Rewrite `not not a` as `bool(a)` in boolean contexts (#4294)

crates/ruff/resources/test/fixtures/flake8_simplify/SIM208.py

@@ -12,3 +12,10 @@ if not a == b:  # OK
 
 if not a != b:  # OK
     pass
+
+a = not not b  # SIM208
+
+f(not not a)  # SIM208
+
+if 1 + (not (not a)):  # SIM208
+    pass

crates/ruff/resources/test/fixtures/flake8_simplify/SIM210.py

@@ -6,6 +6,7 @@ a = True if b + c else False  # SIM210
 
 a = False if b else True  # OK
 
+
 def f():
     # OK
     def bool():

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

@@ -7,7 +7,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 use rustpython_common::cformat::{CFormatError, CFormatErrorType};
 use rustpython_parser::ast::{
     Arg, Arguments, Comprehension, Constant, Excepthandler, ExcepthandlerKind, Expr, ExprContext,
-    ExprKind, KeywordData, Located, Operator, Pattern, PatternKind, Stmt, StmtKind, Suite,
+    ExprKind, KeywordData, Located, Operator, Pattern, PatternKind, Stmt, StmtKind, Suite, Unaryop,
 };
 
 use ruff_diagnostics::{Diagnostic, Fix};
@@ -2299,7 +2299,16 @@ where
         let prev_in_type_definition = self.ctx.in_type_definition;
         let prev_in_boolean_test = self.ctx.in_boolean_test;
 
-        if !matches!(expr.node, ExprKind::BoolOp { .. }) {
+        // If we're in a boolean test (e.g., the `test` of a `StmtKind::If`), but now within a
+        // subexpression (e.g., `a` in `f(a)`), then we're no longer in a boolean test.
+        if !matches!(
+            expr.node,
+            ExprKind::BoolOp { .. }
+                | ExprKind::UnaryOp {
+                    op: Unaryop::Not,
+                    ..
+                }
+        ) {
             self.ctx.in_boolean_test = false;
         }
 

crates/ruff/src/rules/flake8_simplify/rules/ast_unary_op.rs

@@ -1,4 +1,4 @@
-use rustpython_parser::ast::{Cmpop, Expr, ExprKind, Stmt, StmtKind, Unaryop};
+use rustpython_parser::ast::{Cmpop, Expr, ExprContext, ExprKind, Stmt, StmtKind, Unaryop};
 
 use ruff_diagnostics::{AlwaysAutofixableViolation, Diagnostic, Edit, Fix};
 use ruff_macros::{derive_message_formats, violation};
@@ -191,10 +191,27 @@ pub fn double_negation(checker: &mut Checker, expr: &Expr, op: &Unaryop, operand
         expr.range(),
     );
     if checker.patch(diagnostic.kind.rule()) {
-        diagnostic.set_fix(Fix::unspecified(Edit::range_replacement(
-            unparse_expr(operand, checker.stylist),
-            expr.range(),
-        )));
+        if checker.ctx.in_boolean_test {
+            diagnostic.set_fix(Fix::unspecified(Edit::range_replacement(
+                unparse_expr(operand, checker.stylist),
+                expr.range(),
+            )));
+        } else if checker.ctx.is_builtin("bool") {
+            diagnostic.set_fix(Fix::unspecified(Edit::range_replacement(
+                unparse_expr(
+                    &create_expr(ExprKind::Call {
+                        func: Box::new(create_expr(ExprKind::Name {
+                            id: "bool".to_string(),
+                            ctx: ExprContext::Load,
+                        })),
+                        args: vec![*operand.clone()],
+                        keywords: vec![],
+                    }),
+                    checker.stylist,
+                ),
+                expr.range(),
+            )));
+        };
     }
     checker.diagnostics.push(diagnostic);
 }

crates/ruff/src/rules/flake8_simplify/snapshots/ruff__rules__flake8_simplify__tests__SIM208_SIM208.py.snap

@@ -36,4 +36,64 @@ SIM208.py:4:4: SIM208 [*] Use `a == b` instead of `not (not a == b)`
 6 6 | 
 7 7 | if not a:  # OK
 
+SIM208.py:16:5: SIM208 [*] Use `b` instead of `not (not b)`
+   |
+16 |     pass
+17 | 
+18 | a = not not b  # SIM208
+   |     ^^^^^^^^^ SIM208
+19 | 
+20 | f(not not a)  # SIM208
+   |
+   = help: Replace with `b`
+
+ℹ Suggested fix
+13 13 | if not a != b:  # OK
+14 14 |     pass
+15 15 | 
+16    |-a = not not b  # SIM208
+   16 |+a = bool(b)  # SIM208
+17 17 | 
+18 18 | f(not not a)  # SIM208
+19 19 | 
+
+SIM208.py:18:3: SIM208 [*] Use `a` instead of `not (not a)`
+   |
+18 | a = not not b  # SIM208
+19 | 
+20 | f(not not a)  # SIM208
+   |   ^^^^^^^^^ SIM208
+21 | 
+22 | if 1 + (not (not a)):  # SIM208
+   |
+   = help: Replace with `a`
+
+ℹ Suggested fix
+15 15 | 
+16 16 | a = not not b  # SIM208
+17 17 | 
+18    |-f(not not a)  # SIM208
+   18 |+f(bool(a))  # SIM208
+19 19 | 
+20 20 | if 1 + (not (not a)):  # SIM208
+21 21 |     pass
+
+SIM208.py:20:9: SIM208 [*] Use `a` instead of `not (not a)`
+   |
+20 | f(not not a)  # SIM208
+21 | 
+22 | if 1 + (not (not a)):  # SIM208
+   |         ^^^^^^^^^^^ SIM208
+23 |     pass
+   |
+   = help: Replace with `a`
+
+ℹ Suggested fix
+17 17 | 
+18 18 | f(not not a)  # SIM208
+19 19 | 
+20    |-if 1 + (not (not a)):  # SIM208
+   20 |+if 1 + (bool(a)):  # SIM208
+21 21 |     pass
+
 

crates/ruff/src/rules/flake8_simplify/snapshots/ruff__rules__flake8_simplify__tests__SIM210_SIM210.py.snap

@@ -58,11 +58,11 @@ SIM210.py:5:5: SIM210 [*] Use `bool(b + c)` instead of `True if b + c else False
 7 7 | a = False if b else True  # OK
 8 8 | 
 
-SIM210.py:14:9: SIM210 [*] Use `bool(b)` instead of `True if b else False`
+SIM210.py:15:9: SIM210 [*] Use `bool(b)` instead of `True if b else False`
    |
-14 |         return False
-15 | 
-16 |     a = True if b else False
+15 |         return False
+16 | 
+17 |     a = True if b else False
    |         ^^^^^^^^^^^^^^^^^^^^ SIM210
    |
    = help: Replace with `not b