When latex fails, make sure it does not write a dvi.

anntzer · anntzer · commit c81bb9d4f0c6 · 2018-01-30T00:07:23.000-08:00
PR 10180 added some tests checking that when the latex subprocess used by usetex fails, a RuntimeError does propagate up to the Python process. It originally passed the CI, but since its merge, various CIs have been failing on the test that a text with `$22_2_2$` (an invalid tex construct) fails when usetex is set. This is because while `latex --interaction=nonstopmode` does exit with error code 1 when processing a file with that construct, the error is "benign" enough that it still writes a dvi before exiting (the contents are simply as if the input was `$22_{22}$`). The dvi goes into the tex cache and later CI runs pick up the cached dvi instead of running the subprocess, thus failing the test. The solution is to use --halt-on-error on top of nonstopmode, see e.g. https://tex.stackexchange.com/questions/258814/what-is-the-difference-between-interaction-nonstopmode-and-halt-on-error (and to clear your tex cache). Note that before the PR, there would similarly be the weird behavior (for the user) that the first attempt to use a "benignly" invalid tex construct would trigger an exception, but latter attempts would not (for the same reason as above).
diff --git a/lib/matplotlib/texmanager.py b/lib/matplotlib/texmanager.py
@@ -361,7 +361,8 @@ def make_dvi(self, tex, fontsize):
             texfile = self.make_tex(tex, fontsize)
             with Locked(self.texcache):
                 self._run_checked_subprocess(
-                    ["latex", "-interaction=nonstopmode", texfile], tex)
+                    ["latex", "-interaction=nonstopmode", "--halt-on-error",
+                     texfile], tex)
             for fname in glob.glob(basefile + '*'):
                 if not fname.endswith(('dvi', 'tex')):
                     try:
@@ -387,7 +388,8 @@ def make_dvi_preview(self, tex, fontsize):
         if not os.path.exists(dvifile) or not os.path.exists(baselinefile):
             texfile = self.make_tex_preview(tex, fontsize)
             report = self._run_checked_subprocess(
-                ["latex", "-interaction=nonstopmode", texfile], tex)
+                ["latex", "-interaction=nonstopmode", "--halt-on-error",
+                 texfile], tex)
 
             # find the box extent information in the latex output
             # file and store them in ".baseline" file
