[pylint] Implement assigning-non-slot (E0237) (#9623)

## Summary

Implement [assigning-non-slot /
E0237](https://pylint.readthedocs.io/en/latest/user_guide/messages/error/assigning-non-slot.html)

related #970

## Test Plan

`cargo test`

crates/ruff_linter/resources/test/fixtures/pylint/non_slot_assignment.py

@@ -0,0 +1,56 @@
+class StudentA:
+    __slots__ = ("name",)
+
+    def __init__(self, name, surname):
+        self.name = name
+        self.surname = surname  # [assigning-non-slot]
+        self.setup()
+
+    def setup(self):
+        pass
+
+
+class StudentB:
+    __slots__ = ("name", "surname")
+
+    def __init__(self, name, middle_name):
+        self.name = name
+        self.middle_name = middle_name  # [assigning-non-slot]
+        self.setup()
+
+    def setup(self):
+        pass
+
+
+class StudentC:
+    __slots__ = ("name", "surname")
+
+    def __init__(self, name, surname):
+        self.name = name
+        self.surname = surname  # OK
+        self.setup()
+
+    def setup(self):
+        pass
+
+
+class StudentD(object):
+    __slots__ = ("name", "surname")
+
+    def __init__(self, name, middle_name):
+        self.name = name
+        self.middle_name = middle_name  # [assigning-non-slot]
+        self.setup()
+
+    def setup(self):
+        pass
+
+
+class StudentE(StudentD):
+    def __init__(self, name, middle_name):
+        self.name = name
+        self.middle_name = middle_name  # OK
+        self.setup()
+
+    def setup(self):
+        pass

crates/ruff_linter/src/checkers/ast/analyze/statement.rs

@@ -507,6 +507,9 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
             if checker.enabled(Rule::NoSlotsInNamedtupleSubclass) {
                 flake8_slots::rules::no_slots_in_namedtuple_subclass(checker, stmt, class_def);
             }
+            if checker.enabled(Rule::NonSlotAssignment) {
+                pylint::rules::non_slot_assignment(checker, class_def);
+            }
             if checker.enabled(Rule::SingleStringSlots) {
                 pylint::rules::single_string_slots(checker, class_def);
             }

crates/ruff_linter/src/codes.rs

@@ -224,6 +224,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pylint, "E0116") => (RuleGroup::Stable, rules::pylint::rules::ContinueInFinally),
         (Pylint, "E0117") => (RuleGroup::Stable, rules::pylint::rules::NonlocalWithoutBinding),
         (Pylint, "E0118") => (RuleGroup::Stable, rules::pylint::rules::LoadBeforeGlobalDeclaration),
+        (Pylint, "E0237") => (RuleGroup::Stable, rules::pylint::rules::NonSlotAssignment),
         (Pylint, "E0241") => (RuleGroup::Stable, rules::pylint::rules::DuplicateBases),
         (Pylint, "E0302") => (RuleGroup::Stable, rules::pylint::rules::UnexpectedSpecialMethodSignature),
         (Pylint, "E0307") => (RuleGroup::Stable, rules::pylint::rules::InvalidStrReturnType),

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

@@ -92,6 +92,7 @@ mod tests {
         Path::new("named_expr_without_context.py")
     )]
     #[test_case(Rule::NonlocalWithoutBinding, Path::new("nonlocal_without_binding.py"))]
+    #[test_case(Rule::NonSlotAssignment, Path::new("non_slot_assignment.py"))]
     #[test_case(Rule::PropertyWithParameters, Path::new("property_with_parameters.py"))]
     #[test_case(
         Rule::RedefinedArgumentFromLocal,

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

@@ -41,6 +41,7 @@ pub(crate) use no_method_decorator::*;
 pub(crate) use no_self_use::*;
 pub(crate) use non_ascii_module_import::*;
 pub(crate) use non_ascii_name::*;
+pub(crate) use non_slot_assignment::*;
 pub(crate) use nonlocal_without_binding::*;
 pub(crate) use potential_index_error::*;
 pub(crate) use property_with_parameters::*;
@@ -124,6 +125,7 @@ mod no_method_decorator;
 mod no_self_use;
 mod non_ascii_module_import;
 mod non_ascii_name;
+mod non_slot_assignment;
 mod nonlocal_without_binding;
 mod potential_index_error;
 mod property_with_parameters;

