Ensure activity and decision tasks cannot progress on a closed workflow

This is a second barrier because I'm a little nervous about this and I
don't want moto/swf to make any activity progress while in the real
world service, it's strictly impossible once the execution is closed.
Python doesn't seem to have any nice way of freezing an object so here
we go with a manual boundary...

moto/swf/exceptions.py

@@ -119,3 +119,8 @@ class SWFDecisionValidationException(SWFClientError):
             prefix.format(count) + "; ".join(messages),
             "com.amazon.coral.validate#ValidationException"
         )
+
+
+class SWFWorkflowExecutionClosedError(Exception):
+    def __str__(self):
+        return repr("Cannot change this object because the WorkflowExecution is closed")

moto/swf/models/activity_task.py

@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 from datetime import datetime
 import uuid
 
+from ..exceptions import SWFWorkflowExecutionClosedError
 from ..utils import now_timestamp
 
 
@@ -24,6 +25,10 @@ class ActivityTask(object):
         # but that shouldn't be a problem for tests
         self.scheduled_at = datetime.now()
 
+    def _check_workflow_execution_open(self):
+        if not self.workflow_execution.open:
+            raise SWFWorkflowExecutionClosedError()
+
     @property
     def open(self):
         return self.state in ["SCHEDULED", "STARTED"]
@@ -45,9 +50,11 @@ class ActivityTask(object):
         self.started_event_id = started_event_id
 
     def complete(self):
+        self._check_workflow_execution_open()
         self.state = "COMPLETED"
 
     def fail(self):
+        self._check_workflow_execution_open()
         self.state = "FAILED"
 
     def reset_heartbeat_clock(self):
@@ -63,5 +70,9 @@ class ActivityTask(object):
 
     def process_timeouts(self):
         if self.has_timedout():
+            self.timeout()
+
+    def timeout(self):
+        self._check_workflow_execution_open()
         self.state = "TIMED_OUT"
         self.timeout_type = "HEARTBEAT"

moto/swf/models/decision_task.py

@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 from datetime import datetime
 import uuid
 
+from ..exceptions import SWFWorkflowExecutionClosedError
 from ..utils import now_timestamp
 
 
@@ -21,6 +22,10 @@ class DecisionTask(object):
         self.scheduled_at = datetime.now()
         self.timeout_type = None
 
+    def _check_workflow_execution_open(self):
+        if not self.workflow_execution.open:
+            raise SWFWorkflowExecutionClosedError()
+
     def to_full_dict(self, reverse_order=False):
         events = self.workflow_execution.events(reverse_order=reverse_order)
         hsh = {
@@ -42,6 +47,7 @@ class DecisionTask(object):
         self.started_event_id = started_event_id
 
     def complete(self):
+        self._check_workflow_execution_open()
         self.state = "COMPLETED"
 
     def has_timedout(self):
@@ -54,5 +60,9 @@ class DecisionTask(object):
 
     def process_timeouts(self):
         if self.has_timedout():
+            self.timeout()
+
+    def timeout(self):
+        self._check_workflow_execution_open()
         self.state = "TIMED_OUT"
         self.timeout_type = "START_TO_CLOSE"

tests/test_swf/models/test_activity_task.py

@@ -1,6 +1,7 @@
 from freezegun import freeze_time
 from sure import expect
 
+from moto.swf.exceptions import SWFWorkflowExecutionClosedError
 from moto.swf.models import (
     ActivityTask,
     ActivityType,
@@ -123,3 +124,21 @@ def test_activity_task_cannot_timeout_on_closed_workflow_execution():
         wfe.has_timedout().should.equal(True)
         wfe.process_timeouts()
         task.has_timedout().should.equal(False)
+
+def test_activity_task_cannot_change_state_on_closed_workflow_execution():
+    wfe = make_workflow_execution()
+    wfe.start()
+
+    task = ActivityTask(
+        activity_id="my-activity-123",
+        activity_type="foo",
+        input="optional",
+        scheduled_event_id=117,
+        timeouts=ACTIVITY_TASK_TIMEOUTS,
+        workflow_execution=wfe,
+    )
+    wfe.complete(123)
+
+    task.timeout.when.called_with().should.throw(SWFWorkflowExecutionClosedError)
+    task.complete.when.called_with().should.throw(SWFWorkflowExecutionClosedError)
+    task.fail.when.called_with().should.throw(SWFWorkflowExecutionClosedError)

tests/test_swf/models/test_decision_task.py

@@ -1,6 +1,7 @@
 from freezegun import freeze_time
 from sure import expect
 
+from moto.swf.exceptions import SWFWorkflowExecutionClosedError
 from moto.swf.models import DecisionTask
 
 from ..utils import make_workflow_execution
@@ -61,3 +62,13 @@ def test_decision_task_cannot_timeout_on_closed_workflow_execution():
         wfe.has_timedout().should.equal(True)
         wfe.process_timeouts()
         dt.has_timedout().should.equal(False)
+
+def test_decision_task_cannot_change_state_on_closed_workflow_execution():
+    wfe = make_workflow_execution()
+    wfe.start()
+    task = DecisionTask(wfe, 123)
+
+    wfe.complete(123)
+
+    task.timeout.when.called_with().should.throw(SWFWorkflowExecutionClosedError)
+    task.complete.when.called_with().should.throw(SWFWorkflowExecutionClosedError)