Working on Data Flow (step 2)

* Added ExpressionEvaluator interface and YAQL implementation
* Removed yaql_utils, evaluator is now a more flexible replacement
* Fixed the places where yaql_utils was used
* Adjusted test cases

Change-Id: I7de70e678c211df34788763047b8361de0d3902a

mistral/engine/actions/action_factory.py

@@ -64,7 +64,7 @@ def get_rest_action(task):
 
     # input_yaql = task.get('input')
     # TODO(nmakhotkin) extract input from context within the YAQL expression
-    task_input = {}  # yaql_utils.evaluate(input_yaql, ctx)
+    task_input = {}  # expressions.evaluate(input_expr, ctx)
     task_data = {}
 
     if method.upper() == "GET":

mistral/engine/actions/action_helper.py

@@ -17,7 +17,7 @@
 from mistral.engine.actions import action_types as a_t
 from mistral import exceptions as exc
 from mistral.engine import states
-from mistral.utils import yaql_utils
+from mistral.engine import expressions as expr
 
 
 def get_action_type(task):
@@ -30,16 +30,17 @@ def is_task_synchronous(task):
 
 def extract_state_result(action, action_result):
     # All non-Mistral tasks are sync-auto because service doesn't know
-    # about Mistral and we need to receive the result immediately
+    # about Mistral and we need to receive the result immediately.
     if action.type != a_t.MISTRAL_REST_API:
         if action.result_helper.get('select'):
-            result = yaql_utils.evaluate(action.result_helper['select'],
+            result = expr.evaluate(action.result_helper['select'],
                                    action_result)
             # TODO(nmakhotkin) get state for other actions
             state = states.get_state_by_http_status_code(action.status)
         else:
             raise exc.InvalidActionException("Cannot get the result of sync "
                                              "task without YAQL expression")
+
         return state, result
     raise exc.InvalidActionException("Error. Wrong type of action to "
                                      "retrieve the result")

mistral/engine/expressions.py

@@ -0,0 +1,57 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2013 - Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+
+import abc
+import yaql
+
+from mistral.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
+
+
+class Evaluator(object):
+    """Expression evaluator interface.
+
+    Having this interface gives the flexibility to change the actual expression
+    language used in Mistral DSL for conditions, output calculation etc.
+    """
+
+    @classmethod
+    @abc.abstractmethod
+    def evaluate(cls, expression, context):
+        """Evaluates the expression against the given data context.
+
+        :param expression: Expression string
+        :param context: Data context
+        :return: Expression result
+        """
+        pass
+
+
+class YAQLEvaluator(Evaluator):
+    @classmethod
+    def evaluate(cls, expression, context):
+        LOG.debug("Evaluating YAQL expression [expression='%s', context=%s]")
+
+        return yaql.parse(expression).evaluate(context)
+
+
+# TODO(rakhmerov): Make it configurable.
+_EVALUATOR = YAQLEvaluator()
+
+
+def evaluate(expression, context):
+    _EVALUATOR.evaluate(expression, context)

mistral/tests/unit/test_expressions.py

@@ -16,7 +16,7 @@
 
 import unittest2
 
-from mistral.utils import yaql_utils
+from mistral.engine import expressions as expr
 
 
 DATA = {
@@ -44,33 +44,37 @@ SERVERS = {
 }
 
 
-class YaqlTest(unittest2.TestCase):
+class YaqlEvaluatorTest(unittest2.TestCase):
+    def setUp(self):
+        super(YaqlEvaluatorTest, self).setUp()
+        self._evaluator = expr.YAQLEvaluator()
+
     def test_expression_result(self):
-        res = yaql_utils.evaluate("$.server", DATA)
+        res = self._evaluator.evaluate('$.server', DATA)
         self.assertEqual(res, {
-            "id": "03ea824a-aa24-4105-9131-66c48ae54acf",
-            "name": "cloud-fedora",
-            "status": "ACTIVE"
+            'id': "03ea824a-aa24-4105-9131-66c48ae54acf",
+            'name': 'cloud-fedora',
+            'status': 'ACTIVE'
         })
 
-        res = yaql_utils.evaluate("$.server.id", DATA)
-        self.assertEqual(res, "03ea824a-aa24-4105-9131-66c48ae54acf")
+        res = self._evaluator.evaluate('$.server.id', DATA)
+        self.assertEqual(res, '03ea824a-aa24-4105-9131-66c48ae54acf')
 
-        res = yaql_utils.evaluate("$.server.status = 'ACTIVE'", DATA)
+        res = self._evaluator.evaluate("$.server.status = 'ACTIVE'", DATA)
         self.assertTrue(res)
 
     def test_wrong_expression(self):
-        res = yaql_utils.evaluate("$.status = 'Invalid value'", DATA)
+        res = self._evaluator.evaluate("$.status = 'Invalid value'", DATA)
         self.assertFalse(res)
 
-        res = yaql_utils.evaluate("$.wrong_key", DATA)
+        res = self._evaluator.evaluate('$.wrong_key', DATA)
         self.assertIsNone(res)
 
-        expression_str = "invalid_expression_string"
-        res = yaql_utils.evaluate(expression_str, DATA)
+        expression_str = 'invalid_expression_string'
+        res = self._evaluator.evaluate(expression_str, DATA)
         self.assertEqual(res, expression_str)
 
     def test_select_result(self):
-        res = yaql_utils.evaluate("$.servers[$.name = ubuntu]", SERVERS)
+        res = self._evaluator.evaluate('$.servers[$.name = ubuntu]', SERVERS)
         item = list(res)[0]
         self.assertEqual(item, {'name': 'ubuntu'})

mistral/utils/yaql_utils.py

@@ -1,21 +0,0 @@
-# -*- coding: utf-8 -*-
-#
-# Copyright 2013 - Mirantis, Inc.
-#
-#    Licensed under the Apache License, Version 2.0 (the "License");
-#    you may not use this file except in compliance with the License.
-#    You may obtain a copy of the License at
-#
-#        http://www.apache.org/licenses/LICENSE-2.0
-#
-#    Unless required by applicable law or agreed to in writing, software
-#    distributed under the License is distributed on an "AS IS" BASIS,
-#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-#    See the License for the specific language governing permissions and
-#    limitations under the License.
-
-import yaql
-
-
-def evaluate(expression_str, data):
-    return yaql.parse(expression_str).evaluate(data)