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.