Allowing a single string value for "requires" clause

* Making it symmetric to on-success/on-error/on-complete

Change-Id: I902649e7ca5615234fab9638e673ff807e7b8113
(cherry picked from commit c4c0aec7b2)

mistral/tests/unit/engine/test_reverse_workflow.py

@@ -51,6 +51,13 @@ workflows:
         publish:
           result2: <% $.task2 %>
         requires: [task1]
+
+      task3:
+        action: std.noop
+
+      task4:
+        action: std.noop
+        requires: task3
 """
 
 
@@ -127,3 +134,21 @@ class ReverseWorkflowEngineTest(base.EngineTestCase):
         )
 
         self.assertDictEqual({'result2': 'a & b'}, task2_ex.published)
+
+    def test_one_line_requires_syntax(self):
+        wf_input = {'param1': 'a', 'param2': 'b'}
+
+        wf_ex = self.engine.start_workflow(
+            'my_wb.wf1',
+            wf_input,
+            task_name='task4'
+        )
+
+        self._await(lambda: self.is_execution_success(wf_ex.id))
+
+        tasks = db_api.get_task_executions()
+
+        self.assertEqual(2, len(tasks))
+
+        self._assert_single_item(tasks, name='task4', state=states.SUCCESS)
+        self._assert_single_item(tasks, name='task3', state=states.SUCCESS)

mistral/tests/unit/workbook/v2/test_tasks.py

@@ -283,7 +283,8 @@ class TaskSpecValidation(v2_base.WorkflowSpecValidationTestCase):
             ({'requires': None}, True),
             ({'requires': 12345}, True),
             ({'requires': ['echo']}, False),
-            ({'requires': ['echo', 'get']}, False)
+            ({'requires': ['echo', 'get']}, False),
+            ({'requires': 'echo'}, False),
         ]
 
         for require, expect_error in tests:

mistral/tests/unit/workbook/v2/test_workflows.py

@@ -225,6 +225,7 @@ class WorkflowSpecValidation(base.WorkflowSpecValidationTestCase):
             ({'requires': 12345}, True),
             ({'requires': ['echo']}, False),
             ({'requires': ['echo', 'get']}, False),
+            ({'requires': 'echo'}, False),
             ({'retry': {'count': 3, 'delay': 1}}, False),
             ({'retry': {'count': '<% 3 %>', 'delay': 1}}, False),
             ({'retry': {'count': '<% * %>', 'delay': 1}}, True),

mistral/workbook/v2/task_defaults.py

@@ -44,7 +44,9 @@ class TaskDefaultsSpec(base.BaseSpec):
             "on-complete": _on_clause_type,
             "on-success": _on_clause_type,
             "on-error": _on_clause_type,
-            "requires": types.UNIQUE_STRING_LIST
+            "requires": {
+                "oneOf": [types.NONEMPTY_STRING, types.UNIQUE_STRING_LIST]
+            }
         },
         "additionalProperties": False
     }
@@ -97,4 +99,7 @@ class TaskDefaultsSpec(base.BaseSpec):
         return self._on_error
 
     def get_requires(self):
+        if isinstance(self._requires, six.string_types):
+            return [self._requires]
+
         return self._requires

mistral/workbook/v2/tasks.py

@@ -276,7 +276,9 @@ class ReverseWorkflowTaskSpec(TaskSpec):
         "type": "object",
         "properties": {
             "type": {"enum": [_type]},
-            "requires": types.UNIQUE_STRING_LIST
+            "requires": {
+                "oneOf": [types.NONEMPTY_STRING, types.UNIQUE_STRING_LIST]
+            }
         }
     }
 
@@ -289,6 +291,9 @@ class ReverseWorkflowTaskSpec(TaskSpec):
         self._requires = data.get('requires', [])
 
     def get_requires(self):
+        if isinstance(self._requires, six.string_types):
+            return [self._requires]
+
         return self._requires