m2', m2)
+        self.assertEqual(multi_fs.listdir(u'/'), ['foo'])