Adding length() YAQL function

* Switched YAQL to version 0.2.3
* Refactored expressions to use custome YAQL contexts
  with additional functions
* Added unit tests

Change-Id: I12f4d56308a011a3a588028df20becb519e2e684

mistral/expressions.py

@@ -21,6 +21,7 @@ import six
 import yaql
 
 from mistral.openstack.common import log as logging
+from mistral import yaql_utils
 
 LOG = logging.getLogger(__name__)
 
@@ -56,11 +57,14 @@ class Evaluator(object):
 
 class YAQLEvaluator(Evaluator):
     @classmethod
-    def evaluate(cls, expression, context):
+    def evaluate(cls, expression, data_context):
         LOG.debug("Evaluating YAQL expression [expression='%s', context=%s]"
-                  % (expression, context))
+                  % (expression, data_context))
 
-        return yaql.parse(expression).evaluate(context)
+        return yaql.parse(expression).evaluate(
+            data=data_context,
+            context=yaql_utils.create_yaql_context()
+        )
 
     @classmethod
     def is_expression(cls, s):
@@ -74,10 +78,10 @@ class InlineYAQLEvaluator(YAQLEvaluator):
     find_expression_pattern = re.compile("\{\$\.*[^\}]*\}")
 
     @classmethod
-    def evaluate(cls, expression, context):
+    def evaluate(cls, expression, data_context):
         if super(InlineYAQLEvaluator, cls).is_expression(expression):
             return super(InlineYAQLEvaluator,
-                         cls).evaluate(expression, context)
+                         cls).evaluate(expression, data_context)
 
         result = expression
         found_expressions = cls.find_inline_expressions(expression)
@@ -86,7 +90,7 @@ class InlineYAQLEvaluator(YAQLEvaluator):
             for expr in found_expressions:
                 trim_expr = expr.strip("{}")
                 evaluated = super(InlineYAQLEvaluator,
-                                  cls).evaluate(trim_expr, context)
+                                  cls).evaluate(trim_expr, data_context)
 
                 replacement = str(evaluated) if evaluated else expr
                 result = result.replace(expr, replacement)

mistral/tests/unit/test_expressions.py

@@ -138,3 +138,11 @@ class YaqlEvaluatorTest(base.BaseTest):
             },
             applied
         )
+
+    def test_function_length(self):
+        self.assertEqual(3, expr.evaluate('$.length()', [1, 2, 3]))
+        self.assertEqual(2, expr.evaluate('$.length()', ['one', 'two']))
+        self.assertEqual(4, expr.evaluate(
+            '$.array.length()',
+            {'array': ['1', '2', '3', '4']})
+        )

mistral/yaql_utils.py

@@ -0,0 +1,37 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2014 - 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 create_yaql_context():
+
+    ctx = yaql.create_context()
+
+    _register_functions(ctx)
+
+    return ctx
+
+
+def _register_functions(yaql_ctx):
+    yaql_ctx.register_function(length, 'length')
+    yaql_ctx.register_function(length, 'size')
+
+
+# Additional convenience YAQL functions.
+
+def length(a):
+    return len(a())

requirements.txt

@@ -24,7 +24,7 @@ networkx>=1.8
 six>=1.7.0
 SQLAlchemy>=0.8.4,<=0.8.99,>=0.9.7,<=0.9.99
 stevedore>=1.0.0  # Apache-2.0
-yaql==0.2.1 # This is not in global requirements
+yaql==0.2.3 # This is not in global requirements
 jsonschema>=2.0.0,<3.0.0
 mock>=1.0
 keystonemiddleware>=1.0.0