Do not apply ordinal filtering when a tag appears more than once

Suppose we have the todo item:

    (C) Some item key:value1 key:value2

And then I do an ls:

    topydo ls -x key:value2

Before, this would yield an empty result, which is undesired. Therefore,
only apply ordinal tag filtering when a tag appears exactly once in the
todo item. This is a simple approach, and special operators >, >= etc
will not be applicable:

    topydo ls -x key:>value1

will no longer work. The result could be ambiguous: filter out when none of
the tags match, or only some of them?

test/test_filter.py

@@ -313,12 +313,14 @@ class OrdinalTagFilterTest(TopydoTest):
         self.todo2 = "Bar due:{}".format(self.tomorrow)
         self.todo3 = "Baz due:Nonsense"
         self.todo4 = "Fnord due:2014-10-32"
+        self.todo5 = "Double tags key:value1 key:value2"
 
         self.todos = [
             Todo(self.todo1),
             Todo(self.todo2),
             Todo(self.todo3),
             Todo(self.todo4),
+            Todo(self.todo5),
         ]
 
     def test_filter1(self):
@@ -378,6 +380,18 @@ class OrdinalTagFilterTest(TopydoTest):
         self.assertEqual(len(result), 1)
         self.assertEqual(result[0].source(), self.todo3)
 
+    def test_filter8(self):
+        """
+        OrdinalTagFilter should resort to a simple GrepFilter when a tag
+        appears more than once.
+        """
+        otf = Filter.OrdinalTagFilter('key:value2')
+
+        result = otf.filter(self.todos)
+
+        self.assertEqual(len(result), 1)
+        self.assertEqual(result[0].source(), self.todo5)
+
 
 class CreationFilterTest(TopydoTest):
     def setUp(self):

topydo/lib/Filter.py

@@ -246,9 +246,18 @@ class OrdinalTagFilter(OrdinalFilter):
         As a last resort, it falls back to using a Grep filter to see if the
         user given expression is contained in the todo text.
         """
+        def resort_to_grep_filter():
+            grep = GrepFilter(self.expression)
+            return grep.match(p_todo)
+
         if not self.key or not p_todo.has_tag(self.key):
             return False
 
+        if len(p_todo.tag_values(self.key)) > 1:
+            # we cannot apply an ordening on a tag that appears more than once
+            # in this todo item, therefore use a simple value match
+            return resort_to_grep_filter()
+
         try:
             operand1 = date_string_to_date(p_todo.tag_value(self.key))
             operand2 = relative_date_to_date(self.value)
@@ -264,8 +273,7 @@ class OrdinalTagFilter(OrdinalFilter):
                 operand1 = int(operand1)
                 operand2 = int(operand2)
             except ValueError:
-                grep = GrepFilter(self.expression)
-                return grep.match(p_todo)
+                return resort_to_grep_filter()
 
         return self.compare_operands(operand1, operand2)