More explicit error message when saving to a file with invalid extens…

…ion (#2399) * more explicit error message when saving to a file with invalid extension + test
python-pillow · Feb 17, 2017 · 8fb44a2 · 8fb44a2
1 parent b5f6732
commit 8fb44a2
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Showing 2 changed files with 9 additions and 1 deletion.
diff --git a/PIL/Image.py b/PIL/Image.py
@@ -1715,7 +1715,10 @@ def save(self, fp, format=None, **params):
         if not format:
             if ext not in EXTENSION:
                 init()
-            format = EXTENSION[ext]
+            try:
+                format = EXTENSION[ext]
+            except KeyError:
+                raise ValueError('unknown file extension: {}'.format(ext))
 
         if format.upper() not in SAVE:
             init()

diff --git a/Tests/test_image.py b/Tests/test_image.py
@@ -87,6 +87,11 @@ def test_tempfile(self):
             reloaded = Image.open(fp)
             self.assert_image_similar(im, reloaded, 20)
 
+    def test_unknown_extension(self):
+        im = hopper()
+        temp_file = self.tempfile("temp.unknown")
+        self.assertRaises(ValueError, lambda: im.save(temp_file))
+
     def test_internals(self):
 
         im = Image.new("L", (100, 100))