Fix mimetype determination for empty files (#3661)

Closes #3658
comic · Oct 28, 2024 · cda0704 · cda0704
1 parent 792b809
commit cda0704
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Showing 2 changed files with 17 additions and 6 deletions.
diff --git a/app/grandchallenge/uploads/models.py b/app/grandchallenge/uploads/models.py
@@ -201,12 +201,22 @@ def assign_permissions(self):
     def mimetype_from_file(self):
         if self.status != self.StatusChoices.COMPLETED:
             raise RuntimeError("Cannot get mimetype of incomplete upload")
-        header = self._client.get_object(
-            Bucket=self.bucket,
-            Key=self.key,
-            # 2048 bytes for best results with libmagic
-            Range="bytes=0-2047",
-        )["Body"].read()
+
+        response = self._client.head_object(Bucket=self.bucket, Key=self.key)
+        object_size = int(response["ContentLength"])
+
+        # 2048 bytes for best results with libmagic
+        max_bytes = min(2047, object_size)
+
+        if max_bytes == 0:
+            return "application/x-empty"
+        else:
+            header = self._client.get_object(
+                Bucket=self.bucket,
+                Key=self.key,
+                Range=f"bytes=0-{max_bytes}",
+            )["Body"].read()
+
         return magic.from_buffer(header, mime=True)
 
     def create_multipart_upload(self):

diff --git a/app/tests/uploads_tests/test_models.py b/app/tests/uploads_tests/test_models.py
@@ -365,6 +365,7 @@ def test_can_upload_more_other_objects(settings):
 @pytest.mark.parametrize(
     "content,expected_mimetype",
     (
+        (b"", "application/x-empty"),
         (b"hello", "text/plain"),
         (
             b"\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x00\x01\x00\x00\x00\x01\x08\x00\x00\x00\x00:~\x9bU\x00\x00\x00\nIDATx\x9cc`\x00\x00\x00\x02\x00\x01H\xaf\xa4q\x00\x00\x00\x00IEND\xaeB`\x82",