#17616: Improve context manager tests, fix bugs in close method and mode docs.

'mode' docs fix: the file must always be opened in binary in Python3.

Bug in Wave_write.close: when the close method calls the check that the header
exists and it raises an error, the _file attribute never gets set to None, so
the next close tries to close the file again and we get an ignored traceback
in the __del__ method.  The fix is to set _file to None in a finally clause.
This represents a behavior change...in theory a program could be checking for
the error on close and then doing a recovery action on the still open file and
closing it again.  But this change will only go into 3.4, so I think that
behavior change is acceptable given that it would be pretty weird and unlikely
logic to begin with.

Doc/library/wave.rst

@@ -19,21 +19,20 @@ The :mod:`wave` module defines the following function and exception:
 .. function:: open(file, mode=None)
 
    If *file* is a string, open the file by that name, otherwise treat it as a
-   seekable file-like object.  *mode* can be any of
+   seekable file-like object.  *mode* can be:
 
-   ``'r'``, ``'rb'``
+   ``'rb'``
       Read only mode.
 
-   ``'w'``, ``'wb'``
+   ``'wb'``
       Write only mode.
 
    Note that it does not allow read/write WAV files.
 
-   A *mode* of ``'r'`` or ``'rb'`` returns a :class:`Wave_read` object, while a
-   *mode* of ``'w'`` or ``'wb'`` returns a :class:`Wave_write` object.  If
-   *mode* is omitted and a file-like object is passed as *file*, ``file.mode``
-   is used as the default value for *mode* (the ``'b'`` flag is still added if
-   necessary).
+   A *mode* of ``'rb'`` returns a :class:`Wave_read` object, while a *mode* of
+   ``'wb'`` returns a :class:`Wave_write` object.  If *mode* is omitted and a
+   file-like object is passed as *file*, ``file.mode`` is used as the default
+   value for *mode*.
 
    If you pass in a file-like object, the wave object will not close it when its
    :meth:`close` method is called; it is the caller's responsibility to close

Lib/test/test_wave.py

@@ -69,22 +69,49 @@ class TestWave(unittest.TestCase):
         self.assertEqual(params.comptype, self.f.getcomptype())
         self.assertEqual(params.compname, self.f.getcompname())
 
-    def test_context_manager(self):
-        self.f = wave.open(TESTFN, 'wb')
-        self.f.setnchannels(nchannels)
-        self.f.setsampwidth(sampwidth)
-        self.f.setframerate(framerate)
-        self.f.close()
+    def test_wave_write_context_manager_calls_close(self):
+        # Close checks for a minimum header and will raise an error
+        # if it is not set, so this proves that close is called.
+        with self.assertRaises(wave.Error):
+            with wave.open(TESTFN, 'wb') as f:
+                pass
+        print('in test:', f._file)
+        with self.assertRaises(wave.Error):
+            with open(TESTFN, 'wb') as testfile:
+                with wave.open(testfile):
+                    pass
 
-        with wave.open(TESTFN) as f:
+    def test_context_manager_with_open_file(self):
+        with open(TESTFN, 'wb') as testfile:
+            with wave.open(testfile) as f:
+                f.setnchannels(nchannels)
+                f.setsampwidth(sampwidth)
+                f.setframerate(framerate)
+            self.assertFalse(testfile.closed)
+        with open(TESTFN, 'rb') as testfile:
+            with wave.open(testfile) as f:
                 self.assertFalse(f.getfp().closed)
-        self.assertIs(f.getfp(), None)
+                params = f.getparams()
+                self.assertEqual(params.nchannels, nchannels)
+                self.assertEqual(params.sampwidth, sampwidth)
+                self.assertEqual(params.framerate, framerate)
+            self.assertIsNone(f.getfp())
+            self.assertFalse(testfile.closed)
 
-        with open(TESTFN, 'wb') as testfile:
-            with self.assertRaises(wave.Error):
-                with wave.open(testfile, 'wb'):
-                    pass
-            self.assertEqual(testfile.closed, False)
+    def test_context_manager_with_filename(self):
+        # If the file doesn't get closed, this test won't fail, but it will
+        # produce a resource leak warning.
+        with wave.open(TESTFN, 'wb') as f:
+            f.setnchannels(nchannels)
+            f.setsampwidth(sampwidth)
+            f.setframerate(framerate)
+        with wave.open(TESTFN) as f:
+            self.assertFalse(f.getfp().closed)
+            params = f.getparams()
+            self.assertEqual(params.nchannels, nchannels)
+            self.assertEqual(params.sampwidth, sampwidth)
+            self.assertEqual(params.framerate, framerate)
+        self.assertIsNone(f.getfp())
 
 
 if __name__ == '__main__':

Lib/wave.py

@@ -448,10 +448,12 @@ class Wave_write:
 
     def close(self):
         if self._file:
+            try:
                 self._ensure_header_written(0)
                 if self._datalength != self._datawritten:
                     self._patchheader()
                 self._file.flush()
+            finally:
                 self._file = None
         if self._i_opened_the_file:
             self._i_opened_the_file.close()