Do not error when thumbnailing invalid files (#8236)

If a file cannot be thumbnailed for some reason (e.g. the file is empty), then
catch the exception and convert it to a reasonable error message for the client.

1 files changed, 29 insertions, 10 deletions

diff --git a/tests/rest/media/v1/test_media_storage.py b/tests/rest/media/v1/test_media_storage.py

index f4f3e56777..5f897d49cf 100644
--- a/tests/rest/media/v1/test_media_storage.py
+++ b/tests/rest/media/v1/test_media_storage.py
@@ -120,12 +120,13 @@ class _TestImage:
     extension = attr.ib(type=bytes)
     expected_cropped = attr.ib(type=Optional[bytes])
     expected_scaled = attr.ib(type=Optional[bytes])
+    expected_found = attr.ib(default=True, type=bool)
 
 
 @parameterized_class(
     ("test_image",),
     [
-        # smol png
+        # smoll png
         (
             _TestImage(
                 unhexlify(
@@ -161,6 +162,8 @@ class _TestImage:
                 None,
             ),
         ),
+        # an empty file
+        (_TestImage(b"", b"image/gif", b".gif", None, None, False,),),
     ],
 )
 class MediaRepoTests(unittest.HomeserverTestCase):
@@ -303,12 +306,16 @@ class MediaRepoTests(unittest.HomeserverTestCase):
         self.assertEqual(headers.getRawHeaders(b"Content-Disposition"), None)
 
     def test_thumbnail_crop(self):
-        self._test_thumbnail("crop", self.test_image.expected_cropped)
+        self._test_thumbnail(
+            "crop", self.test_image.expected_cropped, self.test_image.expected_found
+        )
 
     def test_thumbnail_scale(self):
-        self._test_thumbnail("scale", self.test_image.expected_scaled)
+        self._test_thumbnail(
+            "scale", self.test_image.expected_scaled, self.test_image.expected_found
+        )
 
-    def _test_thumbnail(self, method, expected_body):
+    def _test_thumbnail(self, method, expected_body, expected_found):
         params = "?width=32&height=32&method=" + method
         request, channel = self.make_request(
             "GET", self.media_id + params, shorthand=False
@@ -325,11 +332,23 @@ class MediaRepoTests(unittest.HomeserverTestCase):
         )
         self.pump()
 
-        self.assertEqual(channel.code, 200)
-        if expected_body is not None:
+        if expected_found:
+            self.assertEqual(channel.code, 200)
+            if expected_body is not None:
+                self.assertEqual(
+                    channel.result["body"], expected_body, channel.result["body"]
+                )
+            else:
+                # ensure that the result is at least some valid image
+                Image.open(BytesIO(channel.result["body"]))
+        else:
+            # A 404 with a JSON body.
+            self.assertEqual(channel.code, 404)
             self.assertEqual(
-                channel.result["body"], expected_body, channel.result["body"]
+                channel.json_body,
+                {
+                    "errcode": "M_NOT_FOUND",
+                    "error": "Not found [b'example.com', b'12345?width=32&height=32&method=%s']"
+                    % method,
+                },
             )
-        else:
-            # ensure that the result is at least some valid image
-            Image.open(BytesIO(channel.result["body"]))