Fix: BlobWriter.close() will do nothing if already closed (#887)

* Fix: BlobWriter.close() will do nothing if already closed

* 🦉 Updates from OwlBot post-processor

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Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: andrewsg

google/cloud/storage/fileio.py

@@ -423,9 +423,8 @@ def flush(self):
             )
 
     def close(self):
-        self._checkClosed()  # Raises ValueError if closed.
-
-        self._upload_chunks_from_buffer(1)
+        if not self._buffer.closed:
+            self._upload_chunks_from_buffer(1)
         self._buffer.close()
 
     def _checkClosed(self):

tests/unit/test_fileio.py

@@ -402,6 +402,23 @@ def test_write(self, mock_warn):
             stacklevel=2,
         )
 
+    def test_close_errors(self):
+        blob = mock.Mock(chunk_size=None)
+
+        upload = mock.Mock()
+        transport = mock.Mock()
+
+        blob._initiate_resumable_upload.return_value = (upload, transport)
+
+        writer = self._make_blob_writer(blob)
+
+        writer.close()
+        # Close a second time to verify it successfully does nothing.
+        writer.close()
+        # Try to write to closed file.
+        with self.assertRaises(ValueError):
+            writer.write(TEST_BINARY_DATA)
+
     def test_flush_fails(self):
         blob = mock.Mock(chunk_size=None)
         writer = self._make_blob_writer(blob)