Pass flow failures to task's revert method

Now when tasks are reverted, all flows failures seen so far are passed
to revert method as 'flow_failures' keyword argument, as a dictionary
task name => misc.Failure.

Closes-bug: #1246616
Change-Id: I81f8c10684d54aaf5c31bb3badb6afe4c949f680

taskflow/engines/action_engine/task_action.py

@@ -112,6 +112,7 @@ class TaskAction(base.Action):
                        engine=engine):
             kwargs = engine.storage.fetch_mapped_args(self._task.rebind)
             kwargs['result'] = engine.storage.get(self._id)
+            kwargs['flow_failures'] = engine.storage.get_failures()
             try:
                 self._task.revert(**kwargs)
             except Exception:

taskflow/tests/unit/test_action_engine.py

@@ -30,8 +30,10 @@ import taskflow.engines
 from taskflow.engines.action_engine import engine as eng
 from taskflow.persistence import logbook
 from taskflow import states
+from taskflow import task
 from taskflow import test
 from taskflow.tests import utils
+from taskflow.utils import misc
 from taskflow.utils import persistence_utils as p_utils
 
 
@@ -186,6 +188,26 @@ class EngineLinearFlowTest(utils.EngineTestBase):
              'fail reverted(Failure: RuntimeError: Woot!)',
              'task2 reverted(5)', 'task1 reverted(5)'])
 
+    def test_flow_failures_are_passed_to_revert(self):
+        class CheckingTask(task.Task):
+            def execute(m_self):
+                return 'RESULT'
+
+            def revert(m_self, result, flow_failures):
+                self.assertEqual(result, 'RESULT')
+                self.assertEqual(flow_failures.keys(), ['fail1'])
+                fail = flow_failures['fail1']
+                self.assertIsInstance(fail, misc.Failure)
+                self.assertEqual(str(fail), 'Failure: RuntimeError: Woot!')
+
+        flow = lf.Flow('test').add(
+            CheckingTask(),
+            utils.FailingTask(self.values, 'fail1')
+        )
+        engine = self._make_engine(flow)
+        with self.assertRaisesRegexp(RuntimeError, '^Woot'):
+            engine.run()
+
 
 class EngineParallelFlowTest(utils.EngineTestBase):
 

taskflow/tests/unit/test_suspend_flow.py

@@ -75,7 +75,7 @@ class AutoSuspendingTask(TestTask):
         engine.suspend()
         return result
 
-    def revert(self, engine, result):
+    def revert(self, engine, result, flow_failures):
         super(AutoSuspendingTask, self).revert(**{'result': result})
 
 
@@ -84,7 +84,7 @@ class AutoSuspendingTaskOnRevert(TestTask):
     def execute(self, engine):
         return super(AutoSuspendingTaskOnRevert, self).execute()
 
-    def revert(self, engine, result):
+    def revert(self, engine, result, flow_failures):
         super(AutoSuspendingTaskOnRevert, self).revert(**{'result': result})
         engine.suspend()