Pillow/Tests/test_file_mic.py
Jon Dufresne 4cd4adddc3 Improve handling of file resources
Follow Python's file object semantics. User code is responsible for
closing resources (usually through a context manager) in a deterministic
way.

To achieve this, remove __del__ functions. These functions used to
closed open file handlers in an attempt to silence Python
ResourceWarnings. However, using __del__ has the following drawbacks:

- __del__ isn't called until the object's reference count reaches 0.
  Therefore, resource handlers remain open or in use longer than
  necessary.

- The __del__ method isn't guaranteed to execute on system exit. See the
  Python documentation:

  https://docs.python.org/3/reference/datamodel.html#object.__del__

  > It is not guaranteed that __del__() methods are called for objects
  > that still exist when the interpreter exits.

- Exceptions that occur inside __del__ are ignored instead of raised.
  This has the potential of hiding bugs. This is also in the Python
  documentation:

  > Warning: Due to the precarious circumstances under which __del__()
  > methods are invoked, exceptions that occur during their execution
  > are ignored, and a warning is printed to sys.stderr instead.

Instead, always close resource handlers when they are no longer in use.
This will close the file handler at a specified point in the user's code
and not wait until the interpreter chooses to. It is always guaranteed
to run. And, if an exception occurs while closing the file handler, the
bug will not be ignored.

Now, when code receives a ResourceWarning, it will highlight an area
that is mishandling resources. It should not simply be silenced, but
fixed by closing resources with a context manager.

All warnings that were emitted during tests have been cleaned up. To
enable warnings, I passed the `-Wa` CLI option to Python. This exposed
some mishandling of resources in ImageFile.__init__() and
SpiderImagePlugin.loadImageSeries(), they too were fixed.
2019-10-12 08:27:17 -07:00

64 lines
1.9 KiB
Python

from PIL import Image, ImagePalette, features
from .helper import PillowTestCase, hopper, unittest
try:
from PIL import MicImagePlugin
except ImportError:
olefile_installed = False
else:
olefile_installed = True
TEST_FILE = "Tests/images/hopper.mic"
@unittest.skipUnless(olefile_installed, "olefile package not installed")
@unittest.skipUnless(features.check("libtiff"), "libtiff not installed")
class TestFileMic(PillowTestCase):
def test_sanity(self):
with Image.open(TEST_FILE) as im:
im.load()
self.assertEqual(im.mode, "RGBA")
self.assertEqual(im.size, (128, 128))
self.assertEqual(im.format, "MIC")
# Adjust for the gamma of 2.2 encoded into the file
lut = ImagePalette.make_gamma_lut(1 / 2.2)
im = Image.merge("RGBA", [chan.point(lut) for chan in im.split()])
im2 = hopper("RGBA")
self.assert_image_similar(im, im2, 10)
def test_n_frames(self):
with Image.open(TEST_FILE) as im:
self.assertEqual(im.n_frames, 1)
def test_is_animated(self):
with Image.open(TEST_FILE) as im:
self.assertFalse(im.is_animated)
def test_tell(self):
with Image.open(TEST_FILE) as im:
self.assertEqual(im.tell(), 0)
def test_seek(self):
with Image.open(TEST_FILE) as im:
im.seek(0)
self.assertEqual(im.tell(), 0)
self.assertRaises(EOFError, im.seek, 99)
self.assertEqual(im.tell(), 0)
def test_invalid_file(self):
# Test an invalid OLE file
invalid_file = "Tests/images/flower.jpg"
self.assertRaises(SyntaxError, MicImagePlugin.MicImageFile, invalid_file)
# Test a valid OLE file, but not a MIC file
ole_file = "Tests/images/test-ole-file.doc"
self.assertRaises(SyntaxError, MicImagePlugin.MicImageFile, ole_file)