[ruff] Implement redundant-bool-literal (RUF038)

crates/ruff_linter/resources/test/fixtures/ruff/RUF038.py

@@ -0,0 +1,33 @@
+from typing import Literal
+
+
+def func1(arg1: Literal[True, False]): 
+    ...
+
+
+def func2(arg1: Literal[True, False, True]): 
+    ...
+
+
+def func3() -> Literal[True, False]: 
+    ...
+
+
+def func4(arg1: Literal[True, False] | bool): 
+    ...
+
+
+def func5(arg1: Literal[False, True]):
+    ...
+
+
+def func6(arg1: Literal[True, False, "hello", "world"]):
+    ...
+
+# ok
+def good_func1(arg1: bool): 
+    ...
+
+
+def good_func2(arg1: Literal[True]):
+    ...

crates/ruff_linter/resources/test/fixtures/ruff/RUF038.pyi

@@ -0,0 +1,20 @@
+from typing import Literal
+
+
+def func1(arg1: Literal[True, False]): ...
+
+def func2(arg1: Literal[True, False, True]): ...
+
+def func3() -> Literal[True, False]: ...
+
+def func4(arg1: Literal[True, False] | bool): ...
+
+def func5(arg1: Literal[False, True]): ...
+
+def func6(arg1: Literal[True, False, "hello", "world"]): ...
+
+# ok
+def good_func1(arg1: bool): ...
+
+def good_func2(arg1: Literal[True]): ...
+

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

@@ -100,9 +100,14 @@ pub(crate) fn expression(expr: &Expr, checker: &mut Checker) {
             }
 
             // Ex) Literal[...]
-            if checker.enabled(Rule::DuplicateLiteralMember) {
+            if checker.any_enabled(&[Rule::DuplicateLiteralMember, Rule::RedundantBoolLiteral]) {
                 if !checker.semantic.in_nested_literal() {
-                    flake8_pyi::rules::duplicate_literal_member(checker, expr);
+                    if checker.enabled(Rule::DuplicateLiteralMember) {
+                        flake8_pyi::rules::duplicate_literal_member(checker, expr);
+                    }
+                    if checker.enabled(Rule::RedundantBoolLiteral) {
+                        ruff::rules::redundant_bool_literal(checker, expr);
+                    }
                 }
             }
 

crates/ruff_linter/src/codes.rs

@@ -967,6 +967,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Ruff, "033") => (RuleGroup::Preview, rules::ruff::rules::PostInitDefault),
         (Ruff, "034") => (RuleGroup::Preview, rules::ruff::rules::UselessIfElse),
         (Ruff, "035") => (RuleGroup::Preview, rules::ruff::rules::UnsafeMarkupUse),
+        (Ruff, "038") => (RuleGroup::Preview, rules::ruff::rules::RedundantBoolLiteral),
         (Ruff, "100") => (RuleGroup::Stable, rules::ruff::rules::UnusedNOQA),
         (Ruff, "101") => (RuleGroup::Stable, rules::ruff::rules::RedirectedNOQA),
 

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

@@ -62,6 +62,8 @@ mod tests {
     #[test_case(Rule::UselessIfElse, Path::new("RUF034.py"))]
     #[test_case(Rule::RedirectedNOQA, Path::new("RUF101.py"))]
     #[test_case(Rule::PostInitDefault, Path::new("RUF033.py"))]
+    #[test_case(Rule::RedundantBoolLiteral, Path::new("RUF038.py"))]
+    #[test_case(Rule::RedundantBoolLiteral, Path::new("RUF038.pyi"))]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());
         let diagnostics = test_path(

