Fixed false positive nested-min-max for nested lists (#9323) (#9337)

Nesting is useful for finding the maximum in a matrix. Therefore, pylint allows nesting of the form: max(max([[1, 2, 3], [4, 5, 6]])) Closes #9307 Co-authored-by: Pierre Sassoulas <[email protected]> (cherry picked from commit da13c74) Co-authored-by: Udi Fuchs <[email protected]>
pylint-dev · Dec 30, 2023 · 015c43a · 015c43a
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diff --git a/doc/whatsnew/fragments/9307.false_positive b/doc/whatsnew/fragments/9307.false_positive
@@ -0,0 +1,3 @@
+Fixed false positive nested-min-max for nested lists.
+
+Closes #9307
diff --git a/pylint/checkers/nested_min_max.py b/pylint/checkers/nested_min_max.py
@@ -62,7 +62,14 @@ def get_redundant_calls(cls, node: nodes.Call) -> list[nodes.Call]:
         return [
             arg
             for arg in node.args
-            if cls.is_min_max_call(arg) and arg.func.name == node.func.name
+            if (
+                cls.is_min_max_call(arg)
+                and arg.func.name == node.func.name
+                # Nesting is useful for finding the maximum in a matrix.
+                # Allow: max(max([[1, 2, 3], [4, 5, 6]]))
+                # Meaning, redundant call only if parent max call has more than 1 arg.
+                and len(arg.parent.args) > 1
+            )
         ]
 
     @only_required_for_messages("nested-min-max")

diff --git a/tests/functional/n/nested_min_max.py b/tests/functional/n/nested_min_max.py
@@ -54,3 +54,11 @@
 
 max(3, max(list(range(4))))  # [nested-min-max]
 max(3, *list(range(4)))
+
+# Nesting is useful for finding the maximum in a matrix
+# No message if external call has exactly 1 argument
+matrix = [[1, 2, 3], [4, 5, 6]]
+max(max(matrix))
+max(max(max(matrix)))
+max(3, max(max(matrix)))  # [nested-min-max]
+max(max(3, max(matrix)))  # [nested-min-max]
diff --git a/tests/functional/n/nested_min_max.txt b/tests/functional/n/nested_min_max.txt
@@ -16,3 +16,5 @@ nested-min-max:46:0:46:25::Do not use nested call of 'max'; it's possible to do
 nested-min-max:49:0:49:45::Do not use nested call of 'max'; it's possible to do 'max(3, *[5] + [i for i in range(4) if i])' instead:INFERENCE
 nested-min-max:52:0:52:33::Do not use nested call of 'max'; it's possible to do 'max(3, *[5] + list(range(4)))' instead:INFERENCE
 nested-min-max:55:0:55:27::Do not use nested call of 'max'; it's possible to do 'max(3, *list(range(4)))' instead:INFERENCE
+nested-min-max:63:0:63:24::Do not use nested call of 'max'; it's possible to do 'max(3, max(matrix))' instead:INFERENCE
+nested-min-max:64:4:64:23::Do not use nested call of 'max'; it's possible to do 'max(3, *matrix)' instead:INFERENCE