MNT: hoist latex helpers from pgf tests to matplotlib.testing

Move the marks to skip if various latex installs are missing to be
visible on other modules.

Author: tacaswell

lib/matplotlib/backends/backend_ps.py

@@ -1133,6 +1133,7 @@ def draw(self):
         _no_output_draw(self.figure)
         return super().draw()
 
+
 def convert_psfrags(tmpfile, psfrags, font_preamble, custom_preamble,
                     paper_width, paper_height, orientation):
     """

lib/matplotlib/testing/__init__.py

@@ -4,6 +4,9 @@
 
 import locale
 import logging
+import subprocess
+from pathlib import Path
+from tempfile import TemporaryDirectory
 
 import matplotlib as mpl
 from matplotlib import _api
@@ -44,3 +47,31 @@ def setup():
     # are not necessarily the default values as specified in rcsetup.py.
     set_font_settings_for_testing()
     set_reproducibility_for_testing()
+
+
+def check_for_pgf(texsystem):
+    """
+    Check if a given TeX system + pgf is available
+
+    Parameters
+    ----------
+    texsystem : str
+        The executable name to check
+    """
+    with TemporaryDirectory() as tmpdir:
+        tex_path = Path(tmpdir, "test.tex")
+        tex_path.write_text(r"""
+            \documentclass{minimal}
+            \usepackage{pgf}
+            \begin{document}
+            \typeout{pgfversion=\pgfversion}
+            \makeatletter
+            \@@end
+        """)
+        try:
+            subprocess.check_call(
+                [texsystem, "-halt-on-error", str(tex_path)], cwd=tmpdir,
+                stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        except (OSError, subprocess.CalledProcessError):
+            return False
+        return True

lib/matplotlib/tests/test_backend_bases.py

@@ -1,5 +1,6 @@
 import re
 
+from matplotlib.testing import check_for_pgf
 from matplotlib.backend_bases import (
     FigureCanvasBase, LocationEvent, MouseButton, MouseEvent,
     NavigationToolbar2, RendererBase)
@@ -13,6 +14,9 @@
 import numpy as np
 import pytest
 
+needs_xelatex = pytest.mark.skipif(not check_for_pgf('xelatex'),
+                                   reason='xelatex + pgf is required')
+
 
 def test_uses_per_path():
     id = transforms.Affine2D()
@@ -189,7 +193,9 @@ def test_toolbar_zoompan():
     assert ax.get_navigate_mode() == "PAN"
 
 
-@pytest.mark.parametrize("backend", ['svg', 'pgf', 'ps', 'pdf'])
+@pytest.mark.parametrize(
+    "backend", ['svg', 'ps', 'pdf', pytest.param('pgf', marks=needs_xelatex)]
+)
 def test_draw(backend):
     from matplotlib.figure import Figure
     from matplotlib.backends.backend_agg import FigureCanvas

lib/matplotlib/tests/test_backend_pgf.py

@@ -1,16 +1,15 @@
 import datetime
 from io import BytesIO
 import os
-from pathlib import Path
 import shutil
 import subprocess
-from tempfile import TemporaryDirectory
 
 import numpy as np
 import pytest
 
 import matplotlib as mpl
 import matplotlib.pyplot as plt
+from matplotlib.testing import check_for_pgf
 from matplotlib.testing.compare import compare_images, ImageComparisonFailure
 from matplotlib.backends.backend_pgf import PdfPages, common_texification
 from matplotlib.testing.decorators import (_image_directories,
@@ -19,32 +18,11 @@
 
 baseline_dir, result_dir = _image_directories(lambda: 'dummy func')
 
-
-def check_for(texsystem):
-    with TemporaryDirectory() as tmpdir:
-        tex_path = Path(tmpdir, "test.tex")
-        tex_path.write_text(r"""
-            \documentclass{minimal}
-            \usepackage{pgf}
-            \begin{document}
-            \typeout{pgfversion=\pgfversion}
-            \makeatletter
-            \@@end
-        """)
-        try:
-            subprocess.check_call(
-                [texsystem, "-halt-on-error", str(tex_path)], cwd=tmpdir,
-                stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
-        except (OSError, subprocess.CalledProcessError):
-            return False
-        return True
-
-
-needs_xelatex = pytest.mark.skipif(not check_for('xelatex'),
+needs_xelatex = pytest.mark.skipif(not check_for_pgf('xelatex'),
                                    reason='xelatex + pgf is required')
-needs_pdflatex = pytest.mark.skipif(not check_for('pdflatex'),
+needs_pdflatex = pytest.mark.skipif(not check_for_pgf('pdflatex'),
                                     reason='pdflatex + pgf is required')
-needs_lualatex = pytest.mark.skipif(not check_for('lualatex'),
+needs_lualatex = pytest.mark.skipif(not check_for_pgf('lualatex'),
                                     reason='lualatex + pgf is required')
 needs_ghostscript = pytest.mark.skipif(
     "eps" not in mpl.testing.compare.converter,
@@ -341,7 +319,7 @@ def test_unknown_font(caplog):
 @pytest.mark.parametrize("texsystem", ("pdflatex", "xelatex", "lualatex"))
 @pytest.mark.backend("pgf")
 def test_minus_signs_with_tex(fig_test, fig_ref, texsystem):
-    if not check_for(texsystem):
+    if not check_for_pgf(texsystem):
         pytest.skip(texsystem + ' + pgf is required')
     mpl.rcParams["pgf.texsystem"] = texsystem
     fig_test.text(.5, .5, "$-1$")