Storage: no longer enforce 'destination.content_type' in 'Blob.compose'.

storage/google/cloud/storage/blob.py

@@ -1374,13 +1374,7 @@ def compose(self, sources, client=None):
                       ``NoneType``
         :param client: Optional. The client to use.  If not passed, falls back
                        to the ``client`` stored on the blob's bucket.
-
-        :raises: :exc:`ValueError` if this blob does not have its
-                 :attr:`content_type` set.
         """
-        if self.content_type is None:
-            raise ValueError("Destination 'content_type' not set.")
-
         client = self._require_client(client)
         query_params = {}
 

storage/tests/system.py

@@ -779,6 +779,26 @@ def test_compose_create_new_blob(self):
         composed = destination.download_as_string()
         self.assertEqual(composed, SOURCE_1 + SOURCE_2)
 
+    def test_compose_create_new_blob_wo_content_type(self):
+        SOURCE_1 = b'AAA\n'
+        source_1 = self.bucket.blob('source-1')
+        source_1.upload_from_string(SOURCE_1)
+        self.case_blobs_to_delete.append(source_1)
+
+        SOURCE_2 = b'BBB\n'
+        source_2 = self.bucket.blob('source-2')
+        source_2.upload_from_string(SOURCE_2)
+        self.case_blobs_to_delete.append(source_2)
+
+        destination = self.bucket.blob('destination')
+
+        destination.compose([source_1, source_2])
+        self.case_blobs_to_delete.append(destination)
+
+        self.assertIsNone(destination.content_type)
+        composed = destination.download_as_string()
+        self.assertEqual(composed, SOURCE_1 + SOURCE_2)
+
     def test_compose_replace_existing_blob(self):
         BEFORE = b'AAA\n'
         original = self.bucket.blob('original')

storage/tests/unit/test_blob.py

@@ -2113,15 +2113,35 @@ def test_compose_wo_content_type_set(self):
         SOURCE_1 = 'source-1'
         SOURCE_2 = 'source-2'
         DESTINATION = 'destinaton'
-        connection = _Connection()
+        RESOURCE = {}
+        after = ({'status': http_client.OK}, RESOURCE)
+        connection = _Connection(after)
         client = _Client(connection)
         bucket = _Bucket(client=client)
         source_1 = self._make_one(SOURCE_1, bucket=bucket)
         source_2 = self._make_one(SOURCE_2, bucket=bucket)
         destination = self._make_one(DESTINATION, bucket=bucket)
+        # no destination.content_type set
 
-        with self.assertRaises(ValueError):
-            destination.compose(sources=[source_1, source_2])
+        destination.compose(sources=[source_1, source_2])
+
+        self.assertIsNone(destination.content_type)
+
+        kw = connection._requested
+        self.assertEqual(len(kw), 1)
+        self.assertEqual(kw[0], {
+            'method': 'POST',
+            'path': '/b/name/o/%s/compose' % DESTINATION,
+            'query_params': {},
+            'data': {
+                'sourceObjects': [
+                    {'name': source_1.name},
+                    {'name': source_2.name},
+                ],
+                'destination': {},
+            },
+            '_target_object': destination,
+        })
 
     def test_compose_minimal_w_user_project(self):
         SOURCE_1 = 'source-1'