Allow None for 'params' when starting a workflow execution

Change-Id: Ic28352d9acbe9e3f53a9d33a4ff0a5f99261f53f
Closes-Bug: #1793651

mistral/api/controllers/v2/execution.py

@@ -274,7 +274,7 @@ class ExecutionsController(rest.RestController):
             result_exec_dict.get('id'),
             result_exec_dict.get('input'),
             description=result_exec_dict.get('description', ''),
-            **result_exec_dict.get('params', {})
+            **result_exec_dict.get('params') or {}
         )
 
         return resources.Execution.from_dict(result)

mistral/tests/unit/api/v2/test_executions.py

@@ -683,6 +683,23 @@ class TestExecutionsController(base.APITest):
             **json.loads(exec_dict['params'])
         )
 
+    @mock.patch.object(rpc_clients.EngineClient, 'start_workflow')
+    def test_post_with_params_none(self, start_wf_func):
+        wf_ex_dict = WF_EX.to_dict()
+
+        start_wf_func.return_value = wf_ex_dict
+
+        json_body = WF_EX_JSON_WITH_DESC.copy()
+
+        json_body['params'] = None
+
+        expected_json = WF_EX_JSON_WITH_DESC
+
+        resp = self.app.post_json('/v2/executions', json_body)
+
+        self.assertEqual(201, resp.status_int)
+        self.assertDictEqual(expected_json, resp.json)
+
     @mock.patch.object(
         rpc_clients.EngineClient,
         'start_workflow',

releasenotes/notes/allow_none_for_workflow_execution_params-f25b752e207d51d7.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixed a backward compatibility issue: there was a change made in Rocky
+    that disallowed the 'params' property of a workflow execution to be None
+    when one wants to start a workflow.