splat nodes

Author: clavedeluna

doc/whatsnew/fragments/8168.bugfix

@@ -0,0 +1,3 @@
+Fix ``nested-min-max`` suggestion message to indicate it's possible to splat iterable objects.
+
+Closes #8168

pylint/checkers/nested_min_max.py

@@ -12,7 +12,7 @@
 from astroid import nodes
 
 from pylint.checkers import BaseChecker
-from pylint.checkers.utils import only_required_for_messages, safe_infer
+from pylint.checkers.utils import DICT_TYPES, only_required_for_messages, safe_infer
 from pylint.interfaces import INFERENCE
 
 if TYPE_CHECKING:
@@ -83,6 +83,20 @@ def visit_call(self, node: nodes.Call) -> None:
 
             redundant_calls = self.get_redundant_calls(fixed_node)
 
+        for idx, arg in enumerate(fixed_node.args):
+            if not isinstance(arg, nodes.Const):
+                inferred = safe_infer(arg)
+                if isinstance(
+                    inferred, (nodes.List, nodes.Tuple, nodes.Set, *DICT_TYPES)
+                ):
+                    splat_node = nodes.Starred(lineno=inferred.lineno)
+                    splat_node.value = arg
+                    fixed_node.args = (
+                        fixed_node.args[:idx]
+                        + [splat_node]
+                        + fixed_node.args[idx + 1 : idx]
+                    )
+
         self.add_message(
             "nested-min-max",
             node=node,

pylint/checkers/utils.py

@@ -238,6 +238,13 @@
     {"_sitebuiltins.Quitter", "sys.exit", "posix._exit", "nt._exit"}
 )
 
+DICT_TYPES = (
+    astroid.objects.DictValues,
+    astroid.objects.DictKeys,
+    astroid.objects.DictItems,
+    astroid.nodes.node_classes.Dict,
+)
+
 
 class NoSuchArgumentError(Exception):
     pass

pylint/checkers/variables.py

@@ -108,13 +108,6 @@
     }
 )
 
-DICT_TYPES = (
-    astroid.objects.DictValues,
-    astroid.objects.DictKeys,
-    astroid.objects.DictItems,
-    astroid.nodes.node_classes.Dict,
-)
-
 
 class VariableVisitConsumerAction(Enum):
     """Reported by _check_consumer() and its sub-methods to determine the
@@ -166,7 +159,7 @@ def _get_unpacking_extra_info(node: nodes.Assign, inferred: InferenceResult) ->
     and unbalanced-tuple/dict-unpacking errors.
     """
     more = ""
-    if isinstance(inferred, DICT_TYPES):
+    if isinstance(inferred, utils.DICT_TYPES):
         if isinstance(node, nodes.Assign):
             more = node.value.as_string()
         elif isinstance(node, nodes.For):
@@ -1249,7 +1242,7 @@ def visit_for(self, node: nodes.For) -> None:
         targets = node.target.elts
 
         inferred = utils.safe_infer(node.iter)
-        if not isinstance(inferred, DICT_TYPES):
+        if not isinstance(inferred, utils.DICT_TYPES):
             return
 
         values = self._nodes_to_unpack(inferred)
@@ -2886,7 +2879,7 @@ def _check_unpacking(
     @staticmethod
     def _nodes_to_unpack(node: nodes.NodeNG) -> list[nodes.NodeNG] | None:
         """Return the list of values of the `Assign` node."""
-        if isinstance(node, (nodes.Tuple, nodes.List) + DICT_TYPES):
+        if isinstance(node, (nodes.Tuple, nodes.List) + utils.DICT_TYPES):
             return node.itered()  # type: ignore[no-any-return]
         if isinstance(node, astroid.Instance) and any(
             ancestor.qname() == "typing.NamedTuple" for ancestor in node.ancestors()
@@ -2912,7 +2905,7 @@ def _report_unbalanced_unpacking(
 
         symbol = (
             "unbalanced-dict-unpacking"
-            if isinstance(inferred, DICT_TYPES)
+            if isinstance(inferred, utils.DICT_TYPES)
             else "unbalanced-tuple-unpacking"
         )
         self.add_message(symbol, node=node, args=args, confidence=INFERENCE)

