added defined/undefined tests

lib/ansible/plugins/test/core.py

@@ -84,6 +84,15 @@ def search(value, pattern='', ignorecase=False, multiline=False):
     ''' Perform a `re.search` returning a boolean '''
     return regex(value, pattern, ignorecase, multiline, 'search')
 
+def undefined(a):
+    ''' Test if a variable is undefined '''
+    from jinja2.runtime import Undefined
+    return isinstance(a, Undefined)
+
+def defined(a):
+    ''' Test if a variable is defined '''
+    return not undefined(a)
+
 class TestModule(object):
     ''' Ansible core jinja2 tests '''
 
@@ -107,4 +116,8 @@ class TestModule(object):
             'match': match,
             'search': search,
             'regex': regex,
+
+            # variable testing
+            'undefined': undefined,
+            'defined': defined,
         }