Use Windows path rules to parse ZipFile.filename on Windows

Fixes #133

Author: barneygale

newsfragments/133.bugfix.rst

@@ -0,0 +1 @@
+Use Windows path rules to parse ``ZipFile.filename`` on Windows

tests/test_path.py

@@ -356,6 +356,7 @@ def test_root_name(self, alpharep):
         """
         The name of the root should be the name of the zipfile
         """
+        alpharep = self.zipfile_ondisk(alpharep)
         root = zipfile.Path(alpharep)
         assert root.name == 'alpharep.zip' == root.filename.name
 
@@ -412,6 +413,7 @@ def test_stem(self, alpharep):
         """
         The final path component, without its suffix
         """
+        alpharep = self.zipfile_ondisk(alpharep)
         root = zipfile.Path(alpharep)
         assert root.stem == 'alpharep' == root.filename.stem
 

zipp/__init__.py

@@ -356,7 +356,10 @@ def open(self, mode='r', *args, pwd=None, **kwargs):
         return io.TextIOWrapper(stream, encoding, *args, **kwargs)
 
     def _base(self):
-        return pathlib.PurePosixPath(self.at or self.root.filename)
+        if self.at:
+            return pathlib.PurePosixPath(self.at)
+        else:
+            return pathlib.PurePath(self.root.filename)
 
     @property
     def name(self):