Merge pull request #1131 from dmitriy-serdyuk/on-error

Provide exception to `on_error` extensions

blocks/extensions/__init__.py

@@ -72,9 +72,15 @@ def on_resumption(self):
         pass
 
     @callback
-    def on_error(self):
-        """The callback invoked when an error occurs."""
-        pass
+    def on_error(self, exception):
+        """The callback invoked when an error occurs.
+
+        Parameters
+        ----------
+        exception : object
+            Exception occurred during the main loop run.
+
+        """
 
     @callback
     def before_training(self):

blocks/main_loop.py

@@ -189,7 +189,7 @@ def run(self):
                 self.log.current_row['got_exception'] = traceback.format_exc()
                 logger.error("Error occured during training." + error_message)
                 try:
-                    self._run_extensions('on_error')
+                    self._run_extensions('on_error', e)
                 except Exception:
                     logger.error(traceback.format_exc())
                     logger.error("Error occured when running extensions." +

tests/test_main_loop.py

@@ -5,7 +5,7 @@
 from multiprocessing import Process
 
 from fuel.datasets import IterableDataset
-from mock import MagicMock
+from mock import MagicMock, ANY
 from numpy.testing import assert_raises
 from six.moves import cPickle
 
@@ -102,11 +102,11 @@ def test_error():
     ext.on_error = MagicMock()
     main_loop = MockMainLoop(extensions=[ext, FinishAfter(after_epoch=True)])
     assert_raises(KeyError, main_loop.run)
-    ext.on_error.assert_called_once_with()
+    ext.on_error.assert_called_once_with(ANY)
     assert 'got_exception' in main_loop.log.current_row
 
     ext.on_error = MagicMock(side_effect=AttributeError)
     main_loop = MockMainLoop(extensions=[ext, FinishAfter(after_epoch=True)])
     assert_raises(KeyError, main_loop.run)
-    ext.on_error.assert_called_once_with()
+    ext.on_error.assert_called_once_with(ANY)
     assert 'got_exception' in main_loop.log.current_row