tests/functional/n/nested_min_max.py

@@ -19,3 +19,26 @@
 # This is too complicated (for now) as there is no clear better way to write it
 max(max(i for i in range(10)), 0)
 max(max(max(i for i in range(10)), 0), 1)
+
+# These examples can be improved by splicing
+lst = [1, 2]
+max(3, max(lst))  # [nested-min-max]
+max(3, *lst)
+
+nums = (1, 2,)
+max(3, max(nums))  # [nested-min-max]
+max(3, *nums)
+
+nums = {1, 2}
+max(3, max(nums))  # [nested-min-max]
+max(3, *nums)
+
+nums = {1: 2, 7: 10}
+max(3, max(nums))  # [nested-min-max]
+max(3, *nums)
+
+max(3, max(nums.values()))  # [nested-min-max]
+max(3, *nums.values())
+
+lst2 = [3, 7, 10]
+max(3, max(nums), max(lst2))  # [nested-min-max]

tests/functional/n/nested_min_max.txt

@@ -6,3 +6,9 @@ nested-min-max:8:0:8:25::Do not use nested call of 'min'; it's possible to do 'm
 nested-min-max:11:0:11:25::Do not use nested call of 'min'; it's possible to do 'min(1, 2, 3, 4)' instead:INFERENCE
 nested-min-max:12:0:12:40::Do not use nested call of 'min'; it's possible to do 'min(len([]), len([1]), len([1, 2]))' instead:INFERENCE
 nested-min-max:17:0:17:27::Do not use nested call of 'orig_min'; it's possible to do 'orig_min(1, 2, 3)' instead:INFERENCE
+nested-min-max:25:0:25:16::Do not use nested call of 'max'; it's possible to do 'max(3, *lst)' instead:INFERENCE
+nested-min-max:29:0:29:17::Do not use nested call of 'max'; it's possible to do 'max(3, *nums)' instead:INFERENCE
+nested-min-max:33:0:33:17::Do not use nested call of 'max'; it's possible to do 'max(3, *nums)' instead:INFERENCE
+nested-min-max:37:0:37:17::Do not use nested call of 'max'; it's possible to do 'max(3, *nums)' instead:INFERENCE
+nested-min-max:40:0:40:26::Do not use nested call of 'max'; it's possible to do 'max(3, *nums.values())' instead:INFERENCE
+nested-min-max:44:0:44:28::Do not use nested call of 'max'; it's possible to do 'max(3, *nums, *lst2)' instead:INFERENCE

tests/regrtest_data/nested_min_max.py

@@ -0,0 +1,18 @@
+"""All of these nested-min-max messages should suggest splatting."""
+
+lst = [1, 2]
+max(3, max(lst))  # [nested-min-max]
+
+nums = (1, 2,)
+max(3, max(nums))  # [nested-min-max]
+
+nums = {1, 2}
+max(3, max(nums))  # [nested-min-max]
+
+nums = {1: 2, 7: 10}
+max(3, max(nums))  # [nested-min-max]
+
+max(3, max(nums.values()))  # [nested-min-max]
+
+lst2 = [3, 7, 10]
+max(3, max(nums), max(lst2))  # [nested-min-max]

tests/test_self.py

@@ -1302,6 +1302,21 @@ def test_no_name_in_module(self) -> None:
             [module, "-E"], expected_output="", unexpected_output=unexpected
         )
 
+    def test_nested_min_max_splats(self) -> None:
+        """Test that the nested-min-max message suggests to splat an iterable"""
+        module = join(HERE, "regrtest_data", "nested_min_max.py")
+        expected_str = f"""
+        ************* Module nested_min_max
+        {module}:4:0: W3301: Do not use nested call of 'max'; it's possible to do 'max(3, *lst)' instead (nested-min-max)
+        {module}:7:0: W3301: Do not use nested call of 'max'; it's possible to do 'max(3, *nums)' instead (nested-min-max)
+        {module}:10:0: W3301: Do not use nested call of 'max'; it's possible to do 'max(3, *nums)' instead (nested-min-max)
+        {module}:13:0: W3301: Do not use nested call of 'max'; it's possible to do 'max(3, *nums)' instead (nested-min-max)
+        {module}:15:0: W3301: Do not use nested call of 'max'; it's possible to do 'max(3, *nums.values())' instead (nested-min-max)
+        {module}:18:0: W3301: Do not use nested call of 'max'; it's possible to do 'max(3, *nums, *lst2)' instead (nested-min-max)
+        """  # noqa: E501
+        expected = textwrap.dedent(expected_str)
+        self._test_output([module], expected_output=expected)
+
 
 class TestCallbackOptions:
     """Test for all callback options we support."""