[pylint] Add duplicate-bases rule

crates/ruff/resources/test/fixtures/pylint/duplicate_bases.py

@@ -0,0 +1,24 @@
+###
+# Errors.
+###
+class A:
+    ...
+
+
+class B(A, A):
+    ...
+
+
+###
+# Non-errors.
+###
+class C:
+    ...
+
+
+class D(C):
+    ...
+
+
+class E(A, C):
+    ...

crates/ruff/src/checkers/ast/mod.rs

@@ -761,6 +761,10 @@ where
                 if self.settings.rules.enabled(Rule::BuiltinVariableShadowing) {
                     flake8_builtins::rules::builtin_variable_shadowing(self, name, stmt);
                 }
+
+                if self.settings.rules.enabled(Rule::DuplicateBases) {
+                    pylint::rules::duplicate_bases(self, name, bases);
+                }
             }
             StmtKind::Import(ast::StmtImport { names }) => {
                 if self.settings.rules.enabled(Rule::MultipleImportsOnOneLine) {

crates/ruff/src/codes.rs

@@ -213,6 +213,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<Rule> {
         (Pylint, "W2901") => Rule::RedefinedLoopName,
         (Pylint, "E0302") => Rule::UnexpectedSpecialMethodSignature,
         (Pylint, "W3301") => Rule::NestedMinMax,
+        (Pylint, "E0241") => Rule::DuplicateBases,
 
         // flake8-builtins
         (Flake8Builtins, "001") => Rule::BuiltinVariableShadowing,

crates/ruff/src/registry.rs

@@ -190,6 +190,7 @@ ruff_macros::register_rules!(
     rules::pylint::rules::LoggingTooManyArgs,
     rules::pylint::rules::UnexpectedSpecialMethodSignature,
     rules::pylint::rules::NestedMinMax,
+    rules::pylint::rules::DuplicateBases,
     // flake8-builtins
     rules::flake8_builtins::rules::BuiltinVariableShadowing,
     rules::flake8_builtins::rules::BuiltinArgumentShadowing,

crates/ruff/src/rules/pylint/mod.rs

@@ -46,6 +46,7 @@ mod tests {
     #[test_case(Rule::ImportSelf, Path::new("import_self/module.py"); "PLW0406")]
     #[test_case(Rule::InvalidAllFormat, Path::new("invalid_all_format.py"); "PLE0605")]
     #[test_case(Rule::InvalidAllObject, Path::new("invalid_all_object.py"); "PLE0604")]
+    #[test_case(Rule::DuplicateBases, Path::new("duplicate_bases.py"); "PLE0241")]
     #[test_case(Rule::InvalidCharacterBackspace, Path::new("invalid_characters.py"); "PLE2510")]
     #[test_case(Rule::InvalidCharacterEsc, Path::new("invalid_characters.py"); "PLE2513")]
     #[test_case(Rule::InvalidCharacterNul, Path::new("invalid_characters.py"); "PLE2514")]

crates/ruff/src/rules/pylint/rules/duplicate_bases.rs

@@ -0,0 +1,42 @@
+use std::hash::BuildHasherDefault;
+
+use rustc_hash::FxHashSet;
+use rustpython_parser::ast::{self, Expr, ExprKind, Identifier};
+
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+
+use crate::checkers::ast::Checker;
+
+#[violation]
+pub struct DuplicateBases {
+    base: String,
+    class: String,
+}
+
+impl Violation for DuplicateBases {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let DuplicateBases { base, class } = self;
+        format!("Duplicate base `{base}` for class `{class}`")
+    }
+}
+
+/// PLE0241
+pub(crate) fn duplicate_bases(checker: &mut Checker, name: &str, bases: &[Expr]) {
+    let mut seen: FxHashSet<&Identifier> =
+        FxHashSet::with_capacity_and_hasher(bases.len(), BuildHasherDefault::default());
+    for base in bases {
+        if let ExprKind::Name(ast::ExprName { id, .. }) = &base.node {
+            if !seen.insert(id) {
+                checker.diagnostics.push(Diagnostic::new(
+                    DuplicateBases {
+                        base: id.to_string(),
+                        class: name.to_string(),
+                    },
+                    base.range(),
+                ));
+            }
+        }
+    }
+}

crates/ruff/src/rules/pylint/rules/mod.rs

@@ -8,6 +8,7 @@ pub(crate) use collapsible_else_if::{collapsible_else_if, CollapsibleElseIf};
 pub(crate) use compare_to_empty_string::{compare_to_empty_string, CompareToEmptyString};
 pub(crate) use comparison_of_constant::{comparison_of_constant, ComparisonOfConstant};
 pub(crate) use continue_in_finally::{continue_in_finally, ContinueInFinally};
+pub(crate) use duplicate_bases::{duplicate_bases, DuplicateBases};
 pub(crate) use global_statement::{global_statement, GlobalStatement};
 pub(crate) use global_variable_not_assigned::GlobalVariableNotAssigned;
 pub(crate) use import_self::{import_from_self, import_self, ImportSelf};
@@ -57,6 +58,7 @@ mod collapsible_else_if;
 mod compare_to_empty_string;
 mod comparison_of_constant;
 mod continue_in_finally;
+mod duplicate_bases;
 mod global_statement;
 mod global_variable_not_assigned;
 mod import_self;

crates/ruff/src/rules/pylint/snapshots/ruff__rules__pylint__tests__PLE0241_duplicate_bases.py.snap

@@ -0,0 +1,11 @@
+---
+source: crates/ruff/src/rules/pylint/mod.rs
+---
+duplicate_bases.py:8:12: PLE0241 Duplicate base `A` for class `B`
+  |
+8 | class B(A, A):
+  |            ^ PLE0241
+9 |     ...
+  |
+
+