crates/ruff_linter/src/rules/pylint/rules/non_slot_assignment.rs

@@ -0,0 +1,242 @@
+use rustc_hash::FxHashSet;
+
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::{self as ast, Expr, Stmt};
+use ruff_text_size::{Ranged, TextRange};
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for assignments to attributes that are not defined in `__slots__`.
+///
+/// ## Why is this bad?
+/// When using `__slots__`, only the specified attributes are allowed.
+/// Attempting to assign to an attribute that is not defined in `__slots__`
+/// will result in an `AttributeError` at runtime.
+///
+/// ## Known problems
+/// This rule can't detect `__slots__` implementations in superclasses, and
+/// so limits its analysis to classes that inherit from (at most) `object`.
+///
+/// ## Example
+/// ```python
+/// class Student:
+///     __slots__ = ("name",)
+///
+///     def __init__(self, name, surname):
+///         self.name = name
+///         self.surname = surname  # [assigning-non-slot]
+///         self.setup()
+///
+///     def setup(self):
+///         pass
+/// ```
+///
+/// Use instead:
+/// ```python
+/// class Student:
+///     __slots__ = ("name", "surname")
+///
+///     def __init__(self, name, surname):
+///         self.name = name
+///         self.surname = surname
+///         self.setup()
+///
+///     def setup(self):
+///         pass
+/// ```
+#[violation]
+pub struct NonSlotAssignment {
+    name: String,
+}
+
+impl Violation for NonSlotAssignment {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let NonSlotAssignment { name } = self;
+        format!("Attribute `{name}` is not defined in class's `__slots__`")
+    }
+}
+
+/// E0237
+pub(crate) fn non_slot_assignment(checker: &mut Checker, class_def: &ast::StmtClassDef) {
+    // If the class inherits from another class (aside from `object`), then it's possible that
+    // the parent class defines the relevant `__slots__`.
+    if !class_def.bases().iter().all(|base| {
+        checker
+            .semantic()
+            .resolve_call_path(base)
+            .is_some_and(|call_path| matches!(call_path.as_slice(), ["", "object"]))
+    }) {
+        return;
+    }
+
+    for attribute in is_attributes_not_in_slots(&class_def.body) {
+        checker.diagnostics.push(Diagnostic::new(
+            NonSlotAssignment {
+                name: attribute.name.to_string(),
+            },
+            attribute.range(),
+        ));
+    }
+}
+
+#[derive(Debug)]
+struct AttributeAssignment<'a> {
+    /// The name of the attribute that is assigned to.
+    name: &'a str,
+    /// The range of the attribute that is assigned to.
+    range: TextRange,
+}
+
+impl Ranged for AttributeAssignment<'_> {
+    fn range(&self) -> TextRange {
+        self.range
+    }
+}
+
+/// Return a list of attributes that are assigned to but not included in `__slots__`.
+fn is_attributes_not_in_slots(body: &[Stmt]) -> Vec<AttributeAssignment> {
+    // First, collect all the attributes that are assigned to `__slots__`.
+    let mut slots = FxHashSet::default();
+    for statement in body {
+        match statement {
+            // Ex) `__slots__ = ("name",)`
+            Stmt::Assign(ast::StmtAssign { targets, value, .. }) => {
+                let [Expr::Name(ast::ExprName { id, .. })] = targets.as_slice() else {
+                    continue;
+                };
+
+                if id == "__slots__" {
+                    slots.extend(slots_attributes(value));
+                }
+            }
+
+            // Ex) `__slots__: Tuple[str, ...] = ("name",)`
+            Stmt::AnnAssign(ast::StmtAnnAssign {
+                target,
+                value: Some(value),
+                ..
+            }) => {
+                let Expr::Name(ast::ExprName { id, .. }) = target.as_ref() else {
+                    continue;
+                };
+
+                if id == "__slots__" {
+                    slots.extend(slots_attributes(value));
+                }
+            }
+
+            // Ex) `__slots__ += ("name",)`
+            Stmt::AugAssign(ast::StmtAugAssign { target, value, .. }) => {
+                let Expr::Name(ast::ExprName { id, .. }) = target.as_ref() else {
+                    continue;
+                };
+
+                if id == "__slots__" {
+                    slots.extend(slots_attributes(value));
+                }
+            }
+            _ => {}
+        }
+    }
+
+    if slots.is_empty() {
+        return vec![];
+    }
+
+    // Second, find any assignments that aren't included in `__slots__`.
+    let mut assignments = vec![];
+    for statement in body {
+        let Stmt::FunctionDef(ast::StmtFunctionDef { name, body, .. }) = statement else {
+            continue;
+        };
+
+        if name == "__init__" {
+            for statement in body {
+                match statement {
+                    // Ex) `self.name = name`
+                    Stmt::Assign(ast::StmtAssign { targets, .. }) => {
+                        let [Expr::Attribute(attribute)] = targets.as_slice() else {
+                            continue;
+                        };
+                        let Expr::Name(ast::ExprName { id, .. }) = attribute.value.as_ref() else {
+                            continue;
+                        };
+                        if id == "self" && !slots.contains(attribute.attr.as_str()) {
+                            assignments.push(AttributeAssignment {
+                                name: &attribute.attr,
+                                range: attribute.range(),
+                            });
+                        }
+                    }
+
+                    // Ex) `self.name: str = name`
+                    Stmt::AnnAssign(ast::StmtAnnAssign { target, .. }) => {
+                        let Expr::Attribute(attribute) = target.as_ref() else {
+                            continue;
+                        };
+                        let Expr::Name(ast::ExprName { id, .. }) = attribute.value.as_ref() else {
+                            continue;
+                        };
+                        if id == "self" && !slots.contains(attribute.attr.as_str()) {
+                            assignments.push(AttributeAssignment {
+                                name: &attribute.attr,
+                                range: attribute.range(),
+                            });
+                        }
+                    }
+
+                    // Ex) `self.name += name`
+                    Stmt::AugAssign(ast::StmtAugAssign { target, .. }) => {
+                        let Expr::Attribute(attribute) = target.as_ref() else {
+                            continue;
+                        };
+                        let Expr::Name(ast::ExprName { id, .. }) = attribute.value.as_ref() else {
+                            continue;
+                        };
+                        if id == "self" && !slots.contains(attribute.attr.as_str()) {
+                            assignments.push(AttributeAssignment {
+                                name: &attribute.attr,
+                                range: attribute.range(),
+                            });
+                        }
+                    }
+
+                    _ => {}
+                }
+            }
+        }
+    }
+
+    assignments
+}
+
+/// Return an iterator over the attributes enumerated in the given `__slots__` value.
+fn slots_attributes(expr: &Expr) -> impl Iterator<Item = &str> {
+    // Ex) `__slots__ = ("name",)`
+    let elts_iter = match expr {
+        Expr::Tuple(ast::ExprTuple { elts, .. })
+        | Expr::List(ast::ExprList { elts, .. })
+        | Expr::Set(ast::ExprSet { elts, .. }) => Some(elts.iter().filter_map(|elt| match elt {
+            Expr::StringLiteral(ast::ExprStringLiteral { value, .. }) => Some(value.to_str()),
+            _ => None,
+        })),
+        _ => None,
+    };
+
+    // Ex) `__slots__ = {"name": ...}`
+    let keys_iter = match expr {
+        Expr::Dict(ast::ExprDict { keys, .. }) => Some(keys.iter().filter_map(|key| match key {
+            Some(Expr::StringLiteral(ast::ExprStringLiteral { value, .. })) => Some(value.to_str()),
+            _ => None,
+        })),
+        _ => None,
+    };
+
+    elts_iter
+        .into_iter()
+        .flatten()
+        .chain(keys_iter.into_iter().flatten())
+}

