No longer flag constant list, tuple and dict

Author: tonybaloney

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Renamed the global usage in loop to `loop-global-usage`
 * Added support for invariant f-strings
+* Bugfix: Doesn't highlight list, tuple or dict with only constant values as being invariant
 
 ## 0.7.1 (1st April 2022)
 

perflint/for_loop_checker.py

@@ -193,6 +193,27 @@ def visit_while(self, node: nodes.While) -> None:
         self._loop_assignments.append(set())
         self._ignore.append(node.test)
 
+    def _visit_sequence(self, node: Union[nodes.List, nodes.Tuple]) -> None:
+        if not node.elts:
+            self._ignore.append(node)
+        elif all(isinstance(e, nodes.Const) for e in node.elts):
+            self._ignore.append(node)
+
+    def visit_list(self, node: nodes.List) -> None:
+        self._visit_sequence(node)
+
+    def visit_tuple(self, node: nodes.Tuple) -> None:
+        self._visit_sequence(node)
+
+    def visit_dict(self, node: nodes.Dict) -> None:
+        if not node.items:
+            self._ignore.append(node)
+        elif all(
+            isinstance(k, nodes.Const) and isinstance(v, nodes.Const)
+            for k, v in node.items
+        ):
+            self._ignore.append(node)
+
     @checker_utils.check_messages("loop-invariant-statement")
     def leave_for(self, node: nodes.For) -> None:
         self._leave_loop(node)

tests/test_loop_invariant.py

@@ -279,15 +279,32 @@ def test(): #@
         with self.assertNoMessages():
             self.walk(test_func)
 
-    # TODO : Fix constant checks
-    # def test_constants(self):
-    #     test_func = astroid.extract_node(
-    #         """
-    #     def test(): #@
-    #         for _ in fruits:
-    #             fruits = ["apple", "banana", "pear"]
-    #     """
-    #     )
-
-    #     with self.assertNoMessages():
-    #         self.walk(test_func)
+    def test_constants(self):
+        test_func = astroid.extract_node(
+            """
+        def test(): #@
+            for _ in fruits:
+                fruits = ["apple", "banana", "pear"]
+                fruits_tuple = ("apple", "banana", "pear")
+                _ = []
+                _ = [1, 2, 3]
+                _ = ()
+                _ = (1, 2, 3)
+        """
+        )
+
+        with self.assertNoMessages():
+            self.walk(test_func)
+
+    def test_constant_dictionaries(self):
+        test_func = astroid.extract_node(
+            """
+        def test(): #@
+            for _ in fruits:
+                _ = {}
+                fruits = {0: 1, 1: 2}
+        """
+        )
+
+        with self.assertNoMessages():
+            self.walk(test_func)