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MNT: be more careful about disk I/O failures when writing font cache #28541

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Merged
merged 1 commit into from
Jul 12, 2024
+27 −5
Merged

MNT: be more careful about disk I/O failures when writing font cache #28541

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8 changes: 4 additions & 4 deletions lib/matplotlib/font_manager.py
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Original file line number Diff line number Diff line change
Expand Up @@ -965,11 +965,11 @@ def json_dump(data, filename):
This function temporarily locks the output file to prevent multiple
processes from overwriting one another's output.
"""
with cbook._lock_path(filename), open(filename, 'w') as fh:
try:
try:
with cbook._lock_path(filename), open(filename, 'w') as fh:
json.dump(data, fh, cls=_JSONEncoder, indent=2)
except OSError as e:
_log.warning('Could not save font_manager cache %s', e)
except OSError as e:
_log.warning('Could not save font_manager cache %s', e)


def json_load(filename):
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24 changes: 23 additions & 1 deletion lib/matplotlib/tests/test_font_manager.py
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Expand Up @@ -16,7 +16,7 @@
json_dump, json_load, get_font, is_opentype_cff_font,
MSUserFontDirectories, _get_fontconfig_fonts, ttfFontProperty)
from matplotlib import cbook, ft2font, pyplot as plt, rc_context, figure as mfigure
from matplotlib.testing import subprocess_run_helper
from matplotlib.testing import subprocess_run_helper, subprocess_run_for_testing


has_fclist = shutil.which('fc-list') is not None
Expand Down Expand Up @@ -287,6 +287,28 @@ def test_fontcache_thread_safe():
subprocess_run_helper(_test_threading, timeout=10)


def test_lockfilefailure(tmp_path):
# The logic here:
# 1. get a temp directory from pytest
# 2. import matplotlib which makes sure it exists
# 3. get the cache dir (where we check it is writable)
# 4. make it not writable
# 5. try to write into it via font manager
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Suggested change
# 5. try to write into it via font manager
# 5. try to write into it via font manager
# 6. Check that we do not raise even though 5. cannot work

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Optional: Check that the log warning is emitted.

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I'm going to pass on adding a check for the logging. I don't think we do that systematically currently and because the log emission happens in the sub-process it would take a fair amount of work to check (I think something like the tests for blocking where we print something and them search for the string in stdout).

proc = subprocess_run_for_testing(
[
sys.executable,
"-c",
"import matplotlib;"
"import os;"
"p = matplotlib.get_cachedir();"
"os.chmod(p, 0o555);"
"import matplotlib.font_manager;"
],
env={**os.environ, 'MPLCONFIGDIR': str(tmp_path)},
check=True
)


def test_fontentry_dataclass():
fontent = FontEntry(name='font-name')

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