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

@@ -21,6 +21,7 @@ pub(crate) use parenthesize_logical_operators::*;
 pub(crate) use post_init_default::*;
 pub(crate) use quadratic_list_summation::*;
 pub(crate) use redirected_noqa::*;
+pub(crate) use redundant_bool_literal::*;
 pub(crate) use sort_dunder_all::*;
 pub(crate) use sort_dunder_slots::*;
 pub(crate) use static_key_dict_comprehension::*;
@@ -59,6 +60,7 @@ mod parenthesize_logical_operators;
 mod post_init_default;
 mod quadratic_list_summation;
 mod redirected_noqa;
+mod redundant_bool_literal;
 mod sequence_sorting;
 mod sort_dunder_all;
 mod sort_dunder_slots;

crates/ruff_linter/src/rules/ruff/rules/redundant_bool_literal.rs

@@ -0,0 +1,124 @@
+use ruff_diagnostics::{Diagnostic, Edit, Fix, FixAvailability, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::Expr;
+use ruff_python_semantic::analyze::typing::traverse_literal;
+use ruff_text_size::Ranged;
+
+use bitflags::bitflags;
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for `Literal[True, False]` type annotations.
+///
+/// ## Why is this bad?
+/// The `bool` type has exactly two constant instances: `True` and `False`. Writing
+/// `Literal[True, False]` in the context of type annotations could be replaced by a
+/// bare `bool` annotations. Static type checkers such as [mypy] treat them as
+/// equivalent.
+///
+/// ## Example
+/// ```python
+/// Literal[True, False]
+/// Literal[True, False, "hello", "world"]
+/// ```
+///
+/// Use instead:
+/// ```python
+/// bool
+/// Literal["hello", "world"] | bool
+/// ```
+///
+/// ## Fix safety
+/// The fix for this rule is marked as unsafe:
+///
+/// - The type annotation might be intentional when the type checker used does not
+/// treat `bool` as equivalent when overloading boolean arguments with `Literal[True]`
+/// and `Literal[False]`, e.g. see [#14764] and [#5421].
+/// - `bool` is not strictly equivalent to `Literal[True, False]`, as `bool` is
+/// a subclass of `int`, and this rule might not apply if the type annotations are used
+/// in a numerical context.
+/// - The `Literal` might contain comments.
+///
+/// ## References
+/// - [Typing documentation: Legal parameters for `Literal` at type check time](https://typing.readthedocs.io/en/latest/spec/literal.html#legal-parameters-for-literal-at-type-check-time)
+/// - [Python documentation: Boolean type - `bool`](https://docs.python.org/3/library/stdtypes.html#boolean-type-bool)
+///
+/// [mypy](https://github.com/python/mypy/blob/master/mypy/typeops.py#L985)
+/// [#14764](https://github.com/python/mypy/issues/14764)
+/// [#5421](https://github.com/microsoft/pyright/issues/5421)
+#[violation]
+pub struct RedundantBoolLiteral {
+    seen_others: bool,
+}
+
+impl Violation for RedundantBoolLiteral {
+    const FIX_AVAILABILITY: FixAvailability = FixAvailability::Sometimes;
+
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        if self.seen_others {
+            "`Literal[True, False, ...]` can be replaced with `Literal[...] | bool`".to_string()
+        } else {
+            "`Literal[True, False]` can be replaced with a bare `bool`".to_string()
+        }
+    }
+
+    fn fix_title(&self) -> Option<String> {
+        Some("Replace with `bool`".to_string())
+    }
+}
+
+/// RUF038
+pub(crate) fn redundant_bool_literal<'a>(checker: &mut Checker, literal_expr: &'a Expr) {
+    if !checker.semantic().seen_typing() {
+        return;
+    }
+
+    let mut seen_expr = BooleanLiteral::empty();
+
+    let mut find_bools = |expr: &'a Expr, _parent: &'a Expr| {
+        let expr_type = match expr {
+            Expr::BooleanLiteral(boolean_expr) => {
+                if boolean_expr.value {
+                    BooleanLiteral::TRUE
+                } else {
+                    BooleanLiteral::FALSE
+                }
+            }
+            _ => BooleanLiteral::OTHER,
+        };
+        seen_expr.insert(expr_type);
+    };
+
+    traverse_literal(&mut find_bools, checker.semantic(), literal_expr);
+
+    if !seen_expr.contains(BooleanLiteral::TRUE | BooleanLiteral::FALSE) {
+        return;
+    }
+
+    let seen_others = seen_expr.contains(BooleanLiteral::OTHER);
+
+    let mut diagnostic =
+        Diagnostic::new(RedundantBoolLiteral { seen_others }, literal_expr.range());
+
+    // Provide a [`Fix`] when the complete `Literal` can be replaced. Applying the fix
+    // can leave an unused import to be fixed by the `unused-import` rule.
+    if !seen_others {
+        diagnostic.set_fix(Fix::unsafe_edit(Edit::range_replacement(
+            "bool".to_string(),
+            literal_expr.range(),
+        )));
+    }
+
+    checker.diagnostics.push(diagnostic);
+}
+
+bitflags! {
+    #[derive(Default, Debug)]
+    struct BooleanLiteral: u8 {
+        const TRUE = 1 << 0;
+        const FALSE = 1 << 1;
+        const OTHER = 1 << 2;
+    }
+}

crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF038_RUF038.py.snap

@@ -0,0 +1,100 @@
+---
+source: crates/ruff_linter/src/rules/ruff/mod.rs
+---
+RUF038.py:4:17: RUF038 [*] `Literal[True, False]` can be replaced with a bare `bool`
+  |
+4 | def func1(arg1: Literal[True, False]): 
+  |                 ^^^^^^^^^^^^^^^^^^^^ RUF038
+5 |     ...
+  |
+  = help: Replace with `bool`
+
+ℹ Unsafe fix
+1 1 | from typing import Literal
+2 2 | 
+3 3 | 
+4   |-def func1(arg1: Literal[True, False]): 
+  4 |+def func1(arg1: bool): 
+5 5 |     ...
+6 6 | 
+7 7 | 
+
+RUF038.py:8:17: RUF038 [*] `Literal[True, False]` can be replaced with a bare `bool`
+  |
+8 | def func2(arg1: Literal[True, False, True]): 
+  |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ RUF038
+9 |     ...
+  |
+  = help: Replace with `bool`
+
+ℹ Unsafe fix
+5 5 |     ...
+6 6 | 
+7 7 | 
+8   |-def func2(arg1: Literal[True, False, True]): 
+  8 |+def func2(arg1: bool): 
+9 9 |     ...
+10 10 | 
+11 11 | 
+
+RUF038.py:12:16: RUF038 [*] `Literal[True, False]` can be replaced with a bare `bool`
+   |
+12 | def func3() -> Literal[True, False]: 
+   |                ^^^^^^^^^^^^^^^^^^^^ RUF038
+13 |     ...
+   |
+   = help: Replace with `bool`
+
+ℹ Unsafe fix
+9  9  |     ...
+10 10 | 
+11 11 | 
+12    |-def func3() -> Literal[True, False]: 
+   12 |+def func3() -> bool: 
+13 13 |     ...
+14 14 | 
+15 15 | 
+
+RUF038.py:16:17: RUF038 [*] `Literal[True, False]` can be replaced with a bare `bool`
+   |
+16 | def func4(arg1: Literal[True, False] | bool): 
+   |                 ^^^^^^^^^^^^^^^^^^^^ RUF038
+17 |     ...
+   |
+   = help: Replace with `bool`
+
+ℹ Unsafe fix
+13 13 |     ...
+14 14 | 
+15 15 | 
+16    |-def func4(arg1: Literal[True, False] | bool): 
+   16 |+def func4(arg1: bool | bool): 
+17 17 |     ...
+18 18 | 
+19 19 | 
+
+RUF038.py:20:17: RUF038 [*] `Literal[True, False]` can be replaced with a bare `bool`
+   |
+20 | def func5(arg1: Literal[False, True]):
+   |                 ^^^^^^^^^^^^^^^^^^^^ RUF038
+21 |     ...
+   |
+   = help: Replace with `bool`
+
+ℹ Unsafe fix
+17 17 |     ...
+18 18 | 
+19 19 | 
+20    |-def func5(arg1: Literal[False, True]):
+   20 |+def func5(arg1: bool):
+21 21 |     ...
+22 22 | 
+23 23 | 
+
+RUF038.py:24:17: RUF038 `Literal[True, False, ...]` can be replaced with `Literal[...] | bool`
+   |
+24 | def func6(arg1: Literal[True, False, "hello", "world"]):
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ RUF038
+25 |     ...
+   |
+   = help: Replace with `bool`