Fix the error with CAA where no image would be downloaded when thumbnails are missing

beetsplug/fetchart.py

@@ -399,10 +399,15 @@ class CoverArtArchive(RemoteArtSource):
                     if 'Front' not in item['types']:
                         continue
 
-                    if preferred_width:
-                        yield item['thumbnails'][preferred_width]
-                    else:
-                        yield item['image']
+                    # If there is a pre-sized thumbnail of the desired size
+                    # we select it. Otherwise, we return the raw image.
+                    image_url: str = item["image"]
+                    if preferred_width is not None:
+                        if isinstance(item.get("thumbnails"), dict):
+                            image_url = item["thumbnails"].get(
+                                preferred_width, image_url
+                            )
+                    yield image_url
                 except KeyError:
                     pass
 

docs/changelog.rst

@@ -128,6 +128,9 @@ New features:
 * :doc:`/plugins/fetchart`: Fix the error with CoverArtArchive where the
   `maxwidth` option would not be used to download a pre-sized thumbnail for
   release groups, as is already done with releases.
+* :doc:`/plugins/fetchart`: Fix the error with CoverArtArchive where no cover
+  would be found when the `maxwidth` option matches a pre-sized thumbnail size,
+  but no thumbnail is provided by CAA. We now fallback to the raw image.
 
 Bug fixes:
 

test/test_art.py

@@ -130,6 +130,39 @@ class CAAHelper():
       }
     ],
     "release": "https://musicbrainz.org/release/releaseid"
+}"""
+    RESPONSE_RELEASE_WITHOUT_THUMBNAILS = """{
+    "images": [
+      {
+        "approved": false,
+        "back": false,
+        "comment": "GIF",
+        "edit": 12345,
+        "front": true,
+        "id": 12345,
+        "image": "http://coverartarchive.org/release/rid/12345.gif",
+        "types": [
+          "Front"
+        ]
+      },
+      {
+        "approved": false,
+        "back": false,
+        "comment": "",
+        "edit": 12345,
+        "front": false,
+        "id": 12345,
+        "image": "http://coverartarchive.org/release/rid/12345.jpg",
+        "thumbnails": {
+            "large": "http://coverartarchive.org/release/rgid/12345-500.jpg",
+            "small": "http://coverartarchive.org/release/rgid/12345-250.jpg"
+        },
+        "types": [
+          "Front"
+        ]
+      }
+    ],
+    "release": "https://musicbrainz.org/release/releaseid"
 }"""
     RESPONSE_GROUP = """{
         "images": [
@@ -155,6 +188,23 @@ class CAAHelper():
         ],
         "release": "https://musicbrainz.org/release/release-id"
     }"""
+    RESPONSE_GROUP_WITHOUT_THUMBNAILS = """{
+        "images": [
+          {
+            "approved": false,
+            "back": false,
+            "comment": "",
+            "edit": 12345,
+            "front": true,
+            "id": 12345,
+            "image": "http://coverartarchive.org/release/releaseid/12345.jpg",
+            "types": [
+              "Front"
+            ]
+          }
+        ],
+        "release": "https://musicbrainz.org/release/release-id"
+    }"""
 
     def mock_caa_response(self, url, json):
         responses.add(responses.GET, url, body=json,
@@ -537,6 +587,26 @@ class CoverArtArchiveTest(UseThePlugin, CAAHelper):
         for candidate in candidates:
             self.assertTrue(f"-{maxwidth}.jpg" in candidate.url)
 
+    def test_caa_finds_image_if_maxwidth_is_set_and_thumbnails_is_empty(self):
+        # CAA provides pre-sized thumbnails of width 250px, 500px, and 1200px
+        # We only test with one of them here
+        maxwidth = 1200
+        self.settings = Settings(maxwidth=maxwidth)
+
+        album = _common.Bag(
+            mb_albumid=self.MBID_RELASE, mb_releasegroupid=self.MBID_GROUP
+        )
+        self.mock_caa_response(
+            self.RELEASE_URL, self.RESPONSE_RELEASE_WITHOUT_THUMBNAILS
+        )
+        self.mock_caa_response(
+            self.GROUP_URL, self.RESPONSE_GROUP_WITHOUT_THUMBNAILS,
+        )
+        candidates = list(self.source.get(album, self.settings, []))
+        self.assertEqual(len(candidates), 3)
+        for candidate in candidates:
+            self.assertFalse(f"-{maxwidth}.jpg" in candidate.url)
+
 
 class FanartTVTest(UseThePlugin):
     RESPONSE_MULTIPLE = """{