Pillow/Tests/test_file_spider.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

148 lines
3.8 KiB
Python

import tempfile
import unittest
from io import BytesIO
from PIL import Image, ImageSequence, SpiderImagePlugin
from .helper import PillowTestCase, hopper, is_pypy
TEST_FILE = "Tests/images/hopper.spider"
class TestImageSpider(PillowTestCase):
def test_sanity(self):
with Image.open(TEST_FILE) as im:
im.load()
self.assertEqual(im.mode, "F")
self.assertEqual(im.size, (128, 128))
self.assertEqual(im.format, "SPIDER")
@unittest.skipIf(is_pypy(), "Requires CPython")
def test_unclosed_file(self):
def open():
im = Image.open(TEST_FILE)
im.load()
self.assert_warning(ResourceWarning, open)
def test_closed_file(self):
def open():
im = Image.open(TEST_FILE)
im.load()
im.close()
self.assert_warning(None, open)
def test_context_manager(self):
def open():
with Image.open(TEST_FILE) as im:
im.load()
self.assert_warning(None, open)
def test_save(self):
# Arrange
temp = self.tempfile("temp.spider")
im = hopper()
# Act
im.save(temp, "SPIDER")
# Assert
with Image.open(temp) as im2:
self.assertEqual(im2.mode, "F")
self.assertEqual(im2.size, (128, 128))
self.assertEqual(im2.format, "SPIDER")
def test_tempfile(self):
# Arrange
im = hopper()
# Act
with tempfile.TemporaryFile() as fp:
im.save(fp, "SPIDER")
# Assert
fp.seek(0)
reloaded = Image.open(fp)
self.assertEqual(reloaded.mode, "F")
self.assertEqual(reloaded.size, (128, 128))
self.assertEqual(reloaded.format, "SPIDER")
def test_isSpiderImage(self):
self.assertTrue(SpiderImagePlugin.isSpiderImage(TEST_FILE))
def test_tell(self):
# Arrange
with Image.open(TEST_FILE) as im:
# Act
index = im.tell()
# Assert
self.assertEqual(index, 0)
def test_n_frames(self):
with Image.open(TEST_FILE) as im:
self.assertEqual(im.n_frames, 1)
self.assertFalse(im.is_animated)
def test_loadImageSeries(self):
# Arrange
not_spider_file = "Tests/images/hopper.ppm"
file_list = [TEST_FILE, not_spider_file, "path/not_found.ext"]
# Act
img_list = SpiderImagePlugin.loadImageSeries(file_list)
# Assert
self.assertEqual(len(img_list), 1)
self.assertIsInstance(img_list[0], Image.Image)
self.assertEqual(img_list[0].size, (128, 128))
def test_loadImageSeries_no_input(self):
# Arrange
file_list = None
# Act
img_list = SpiderImagePlugin.loadImageSeries(file_list)
# Assert
self.assertIsNone(img_list)
def test_isInt_not_a_number(self):
# Arrange
not_a_number = "a"
# Act
ret = SpiderImagePlugin.isInt(not_a_number)
# Assert
self.assertEqual(ret, 0)
def test_invalid_file(self):
invalid_file = "Tests/images/invalid.spider"
self.assertRaises(IOError, Image.open, invalid_file)
def test_nonstack_file(self):
with Image.open(TEST_FILE) as im:
self.assertRaises(EOFError, im.seek, 0)
def test_nonstack_dos(self):
with Image.open(TEST_FILE) as im:
for i, frame in enumerate(ImageSequence.Iterator(im)):
if i > 1:
self.fail("Non-stack DOS file test failed")
# for issue #4093
def test_odd_size(self):
data = BytesIO()
width = 100
im = Image.new("F", (width, 64))
im.save(data, format="SPIDER")
data.seek(0)
im2 = Image.open(data)
self.assert_image_equal(im, im2)