Bugfix the error in DataEntity.validate_datatype with functions

Change-Id: I42a369cccfb890ccdb8d49e01a220752cd710b4d
Related-Bug: 1583022

toscaparser/dataentity.py

@@ -122,6 +122,9 @@ class DataEntity(object):
         If type is list or map, validate its entry by entry_schema(if defined)
         If type is a user-defined complex datatype, custom_def is required.
         '''
+        from toscaparser.functions import is_function
+        if is_function(value):
+            return value
         if type == Schema.STRING:
             return validateutils.validate_string(value)
         elif type == Schema.INTEGER:

toscaparser/tests/test_datatypes.py

@@ -504,3 +504,14 @@ class DataTypeTest(TestCase):
                         'value of type "tosca.datatypes.Credential" contains'
                         ' unknown field "some_field". Refer to the definition'
                         ' to verify valid values'), err.__str__())
+
+    def test_functions_datatype(self):
+        value_snippet = '''
+        admin_credential:
+          user: username
+          token: { get_input: password }
+        '''
+        value = yamlparser.simple_parse(value_snippet)
+        data = DataEntity('tosca.datatypes.Credential',
+                          value.get('admin_credential'))
+        self.assertIsNotNone(data.validate())