Add __slots__ to Tags.

pekkaklarck · pekkaklarck · commit d0f7699e45ca · 2021-10-07T16:13:08.000+03:00
This reduces memory usage a bit per each Tags instance. Because each TestCase and more importantly Keyword object has tags, that adds up. This is part of memory reduction explained in #4114.
diff --git a/src/robot/model/tags.py b/src/robot/model/tags.py
@@ -13,37 +13,34 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-from robot.utils import (Matcher, normalize, NormalizedDict, is_string, py3to2,
-                         setter, unic, unicode)
+from robot.utils import (is_string, normalize, NormalizedDict, Matcher, py3to2,
+                         unic, unicode)
 
 
 @py3to2
 class Tags(object):
+    __slots__ = ['_tags']
 
     def __init__(self, tags=None):
-        self._tags = tags
-
-    @setter
-    def _tags(self, tags):
         if not tags:
-            return ()
-        if is_string(tags):
+            tags = ()
+        elif is_string(tags):
             tags = (tags,)
-        return self._deduplicate_normalized(tags)
+        self._tags = self._normalize(tags)
 
-    def _deduplicate_normalized(self, tags):
+    def _normalize(self, tags):
         normalized = NormalizedDict(((unic(t), 1) for t in tags), ignore='_')
         for removed in '', 'NONE':
             if removed in normalized:
                 normalized.pop(removed)
         return tuple(normalized)
 
     def add(self, tags):
-        self._tags = tuple(self) + tuple(Tags(tags))
+        self._tags = self._normalize(tuple(self) + tuple(Tags(tags)))
 
     def remove(self, tags):
         tags = TagPatterns(tags)
-        self._tags = [t for t in self if not tags.match(t)]
+        self._tags = tuple([t for t in self if not tags.match(t)])
 
     def match(self, tags):
         return TagPatterns(tags).match(self)
diff --git a/utest/model/test_tags.py b/utest/model/test_tags.py
@@ -1,6 +1,7 @@
 import unittest
 
-from robot.utils.asserts import assert_equal, assert_false, assert_not_equal, assert_true
+from robot.utils.asserts import (assert_equal, assert_false, assert_not_equal,
+                                 assert_raises, assert_true)
 from robot.utils import seq2str, IRONPYTHON, PY2, unicode
 from robot.model.tags import Tags, TagPattern, TagPatterns
 
@@ -156,6 +157,10 @@ def test__eq__normalized(self):
         assert_equal(Tags(['Hello world', 'Foo', 'Not_world']),
                      Tags(['nOT WORLD', 'FOO', 'hello world']))
 
+    def test__slots__(self):
+        assert_raises(AttributeError, setattr, Tags(), 'attribute', 'value')
+
+
 class TestNormalizing(unittest.TestCase):
 
     def test_empty(self):
