Pretty-format subprocess logs.

anntzer · anntzer · commit 06a91061566d · 2019-04-25T22:52:24.000+02:00
e.g. subprocess spawned by the animation machinery are now logged as
```
MovieWriter._run: running command: ffmpeg -f rawvideo -vcodec rawvideo -s 640x480 -pix_fmt rgba -r 20.0 -i pipe: -vcodec h264 -pix_fmt yuv420p -y movie.mp4
```
instead of
```
MovieWriter.run: running command: ['ffmpeg', '-f', 'rawvideo', '-vcodec', 'rawvideo', '-s', '640x480', '-pix_fmt', 'rgba', '-r', '20.0', '-i', 'pipe:', '-vcodec', 'h264', '-pix_fmt', 'yuv420p', '-y', 'movie.mp4']
```
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -354,7 +354,8 @@ def _run(self):
         # movie file.  *args* returns the sequence of command line arguments
         # from a few configuration options.
         command = self._args()
-        _log.info('MovieWriter.run: running command: %s', command)
+        _log.info('MovieWriter._run: running command: %s',
+                  cbook._pformat_subprocess(command))
         PIPE = subprocess.PIPE
         self._proc = subprocess.Popen(
             command, stdin=PIPE, stdout=PIPE, stderr=PIPE,
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -19,6 +19,7 @@
 import os
 from pathlib import Path
 import re
+import shlex
 import subprocess
 import sys
 import time
@@ -2119,14 +2120,20 @@ def _unmultiplied_rgba8888_to_premultiplied_argb32(rgba8888):
     return argb32
 
 
+def _pformat_subprocess(command):
+    """Pretty-format a subprocess command for printing/logging purposes."""
+    return (command if isinstance(command, str)
+            else " ".join(shlex.quote(os.fspath(arg)) for arg in command))
+
+
 def _check_and_log_subprocess(command, logger, **kwargs):
     """
     Run *command* using `subprocess.check_output`.  If it succeeds, return the
     output (stdout and stderr); if not, raise an exception whose text includes
     the failed command and captured output.  Both the command and the output
     are logged at DEBUG level on *logger*.
     """
-    logger.debug(command)
+    logger.debug('%s', _pformat_subprocess(command))
     try:
         report = subprocess.check_output(
             command, stderr=subprocess.STDOUT, **kwargs)
@@ -2136,7 +2143,7 @@ def _check_and_log_subprocess(command, logger, **kwargs):
             '    {}\n'
             'failed and generated the following output:\n'
             '{}'
-            .format(command, exc.output.decode('utf-8')))
+            .format(_pformat_subprocess(command), exc.output.decode('utf-8')))
     logger.debug(report)
     return report
 
diff --git a/lib/matplotlib/texmanager.py b/lib/matplotlib/texmanager.py
@@ -297,7 +297,7 @@ def make_tex_preview(self, tex, fontsize):
         return texfile
 
     def _run_checked_subprocess(self, command, tex):
-        _log.debug(command)
+        _log.debug(cbook._pformat_subprocess(command))
         try:
             report = subprocess.check_output(command,
                                              cwd=self.texcache,
