Emit consider-using-tuple for in comparisons

ChangeLog

@@ -11,6 +11,11 @@ Release date: TBA
   Put new features here and also in 'doc/whatsnew/2.11.rst'
 
 
+* ``CodeStyleChecker``
+
+  * Emit ``consider-using-tuple`` for ``in`` comparisons when a ``list`` is used.
+
+
 What's New in Pylint 2.10.1?
 ============================
 Release date: TBA

doc/whatsnew/2.11.rst

@@ -16,6 +16,10 @@ New checkers
 Extensions
 ==========
 
+* ``CodeStyleChecker``
+
+  * Emit ``consider-using-tuple`` for ``in`` comparisons when a ``list`` is used.
+
 
 Other Changes
 =============

pylint/checkers/classes.py

@@ -1000,10 +1000,10 @@ def _check_unused_private_attributes(self, node: nodes.ClassDef) -> None:
                 if attribute.attrname != assign_attr.attrname:
                     continue
 
-                if assign_attr.expr.name == "cls" and attribute.expr.name in [
+                if assign_attr.expr.name == "cls" and attribute.expr.name in (
                     "cls",
                     "self",
-                ]:
+                ):
                     # If assigned to cls.attrib, can be accessed by cls/self
                     break
 

pylint/checkers/python3.py

@@ -157,7 +157,7 @@ def _in_iterating_context(node):
     elif (
         isinstance(parent, nodes.Compare)
         and len(parent.ops) == 1
-        and parent.ops[0][0] in ["in", "not in"]
+        and parent.ops[0][0] in ("in", "not in")
     ):
         return True
     # Also if it's an `yield from`, that's fair

pylint/checkers/refactoring/refactoring_checker.py

@@ -966,7 +966,7 @@ def _check_consider_using_generator(self, node):
                 # remove square brackets '[]'
                 inside_comp = node.args[0].as_string()[1:-1]
                 call_name = node.func.name
-                if call_name in ["any", "all"]:
+                if call_name in ("any", "all"):
                     self.add_message(
                         "use-a-generator",
                         node=node,

pylint/checkers/stdlib.py

@@ -566,7 +566,7 @@ def _check_redundant_assert(self, node, infer):
             isinstance(infer, astroid.BoundMethod)
             and node.args
             and isinstance(node.args[0], nodes.Const)
-            and infer.name in ["assertTrue", "assertFalse"]
+            and infer.name in ("assertTrue", "assertFalse")
         ):
             self.add_message(
                 "redundant-unittest-assert",

pylint/checkers/typecheck.py

@@ -517,7 +517,7 @@ def _emit_no_member(node, owner, owner_name, ignored_mixins=True, ignored_none=T
         and isinstance(owner.parent, nodes.ClassDef)
         and owner.parent.name == "EnumMeta"
         and owner_name == "__members__"
-        and node.attrname in ["items", "values", "keys"]
+        and node.attrname in ("items", "values", "keys")
     ):
         # Avoid false positive on Enum.__members__.{items(), values, keys}
         # See https://github.com/PyCQA/pylint/issues/4123
@@ -1778,7 +1778,7 @@ def visit_compare(self, node):
             return
 
         op, right = node.ops[0]
-        if op in ["in", "not in"]:
+        if op in ("in", "not in"):
             self._check_membership_test(right)
 
     @check_messages(

pylint/extensions/code_style.py

@@ -61,6 +61,12 @@ def visit_comprehension(self, node: nodes.Comprehension) -> None:
         if isinstance(node.iter, nodes.List):
             self.add_message("consider-using-tuple", node=node.iter)
 
+    @check_messages("consider-using-tuple")
+    def visit_compare(self, node: nodes.Compare) -> None:
+        for op, comparator in node.ops:
+            if op == "in" and isinstance(comparator, nodes.List):
+                self.add_message("consider-using-tuple", node=comparator)
+
     def _check_dict_consider_namedtuple_dataclass(self, node: nodes.Dict) -> None:
         """Check if dictionary values can be replaced by Namedtuple or Dataclass."""
         if not (

pylint/lint/pylinter.py

@@ -728,7 +728,7 @@ def any_fail_on_issues(self):
     def disable_noerror_messages(self):
         for msgcat, msgids in self.msgs_store._msgs_by_category.items():
             # enable only messages with 'error' severity and above ('fatal')
-            if msgcat in ["E", "F"]:
+            if msgcat in ("E", "F"):
                 for msgid in msgids:
                     self.enable(msgid)
             else:

script/bump_changelog.py

@@ -136,7 +136,7 @@ def do_checks(content, next_version, version, version_type):
     wn_next_version = get_whats_new(next_version)
     wn_this_version = get_whats_new(version)
     # There is only one field where the release date is TBA
-    if version_type in [VersionType.MAJOR, VersionType.MINOR]:
+    if version_type in (VersionType.MAJOR, VersionType.MINOR):
         assert (
             content.count(RELEASE_DATE_TEXT) <= 1
         ), f"There should be only one release date 'TBA' ({version}) {err}"

tests/functional/ext/code_style/code_style_consider_using_tuple.py

@@ -29,3 +29,31 @@
 # Don't emit warning for sets as this is handled by builtin checker
 (x for x in {1, 2, 3})  # [use-sequence-for-iteration]
 [x for x in {*var, 2}]  # [use-sequence-for-iteration]
+
+
+# -----
+# Suggest tuple for `in` comparisons
+x in var
+x in {1, 2, 3}
+x in (1, 2, 3)
+x in [1, 2, 3]  # [consider-using-tuple]
+
+if x in var:
+    pass
+if x in {1, 2, 3}:
+    pass
+if x in (1, 2, 3):
+    pass
+if x in [1, 2, 3]:  # [consider-using-tuple]
+    pass
+
+42 if x in [1, 2, 3] else None  # [consider-using-tuple]
+assert x in [1, 2, 3]  # [consider-using-tuple]
+(x for x in var if x in [1, 2, 3])  # [consider-using-tuple]
+while x in [1, 2, 3]:  # [consider-using-tuple]
+    break
+
+# Stacked operators, rightmost pair is evaluated first
+# Doesn't make much sense in practice since `in` will only return `bool`
+True == x in [1, 2, 3]  # [consider-using-tuple]  # noqa: E712
+1 >= x in [1, 2, 3]  # [consider-using-tuple]  # noqa: E712

tests/functional/ext/code_style/code_style_consider_using_tuple.txt

@@ -6,3 +6,11 @@ consider-using-tuple:23:9::Consider using an in-place tuple instead of list
 consider-using-tuple:26:12::Consider using an in-place tuple instead of list
 use-sequence-for-iteration:30:12::Use a sequence type when iterating over values
 use-sequence-for-iteration:31:12::Use a sequence type when iterating over values
+consider-using-tuple:39:5::Consider using an in-place tuple instead of list
+consider-using-tuple:47:8::Consider using an in-place tuple instead of list
+consider-using-tuple:50:11::Consider using an in-place tuple instead of list
+consider-using-tuple:51:12::Consider using an in-place tuple instead of list
+consider-using-tuple:52:24::Consider using an in-place tuple instead of list
+consider-using-tuple:53:11::Consider using an in-place tuple instead of list
+consider-using-tuple:58:13::Consider using an in-place tuple instead of list
+consider-using-tuple:59:10::Consider using an in-place tuple instead of list