Change errorhandling once again

untitaker · untitaker · commit d27b02050ec9 · 2015-02-08T14:40:19.000+01:00
diff --git a/atomicwrites/__init__.py b/atomicwrites/__init__.py
@@ -9,30 +9,18 @@
 
 PY2 = sys.version_info[0] == 2
 
-if PY2:
-    class FileExistsError(OSError):
-        errno = errno.EEXIST
 
-    class FileNotFoundError(OSError):
-        errno = errno.ENOENT
-else:
-    # For some reason we have to redefine this, or users can't import it.
-    FileExistsError = FileExistsError
-    FileNotFoundError = FileNotFoundError
+class _FileExistsError(OSError if PY2 else FileExistsError):
+    errno = errno.EEXIST
+
+class _FileNotFoundError(OSError if PY2 else FileNotFoundError):
+    errno = errno.ENOENT
 
 
 if sys.platform != 'win32':
     @contextlib.contextmanager
     def handle_errors():
-        try:
-            yield
-        except FileExistsError:
-            raise
-        except OSError as e:
-            if e.errno == errno.EEXIST:
-                raise FileExistsError(str(e))
-            else:
-                raise
+        yield
 
     def _replace_atomic(src, dst):
         os.rename(src, dst)
@@ -47,20 +35,19 @@ def _move_atomic(src, dst):
 
     _windows_default_flags = win32file.MOVEFILE_WRITE_THROUGH
     _windows_error_table = {
-        183: FileExistsError,
-        3: FileNotFoundError
+        183: _FileExistsError,
+        3: _FileNotFoundError
     }
 
     @contextlib.contextmanager
     def handle_errors():
         try:
             yield
         except pywintypes.error as e:
-            native_cls = _windows_error_table.get(e.winerror, None)
-            if native_cls is not None:
-                raise native_cls(str(e))
-            else:
-                raise
+            native_cls = _windows_error_table.get(e.winerror, OSError)
+            new_e = native_cls(e)
+            new_e.windows_error = e
+            raise new_e
 
     def _replace_atomic(src, dst):
         win32api.MoveFileEx(
diff --git a/docs/index.rst b/docs/index.rst
@@ -8,8 +8,15 @@ API
 .. autofunction:: atomic_write
 
 
-Exceptions
-----------
+Errorhandling
+-------------
+
+All filesystem errors are subclasses of :py:exc:`OSError`.
+
+- On UNIX systems, errors from the Python stdlib calls are simply uncaught.
+- On Windows systems, some PyWin32 errors are intercepted such that they
+  resemble the stdlib exceptions. The original PyWin32 exception object is
+  available as ``windows_error`` at all times.
 
 .. exception:: FileExistsError
 
diff --git a/tests/test_atomicwrites.py b/tests/test_atomicwrites.py
@@ -1,4 +1,6 @@
-from atomicwrites import atomic_write, FileExistsError
+import errno
+
+from atomicwrites import atomic_write
 
 import pytest
 
@@ -9,10 +11,12 @@ def test_atomic_write(tmpdir):
         with atomic_write(str(fname), overwrite=True) as f:
             f.write('hoho')
 
-    with pytest.raises(FileExistsError):
+    with pytest.raises(OSError) as excinfo:
         with atomic_write(str(fname), overwrite=False) as f:
             f.write('haha')
 
+    assert excinfo.value.errno == errno.EEXIST
+
     assert fname.read() == 'hoho'
     assert len(tmpdir.listdir()) == 1
 
@@ -38,10 +42,12 @@ def test_replace_simultaneously_created_file(tmpdir):
 
 def test_dont_remove_simultaneously_created_file(tmpdir):
     fname = tmpdir.join('ha')
-    with pytest.raises(FileExistsError):
+    with pytest.raises(OSError) as excinfo:
         with atomic_write(str(fname), overwrite=False) as f:
             f.write('hoho')
             fname.write('harhar')
             assert fname.read() == 'harhar'
+
+    assert excinfo.value.errno == errno.EEXIST
     assert fname.read() == 'harhar'
     assert len(tmpdir.listdir()) == 1
