Pillow/Tests/test_file_dcx.py

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from __future__ import annotations
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import warnings
import pytest
from PIL import DcxImagePlugin, Image
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from .helper import assert_image_equal, hopper, is_pypy
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# Created with ImageMagick: convert hopper.ppm hopper.dcx
TEST_FILE = "Tests/images/hopper.dcx"
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def test_sanity():
# Arrange
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# Act
with Image.open(TEST_FILE) as im:
# Assert
assert im.size == (128, 128)
assert isinstance(im, DcxImagePlugin.DcxImageFile)
orig = hopper()
assert_image_equal(im, orig)
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@pytest.mark.skipif(is_pypy(), reason="Requires CPython")
def test_unclosed_file():
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def open():
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im = Image.open(TEST_FILE)
im.load()
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with pytest.warns(ResourceWarning):
open()
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.
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def test_closed_file():
with warnings.catch_warnings():
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im = Image.open(TEST_FILE)
im.load()
im.close()
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.
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def test_context_manager():
with warnings.catch_warnings():
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.
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with Image.open(TEST_FILE) as im:
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im.load()
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def test_invalid_file():
with open("Tests/images/flower.jpg", "rb") as fp:
with pytest.raises(SyntaxError):
DcxImagePlugin.DcxImageFile(fp)
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def test_tell():
# Arrange
with Image.open(TEST_FILE) as im:
# Act
frame = im.tell()
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# Assert
assert frame == 0
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def test_n_frames():
with Image.open(TEST_FILE) as im:
assert im.n_frames == 1
assert not im.is_animated
def test_eoferror():
with Image.open(TEST_FILE) as im:
n_frames = im.n_frames
# Test seeking past the last frame
with pytest.raises(EOFError):
im.seek(n_frames)
assert im.tell() < n_frames
# Test that seeking to the last frame does not raise an error
im.seek(n_frames - 1)
def test_seek_too_far():
# Arrange
with Image.open(TEST_FILE) as im:
frame = 999 # too big on purpose
# Act / Assert
with pytest.raises(EOFError):
im.seek(frame)