[flake8-slots] Add plugin, add SLOT000, SLOT001 and SLOT002

LICENSE

@@ -354,6 +354,29 @@ are:
     SOFTWARE.
   """
 
+- flake8-slots, licensed as follows:
+  """
+    Copyright (c) 2021 Dominic Davis-Foster
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in all
+    copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+    DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+    OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+    OR OTHER DEALINGS IN THE SOFTWARE.
+  """
+
 - flake8-todos, licensed as follows:
   """
     Copyright (c) 2019 EclecticIQ. All rights reserved.

README.md

@@ -283,6 +283,7 @@ quality tools, including:
 - [flake8-return](https://pypi.org/project/flake8-return/)
 - [flake8-self](https://pypi.org/project/flake8-self/)
 - [flake8-simplify](https://pypi.org/project/flake8-simplify/)
+- [flake8-slots](https://pypi.org/project/flake8-slots/)
 - [flake8-super](https://pypi.org/project/flake8-super/)
 - [flake8-tidy-imports](https://pypi.org/project/flake8-tidy-imports/)
 - [flake8-todos](https://pypi.org/project/flake8-todos/)

crates/ruff/resources/test/fixtures/flake8_slots/SLOT000.py

@@ -0,0 +1,6 @@
+class Bad(str):  # SLOT000
+    pass
+
+
+class Good(str):  # Ok
+    __slots__ = ["foo"]

crates/ruff/resources/test/fixtures/flake8_slots/SLOT001.py

@@ -0,0 +1,21 @@
+class Bad(tuple):  # SLOT001
+    pass
+
+
+class Good(tuple):  # Ok
+    __slots__ = ("foo",)
+
+
+from typing import Tuple
+
+
+class Bad(Tuple):  # SLOT001
+    pass
+
+
+class Bad(Tuple[str, int, float]):  # SLOT001
+    pass
+
+
+class Good(Tuple[str, int, float]):  # OK
+    __slots__ = ("foo",)

crates/ruff/resources/test/fixtures/flake8_slots/SLOT002.py

@@ -0,0 +1,14 @@
+from collections import namedtuple
+from typing import NamedTuple
+
+
+class Bad(namedtuple("foo", ["str", "int"])):  # SLOT002
+    pass
+
+
+class Good(namedtuple("foo", ["str", "int"])):  # OK
+    __slots__ = ("foo",)
+
+
+class Good(NamedTuple):  # Ok
+    pass

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

@@ -48,9 +48,9 @@ use crate::rules::{
     flake8_debugger, flake8_django, flake8_errmsg, flake8_future_annotations, flake8_gettext,
     flake8_implicit_str_concat, flake8_import_conventions, flake8_logging_format, flake8_pie,
     flake8_print, flake8_pyi, flake8_pytest_style, flake8_raise, flake8_return, flake8_self,
-    flake8_simplify, flake8_tidy_imports, flake8_type_checking, flake8_unused_arguments,
-    flake8_use_pathlib, flynt, mccabe, numpy, pandas_vet, pep8_naming, pycodestyle, pydocstyle,
-    pyflakes, pygrep_hooks, pylint, pyupgrade, ruff, tryceratops,
+    flake8_simplify, flake8_slots, flake8_tidy_imports, flake8_type_checking,
+    flake8_unused_arguments, flake8_use_pathlib, flynt, mccabe, numpy, pandas_vet, pep8_naming,
+    pycodestyle, pydocstyle, pyflakes, pygrep_hooks, pylint, pyupgrade, ruff, tryceratops,
 };
 use crate::settings::types::PythonVersion;
 use crate::settings::{flags, Settings};
@@ -682,14 +682,16 @@ where
                     pylint::rules::return_in_init(self, stmt);
                 }
             }
-            Stmt::ClassDef(ast::StmtClassDef {
-                name,
-                bases,
-                keywords,
-                decorator_list,
-                body,
-                range: _,
-            }) => {
+            Stmt::ClassDef(
+                class_def @ ast::StmtClassDef {
+                    name,
+                    bases,
+                    keywords,
+                    decorator_list,
+                    body,
+                    range: _,
+                },
+            ) => {
                 if self.enabled(Rule::DjangoNullableModelStringField) {
                     self.diagnostics
                         .extend(flake8_django::rules::nullable_model_string_field(
@@ -818,6 +820,18 @@ where
                 if self.enabled(Rule::DuplicateBases) {
                     pylint::rules::duplicate_bases(self, name, bases);
                 }
+
+                if self.enabled(Rule::NoSlotsInStrSubclass) {
+                    flake8_slots::rules::no_slots_in_str_subclass(self, stmt, class_def);
+                }
+
+                if self.enabled(Rule::NoSlotsInTupleSubclass) {
+                    flake8_slots::rules::no_slots_in_tuple_subclass(self, stmt, class_def);
+                }
+
+                if self.enabled(Rule::NoSlotsInNamedtupleSubclass) {
+                    flake8_slots::rules::no_slots_in_namedtuple_subclass(self, stmt, class_def);
+                }
             }
             Stmt::Import(ast::StmtImport { names, range: _ }) => {
                 if self.enabled(Rule::MultipleImportsOnOneLine) {

crates/ruff/src/codes.rs

@@ -782,6 +782,11 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Flake8Fixme, "003") => (RuleGroup::Unspecified, rules::flake8_fixme::rules::LineContainsXxx),
         (Flake8Fixme, "004") => (RuleGroup::Unspecified, rules::flake8_fixme::rules::LineContainsHack),
 