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLE0237_non_slot_assignment.py.snap

@@ -0,0 +1,31 @@
+---
+source: crates/ruff_linter/src/rules/pylint/mod.rs
+---
+non_slot_assignment.py:6:9: PLE0237 Attribute `surname` is not defined in class's `__slots__`
+  |
+4 |     def __init__(self, name, surname):
+5 |         self.name = name
+6 |         self.surname = surname  # [assigning-non-slot]
+  |         ^^^^^^^^^^^^ PLE0237
+7 |         self.setup()
+  |
+
+non_slot_assignment.py:18:9: PLE0237 Attribute `middle_name` is not defined in class's `__slots__`
+   |
+16 |     def __init__(self, name, middle_name):
+17 |         self.name = name
+18 |         self.middle_name = middle_name  # [assigning-non-slot]
+   |         ^^^^^^^^^^^^^^^^ PLE0237
+19 |         self.setup()
+   |
+
+non_slot_assignment.py:42:9: PLE0237 Attribute `middle_name` is not defined in class's `__slots__`
+   |
+40 |     def __init__(self, name, middle_name):
+41 |         self.name = name
+42 |         self.middle_name = middle_name  # [assigning-non-slot]
+   |         ^^^^^^^^^^^^^^^^ PLE0237
+43 |         self.setup()
+   |
+
+