matplotlib · QuLogic · Jan 30, 2025 · Jan 30, 2025 · Feb 11, 2025 · Feb 11, 2025
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
@@ -56,10 +56,11 @@ jobs:
             pygobject-ver: '<3.52.0'
           - os: ubuntu-22.04
             python-version: '3.11'
-            CFLAGS: "-fno-lto"  # Ensure that disabling LTO works.
+            lto: "--config-settings=setup-args=-Db_lto=false"  # Ensure that disabling LTO works.
             extra-requirements: '-r requirements/testing/extra.txt'
             # https://github.com/matplotlib/matplotlib/issues/29844
             pygobject-ver: '<3.52.0'
+            python-optimize: 'true'
           - os: ubuntu-22.04-arm
             python-version: '3.12'
             # https://github.com/matplotlib/matplotlib/issues/29844
@@ -317,7 +318,7 @@ jobs:
           fi
 
           python -m pip install --no-deps --no-build-isolation --verbose \
-            --config-settings=setup-args="-DrcParams-backend=Agg" \
+            --config-settings=setup-args="-DrcParams-backend=Agg" ${{ matrix.lto }} \
             --editable .[dev]
 
           if [[ "${{ runner.os }}" != 'macOS' ]]; then
@@ -334,7 +335,10 @@ jobs:
           if [[ "${{ matrix.python-version }}" == '3.13t' ]]; then
             export PYTHON_GIL=0
           fi
-          pytest -rfEsXR -n auto \
+          if [[ "${{ matrix.python-optimize }}" == 'true' ]]; then
+            export PYTHONOPTIMIZE=2
+          fi
+          pytest -rfEsXR -n auto -sv \
             --maxfail=50 --timeout=300 --durations=25 \
             --cov-report=xml --cov=lib --log-level=DEBUG --color=yes
 

diff --git a/lib/matplotlib/testing/__init__.py b/lib/matplotlib/testing/__init__.py
@@ -129,6 +129,8 @@ def subprocess_run_helper(func, *args, timeout, extra_env=None):
         [
             sys.executable,
             "-c",
+            f"import pytest;"
+            f"pytest.register_assert_rewrite({module!r});"
             f"import importlib.util;"
             f"_spec = importlib.util.spec_from_file_location({module!r}, {file!r});"
             f"_module = importlib.util.module_from_spec(_spec);"

diff --git a/lib/matplotlib/tests/test_artist.py b/lib/matplotlib/tests/test_artist.py
@@ -1,5 +1,6 @@
 import io
 from itertools import chain
+import sys
 
 import numpy as np
 
@@ -256,7 +257,9 @@ def test_setp():
     # Check *file* argument
     sio = io.StringIO()
     plt.setp(lines1, 'zorder', file=sio)
-    assert sio.getvalue() == '  zorder: float\n'
+    # With optimization, docstrings are stripped so the automated types don't work.
+    expected = 'unknown' if sys.flags.optimize >= 2 else 'float'
+    assert sio.getvalue() == f'  zorder: {expected}\n'
 
 
 def test_None_zorder():
@@ -361,6 +364,8 @@ def set_myparam2(self, val):
     assert 'myparam2' in MyArtist2.set.__doc__
 
 
+@pytest.mark.skipif(sys.flags.optimize >= 2,
+                    reason='Python optimization is enabled and docstrings are stripped')
 def test_set_is_overwritten():
     """set() defined in Artist subclasses should not be overwritten."""
     class MyArtist3(martist.Artist):

diff --git a/lib/matplotlib/tests/test_backends_interactive.py b/lib/matplotlib/tests/test_backends_interactive.py
@@ -460,6 +460,8 @@
     reason="$DISPLAY and $WAYLAND_DISPLAY are unset")
 @pytest.mark.parametrize('host, mpl', [*qt5_and_qt6_pairs()])
 def test_cross_Qt_imports(host, mpl):
+    if sys.flags.optimize > 0 and 'PySide2' in {host, mpl}:
+        pytest.xfail('PySide2 does not work optimized')
     try:
         proc = _run_helper(_impl_test_cross_Qt_imports, host, mpl,
                            timeout=_test_timeout)

diff --git a/lib/matplotlib/tests/test_matplotlib.py b/lib/matplotlib/tests/test_matplotlib.py
@@ -44,6 +44,8 @@ def test_importable_with_no_home(tmp_path):
         env={**os.environ, "MPLCONFIGDIR": str(tmp_path)}, check=True)
 
 
+@pytest.mark.skipif(sys.flags.optimize >= 2,
+                    reason='Python optimization is enabled and docstrings are stripped')
 def test_use_doc_standard_backends():
     """
     Test that the standard backends mentioned in the docstring of

diff --git a/lib/matplotlib/tests/test_preprocess_data.py b/lib/matplotlib/tests/test_preprocess_data.py
@@ -39,23 +39,25 @@ def func_no_ax_args(*args, **kwargs): pass
     # this has "enough" information to do all the replaces
     _preprocess_data(replace_names=["x", "y"])(func_args)
 
-    # no positional_parameter_names but needed due to replaces
-    with pytest.raises(AssertionError):
-        # z is unknown
-        _preprocess_data(replace_names=["x", "y", "z"])(func_args)
-
     # no replacements at all -> all ok...
     _preprocess_data(replace_names=[], label_namer=None)(func)
     _preprocess_data(replace_names=[], label_namer=None)(func_args)
     _preprocess_data(replace_names=[], label_namer=None)(func_kwargs)
     _preprocess_data(replace_names=[], label_namer=None)(func_no_ax_args)
 
-    # label namer is unknown
-    with pytest.raises(AssertionError):
-        _preprocess_data(label_namer="z")(func)
+    # No asserts with optimizations.
+    if sys.flags.optimize < 1:
+        # no positional_parameter_names but needed due to replaces
+        with pytest.raises(AssertionError):
+            # z is unknown
+            _preprocess_data(replace_names=["x", "y", "z"])(func_args)
+
+        # label namer is unknown
+        with pytest.raises(AssertionError):
+            _preprocess_data(label_namer="z")(func)
 
-    with pytest.raises(AssertionError):
-        _preprocess_data(label_namer="z")(func_args)
+        with pytest.raises(AssertionError):
+            _preprocess_data(label_namer="z")(func_args)
 
 
 @pytest.mark.parametrize('func', all_funcs, ids=all_func_ids)
@@ -193,6 +195,8 @@ def func(ax, x, y, z=1):
         func(None, "a", "b", "z", "z", data=data)
 
 
+@pytest.mark.skipif(sys.flags.optimize >= 2,
+                    reason='Python optimization is enabled and docstrings are stripped')
 def test_docstring_addition():
     @_preprocess_data()
     def funcy(ax, *args, **kwargs):