bpo-26175: Fix SpooledTemporaryFile IOBase abstract

Doc/library/tempfile.rst

@@ -116,6 +116,7 @@ The module defines the following user-callable items:
 
  .. versionchanged:: 3.8
  Added *errors* parameter.
+ Implemented :class:`io.IOBase` inteface.
 
 
 .. function:: TemporaryDirectory(suffix=None, prefix=None, dir=None)

Lib/tempfile.py

@@ -620,7 +620,7 @@ def TemporaryFile(mode='w+b', buffering=-1, encoding=None,
  _os.close(fd)
  raise
 
-class SpooledTemporaryFile:
+class SpooledTemporaryFile(_io.IOBase):
  """Temporary file wrapper, specialized to switch from BytesIO
  or StringIO to a real file when it exceeds a certain size or
  when a fileno is needed.
@@ -679,6 +679,9 @@ def __exit__(self, exc, value, tb):
  def __iter__(self):
  return self._file.__iter__()
 
+ def __del__(self):
+ return self._file.__del__()
+
  def close(self):
  self._file.close()
 
@@ -725,14 +728,23 @@ def newlines(self):
  def read(self, *args):
  return self._file.read(*args)
 
+ def readable(self):
+ return self._file.readable()
+
+ def readinto(self, b):
+ return self._file.readinto(b)
+
  def readline(self, *args):
  return self._file.readline(*args)
 
  def readlines(self, *args):
  return self._file.readlines(*args)
 
  def seek(self, *args):
- self._file.seek(*args)
+ return self._file.seek(*args)
+
+ def seekable(self):
+ return self._file.seekable()
 
  @property
  def softspace(self):
@@ -743,18 +755,21 @@ def tell(self):
 
  def truncate(self, size=None):
  if size is None:
- self._file.truncate()
+return self._file.truncate()
  else:
  if size > self._max_size:
  self.rollover()
- self._file.truncate(size)
+return self._file.truncate(size)
 
  def write(self, s):
  file = self._file
  rv = file.write(s)
  self._check(file)
  return rv
 
+ def writable(self):
+ return self._file.writable()
+
  def writelines(self, iterable):
  file = self._file
  rv = file.writelines(iterable)

Lib/test/test_tempfile.py

@@ -985,6 +985,22 @@ def test_basic(self):
  f = self.do_create(max_size=100, pre="a", suf=".txt")
  self.assertFalse(f._rolled)
 
+ def test_is_iobase(self):
+ # SpooledTemporaryFile should implement io.IOBase
+ self.assertIsInstance(self.do_create(), io.IOBase)
+
+ def test_iobase_interface(self):
+ # SpooledTemporaryFile should implement the io.IOBase interface.
+ # IOBase does not declare read(), readinto(), or write(), but
+ # they should be considered part of the interface.
+ iobase_abstract = {'read', 'readinto', 'write'}
+ spooledtempfile_abstract = set(dir(tempfile.SpooledTemporaryFile))
+ missing_attributes = iobase_abstract - spooledtempfile_abstract
+ self.assertFalse(
+ missing_attributes,
+ 'io.IOBase attributes missing from SpooledTemporaryFile'
+ )
+
  def test_del_on_close(self):
  # A SpooledTemporaryFile is deleted when closed
  dir = tempfile.mkdtemp()
@@ -1000,6 +1016,21 @@ def test_del_on_close(self):
  finally:
  os.rmdir(dir)
 
+ def test_del_rolled_file(self):
+ # The rolled file should be deleted when the
+ # SpooledTemporaryFile object is deleted. This should raise a
+ # ResourceWarning since the file was not explicitly closed.
+ f = self.do_create(max_size=2)
+ f.write(b'foo')
+ filename = f.name
+ self.assertTrue(os.path.exists(filename))
+ with self.assertWarns(ResourceWarning):
+ f.__del__()
+ self.assertFalse(
+ os.path.exists(filename),
+ "Rolled SpooledTemporaryFile not deleted after __del__"
+ )
+
  def test_rewrite_small(self):
  # A SpooledTemporaryFile can be written to multiple within the max_size
  f = self.do_create(max_size=30)

Misc/NEWS.d/next/Library/2017-08-30-23-14-17.bpo-26175.GOaj9y.rst

@@ -0,0 +1,2 @@
+Fully implement io.IOBase interface for tempfile.SpooledTemporaryFile.
+Patch by Gary Fernie.