Backport PR #10754: Fix image fmt detection for Path input.

jklymak · MeeseeksDev[bot] · commit 76f0285386bb · 2018-03-12T19:42:25.000Z
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -2159,6 +2159,8 @@ def print_figure(self, filename, dpi=None, facecolor=None, edgecolor=None,
 
         if format is None:
             # get format from filename, or from backend's default filetype
+            if isinstance(filename, getattr(os, "PathLike", ())):
+                filename = os.fspath(filename)
             if isinstance(filename, six.string_types):
                 format = os.path.splitext(filename)[1][1:]
             if format is None or format == '':
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -1,6 +1,5 @@
 from __future__ import absolute_import, division, print_function
 
-import os
 import sys
 import warnings
 
@@ -379,6 +378,11 @@ def test_figure_repr():
 
 @pytest.mark.skipif(sys.version_info < (3, 6), reason="requires Python 3.6+")
 @pytest.mark.parametrize("fmt", ["png", "pdf", "ps", "eps", "svg"])
-def test_fspath(fmt):
+def test_fspath(fmt, tmpdir):
     from pathlib import Path
-    plt.savefig(Path(os.devnull), format=fmt)
+    out = Path(tmpdir, "test.{}".format(fmt))
+    plt.savefig(out)
+    with out.open("rb") as file:
+        # All the supported formats include the format name (case-insensitive)
+        # in the first 100 bytes.
+        assert fmt.encode("ascii") in file.read(100).lower()
