From 78b8794821e93f625e6d07896b7cfd771ff23fd0 Mon Sep 17 00:00:00 2001
From: Daniel Hahler <github@thequod.de>
Date: Fri, 22 Feb 2019 01:58:45 +0100
Subject: [PATCH] path.local: as_cwd: do not chdir to None (#215)

---
 CHANGELOG                  |  3 +++
 py/_path/local.py          |  9 ++++++---
 testing/path/test_local.py | 13 +++++++++++++
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 94c06345..ed60b0a0 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -4,6 +4,9 @@
 - add ``"importlib"`` pyimport mode for python3.5+, allowing unimportable test suites
   to contain identically named modules.
 
+- fix ``LocalPath.as_cwd()`` not calling ``os.chdir()`` with ``None``, when
+  being invoked from a non-existing directory.
+
 1.7.0 (2018-10-11)
 ==================
 
diff --git a/py/_path/local.py b/py/_path/local.py
index 3ac31945..0e856a66 100644
--- a/py/_path/local.py
+++ b/py/_path/local.py
@@ -579,14 +579,17 @@ def chdir(self):
 
     @contextmanager
     def as_cwd(self):
-        """ return context manager which changes to current dir during the
-        managed "with" context. On __enter__ it returns the old dir.
+        """
+        Return a context manager, which changes to the path's dir during the
+        managed "with" context.
+        On __enter__ it returns the old dir, which might be ``None``.
         """
         old = self.chdir()
         try:
             yield old
         finally:
-            old.chdir()
+            if old is not None:
+                old.chdir()
 
     def realpath(self):
         """ return a new path which contains no symbolic links."""
diff --git a/testing/path/test_local.py b/testing/path/test_local.py
index 2b8519c5..d52409e5 100644
--- a/testing/path/test_local.py
+++ b/testing/path/test_local.py
@@ -125,6 +125,19 @@ def test_chdir_gone(self, path1):
         assert path1.chdir() is None
         assert os.getcwd() == str(path1)
 
+        with pytest.raises(py.error.ENOENT):
+            with p.as_cwd():
+                raise NotImplementedError
+
+    @skiponwin32
+    def test_chdir_gone_in_as_cwd(self, path1):
+        p = path1.ensure("dir_to_be_removed", dir=1)
+        p.chdir()
+        p.remove()
+
+        with path1.as_cwd() as old:
+            assert old is None
+
     def test_as_cwd(self, path1):
         dir = path1.ensure("subdir", dir=1)
         old = py.path.local()