[gcloud] Fix double decompression when using gzip (#1457)

storages/backends/gcloud.py

@@ -62,10 +62,9 @@ def _get_file(self):
             )
             if "r" in self._mode:
                 self._is_dirty = False
+                # This automatically decompresses the file
                 self.blob.download_to_file(self._file, checksum="crc32c")
                 self._file.seek(0)
-            if self._storage.gzip and self.blob.content_encoding == "gzip":
-                self._file = self._decompress_file(mode=self._mode, file=self._file)
         return self._file
 
     def _set_file(self, value):

tests/test_gcloud.py

@@ -14,6 +14,7 @@
 from google.cloud.storage.retry import DEFAULT_RETRY
 
 from storages.backends import gcloud
+from storages.backends.gcloud import GoogleCloudFile
 
 
 class GCloudTestCase(TestCase):
@@ -571,3 +572,17 @@ def test_storage_save_gzip(self, *args):
             self.assertEqual(zfile.read(), b"I should be gzip'd")
         finally:
             patcher.stop()
+
+    def test_storage_read_gzip(self, *args):
+        """
+        Test reading a gzipped file decompresses content only once.
+        """
+        name = "test_storage_save.css"
+        file = GoogleCloudFile(name, "rb", self.storage)
+        blob = mock.MagicMock()
+        file.blob = blob
+        blob.download_to_file = lambda f, checksum=None: f.write(b"No gzip")
+        blob.content_encoding = "gzip"
+        f = file._get_file()
+
+        f.read()  # This should not fail