Extract method for resolving the 'base' for name/suffix/suffixes/stem…

… operations

Fixes #96

newsfragments/96.bugfix.rst

@@ -0,0 +1 @@
+Fixed name/suffix/suffixes/stem operations when no filename is present and the Path is not at the root of the zipfile.

tests/test_zipp.py

@@ -408,9 +408,6 @@ def test_suffixes(self, alpharep):
         e = root / '.hgrc'
         assert e.suffixes == []
 
-    import pytest
-
-    @pytest.mark.xfail(reason="96")
     @pass_alpharep
     def test_suffix_no_filename(self, alpharep):
         alpharep.filename = None

zipp/__init__.py

@@ -298,21 +298,24 @@ def open(self, mode='r', *args, pwd=None, **kwargs):
         encoding, args, kwargs = _extract_text_encoding(*args, **kwargs)
         return io.TextIOWrapper(stream, encoding, *args, **kwargs)
 
+    def _base(self):
+        return pathlib.Path(self.at) if self.at else self.filename
+
     @property
     def name(self):
-        return pathlib.Path(self.at).name or self.filename.name
+        return self._base().name
 
     @property
     def suffix(self):
-        return pathlib.Path(self.at).suffix or self.filename.suffix
+        return self._base().suffix
 
     @property
     def suffixes(self):
-        return pathlib.Path(self.at).suffixes or self.filename.suffixes
+        return self._base().suffixes
 
     @property
     def stem(self):
-        return pathlib.Path(self.at).stem or self.filename.stem
+        return self._base().stem
 
     @property
     def filename(self):