+        // flake8-slots
+        (Flake8Slots, "000") => (RuleGroup::Unspecified, rules::flake8_slots::rules::NoSlotsInStrSubclass),
+        (Flake8Slots, "001") => (RuleGroup::Unspecified, rules::flake8_slots::rules::NoSlotsInTupleSubclass),
+        (Flake8Slots, "002") => (RuleGroup::Unspecified, rules::flake8_slots::rules::NoSlotsInNamedtupleSubclass),
+
         _ => return None,
     })
 }

crates/ruff/src/registry.rs

@@ -137,6 +137,9 @@ pub enum Linter {
     /// [flake8-self](https://pypi.org/project/flake8-self/)
     #[prefix = "SLF"]
     Flake8Self,
+    /// [flake8-slots](https://pypi.org/project/flake8-slots/)
+    #[prefix = "SLOT"]
+    Flake8Slots,
     /// [flake8-simplify](https://pypi.org/project/flake8-simplify/)
     #[prefix = "SIM"]
     Flake8Simplify,

crates/ruff/src/rules/flake8_slots/mod.rs

@@ -0,0 +1,27 @@
+//! Rules from [flake8-slots](https://pypi.org/project/flake8-slots/).
+pub(crate) mod rules;
+
+#[cfg(test)]
+mod tests {
+    use std::path::Path;
+
+    use anyhow::Result;
+    use test_case::test_case;
+
+    use crate::registry::Rule;
+    use crate::test::test_path;
+    use crate::{assert_messages, settings};
+
+    #[test_case(Rule::NoSlotsInStrSubclass, Path::new("SLOT000.py"))]
+    #[test_case(Rule::NoSlotsInTupleSubclass, Path::new("SLOT001.py"))]
+    #[test_case(Rule::NoSlotsInNamedtupleSubclass, Path::new("SLOT002.py"))]
+    fn rules(rule_code: Rule, path: &Path) -> Result<()> {
+        let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());
+        let diagnostics = test_path(
+            Path::new("flake8_slots").join(path).as_path(),
+            &settings::Settings::for_rule(rule_code),
+        )?;
+        assert_messages!(snapshot, diagnostics);
+        Ok(())
+    }
+}

crates/ruff/src/rules/flake8_slots/rules/helpers.rs

@@ -0,0 +1,27 @@
+use rustpython_parser::ast::{self, Expr, Stmt};
+
+/// Return `true` if the given body contains a `__slots__` assignment.
+pub(super) fn has_slots(body: &[Stmt]) -> bool {
+    for stmt in body {
+        match stmt {
+            Stmt::Assign(ast::StmtAssign { targets, .. }) => {
+                for target in targets {
+                    if let Expr::Name(ast::ExprName { id, .. }) = target {
+                        if id.as_str() == "__slots__" {
+                            return true;
+                        }
+                    }
+                }
+            }
+            Stmt::AnnAssign(ast::StmtAnnAssign { target, .. }) => {
+                if let Expr::Name(ast::ExprName { id, .. }) = target.as_ref() {
+                    if id.as_str() == "__slots__" {
+                        return true;
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+    false
+}

crates/ruff/src/rules/flake8_slots/rules/mod.rs

@@ -0,0 +1,10 @@
+pub(crate) use no_slots_in_namedtuple_subclass::{
+    no_slots_in_namedtuple_subclass, NoSlotsInNamedtupleSubclass,
+};
+pub(crate) use no_slots_in_str_subclass::{no_slots_in_str_subclass, NoSlotsInStrSubclass};
+pub(crate) use no_slots_in_tuple_subclass::{no_slots_in_tuple_subclass, NoSlotsInTupleSubclass};
+
+mod helpers;
+mod no_slots_in_namedtuple_subclass;
+mod no_slots_in_str_subclass;
+mod no_slots_in_tuple_subclass;

