Add new function

test/test_functions.py

@@ -205,5 +205,41 @@ def test_nonexistent_function(self):
         self.parseEqual(u'%foo{bar}', u'%foo{bar}')
 
 
+class TestFunctionIfDefEmpty(unittest.TestCase):
+
+    def setUp(self):
+        self.values = {
+            'empty_string': u'',
+            'false': False,
+            'non_empty_string': u'test',
+            'none': None,
+        }
+
+    def parseEqual(self, a, b):
+        self.assertEqual(tmep.parse(a, self.values), b)
+
+    # empty_string
+    def test_empty_string(self):
+        self.parseEqual(u'%ifdefempty{empty_string,trueval}', u'trueval')
+
+    # false
+    def test_false(self):
+        self.parseEqual(u'%ifdefempty{false,trueval}', u'trueval')
+
+    # non_empty_string
+    def test_non_empty_string(self):
+        self.parseEqual(u'%ifdefempty{non_empty_string,trueval,falseval}',
+                        u'falseval')
+
+    # none
+    def test_none(self):
+        self.parseEqual(u'%ifdefempty{none,trueval}', u'trueval')
+
+    # nonexistent
+    def test_nonexistent(self):
+        self.parseEqual(u'%ifdefempty{nonexistent,trueval,falseval}',
+                        u'falseval')
+
+
 if __name__ == '__main__':
     unittest.main()

tmep/func.py

@@ -155,6 +155,26 @@ def tmpl_ifdef(self, field, trueval=u'', falseval=u''):
         else:
             return falseval
 
+    def tmpl_ifdefempty(self, field, trueval=u'', falseval=u''):
+        """If field exists and is emtpy return trueval or the field (default)
+        otherwise, emit return falseval (if provided).
+
+        * synopsis: ``%ifdefempty{field,text}`` or \
+            ``%ifdefempty{field,text,falsetext}``
+        * description: If field exists and is empty, then return truetext. \
+            Otherwise, returns falsetext. The field should be \
+            entered without $.
+
+        :param field: The name of the field
+        :param trueval: The string if the condition is true
+        :param falseval: The string if the condition is false
+        :return: The string, based on condition
+        """
+        if field in self.values and not self.values[field]:
+            return trueval
+        else:
+            return falseval
+
     @staticmethod
     def tmpl_left(s, chars):
         """Get the leftmost characters of a string.