crates/ruff/src/rules/flake8_slots/rules/no_slots_in_namedtuple_subclass.rs

@@ -0,0 +1,84 @@
+use rustpython_parser::ast;
+use rustpython_parser::ast::{Expr, StmtClassDef};
+
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::helpers::identifier_range;
+use ruff_python_ast::prelude::Stmt;
+
+use crate::checkers::ast::Checker;
+use crate::rules::flake8_slots::rules::helpers::has_slots;
+
+/// ## What it does
+/// Checks for subclasses of `collections.namedtuple` that lack a `__slots__`
+/// definition.
+///
+/// ## Why is this bad?
+/// In Python, the `__slots__` attribute allows you to explicitly define the
+/// attributes (instance variables) that a class can have. By default, Python
+/// uses a dictionary to store an object's attributes, which incurs some memory
+/// overhead. However, when `__slots__` is defined, Python uses a more compact
+/// internal structure to store the object's attributes, resulting in memory
+/// savings.
+///
+/// Subclasses of `namedtuple` inherit all the attributes and methods of the
+/// built-in `namedtuple` class. Since tuples are typically immutable, they
+/// don't require additional attributes beyond what the `namedtuple` class
+/// provides. Defining `__slots__` for subclasses of `namedtuple` prevents the
+/// creation of a dictionary for each instance, reducing memory consumption.
+///
+/// ## Example
+/// ```python
+/// from collections import namedtuple
+///
+///
+/// class Foo(namedtuple("foo", ["str", "int"])):
+///     pass
+/// ```
+///
+/// Use instead:
+/// ```python
+/// from collections import namedtuple
+///
+///
+/// class Foo(namedtuple("foo", ["str", "int"])):
+///     __slots__ = ()
+/// ```
+///
+/// ## References
+/// - [Python documentation: `__slots__`](https://docs.python.org/3.7/reference/datamodel.html#slots)
+#[violation]
+pub struct NoSlotsInNamedtupleSubclass;
+
+impl Violation for NoSlotsInNamedtupleSubclass {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Subclasses of `collections.namedtuple()` should define `__slots__`")
+    }
+}
+
+/// SLOT002
+pub(crate) fn no_slots_in_namedtuple_subclass(
+    checker: &mut Checker,
+    stmt: &Stmt,
+    class: &StmtClassDef,
+) {
+    if class.bases.iter().any(|base| {
+        let Expr::Call(ast::ExprCall { func, .. }) = base else {
+            return false;
+        };
+        checker
+            .semantic_model()
+            .resolve_call_path(func)
+            .map_or(false, |call_path| {
+                matches!(call_path.as_slice(), ["collections", "namedtuple"])
+            })
+    }) {
+        if !has_slots(&class.body) {
+            checker.diagnostics.push(Diagnostic::new(
+                NoSlotsInNamedtupleSubclass,
+                identifier_range(stmt, checker.locator),
+            ));
+        }
+    }
+}

crates/ruff/src/rules/flake8_slots/rules/no_slots_in_str_subclass.rs

@@ -0,0 +1,68 @@
+use rustpython_parser::ast::{Stmt, StmtClassDef};
+
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::helpers::identifier_range;
+
+use crate::checkers::ast::Checker;
+use crate::rules::flake8_slots::rules::helpers::has_slots;
+
+/// ## What it does
+/// Checks for subclasses of `str` that lack a `__slots__` definition.
+///
+/// ## Why is this bad?
+/// In Python, the `__slots__` attribute allows you to explicitly define the
+/// attributes (instance variables) that a class can have. By default, Python
+/// uses a dictionary to store an object's attributes, which incurs some memory
+/// overhead. However, when `__slots__` is defined, Python uses a more compact
+/// internal structure to store the object's attributes, resulting in memory
+/// savings.
+///
+/// Subclasses of `str` inherit all the attributes and methods of the built-in
+/// `str` class. Since strings are typically immutable, they don't require
+/// additional attributes beyond what the `str` class provides. Defining
+/// `__slots__` for subclasses of `str` prevents the creation of a dictionary
+/// for each instance, reducing memory consumption.
+///
+/// ## Example
+/// ```python
+/// class Foo(str):
+///     pass
+/// ```
+///
+/// Use instead:
+/// ```python
+/// class Foo(str):
+///     __slots__ = ()
+/// ```
+///
+/// ## References
+/// - [Python documentation: `__slots__`](https://docs.python.org/3.7/reference/datamodel.html#slots)
+#[violation]
+pub struct NoSlotsInStrSubclass;
+
+impl Violation for NoSlotsInStrSubclass {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Subclasses of `str` should define `__slots__`")
+    }
+}
+
+/// SLOT000
+pub(crate) fn no_slots_in_str_subclass(checker: &mut Checker, stmt: &Stmt, class: &StmtClassDef) {
+    if class.bases.iter().any(|base| {
+        checker
+            .semantic_model()
+            .resolve_call_path(base)
+            .map_or(false, |call_path| {
+                matches!(call_path.as_slice(), ["" | "builtins", "str"])
+            })
+    }) {
+        if !has_slots(&class.body) {
+            checker.diagnostics.push(Diagnostic::new(
+                NoSlotsInStrSubclass,
+                identifier_range(stmt, checker.locator),
+            ));
+        }
+    }
+}