[flake8-comprehension] Strip parentheses around generators in C400

crates/ruff_linter/resources/test/fixtures/flake8_comprehensions/C400.py

@@ -11,6 +11,11 @@
     x for x in range(3)
 )
 
+# Strip parentheses from inner generators.
+list((2 * x for x in range(3)))
+list(((2 * x for x in range(3))))
+list((((2 * x for x in range(3)))))
+
 # Not built-in list.
 def list(*args, **kwargs):
     return None

crates/ruff_linter/src/rules/flake8_comprehensions/rules/unnecessary_generator_list.rs

@@ -2,6 +2,7 @@ use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast as ast;
 use ruff_python_ast::comparable::ComparableExpr;
+use ruff_python_ast::parenthesize::parenthesized_range;
 use ruff_python_ast::ExprGenerator;
 use ruff_text_size::{Ranged, TextSize};
 
@@ -26,12 +27,14 @@ use super::helpers;
 /// ```python
 /// list(f(x) for x in foo)
 /// list(x for x in foo)
+/// list((x for x in foo))
 /// ```
 ///
 /// Use instead:
 /// ```python
 /// [f(x) for x in foo]
 /// list(foo)
+/// list(foo)
 /// ```
 ///
 /// ## Fix safety
@@ -76,7 +79,10 @@ pub(crate) fn unnecessary_generator_list(checker: &mut Checker, call: &ast::Expr
     }
 
     let Some(ExprGenerator {
-        elt, generators, ..
+        elt,
+        generators,
+        parenthesized,
+        ..
     }) = argument.as_generator_expr()
     else {
         return;
@@ -125,7 +131,28 @@ pub(crate) fn unnecessary_generator_list(checker: &mut Checker, call: &ast::Expr
             call.end(),
         );
 
-        Fix::unsafe_edits(call_start, [call_end])
+        // Remove the inner parentheses, if the expression is a generator. The easiest way to do
+        // this reliably is to use the printer.
+        if *parenthesized {
+            // The generator's range will include the innermost parentheses, but it could be
+            // surrounded by additional parentheses.
+            let range = parenthesized_range(
+                argument.into(),
+                (&call.arguments).into(),
+                checker.indexer().comment_ranges(),
+                checker.locator().contents(),
+            )
+            .unwrap_or(argument.range());
+
+            // The generator always parenthesizes the expression; trim the parentheses.
+            let generator = checker.generator().expr(argument);
+            let generator = generator[1..generator.len() - 1].to_string();
+
+            let replacement = Edit::range_replacement(generator, range);
+            Fix::unsafe_edits(call_start, [call_end, replacement])
+        } else {
+            Fix::unsafe_edits(call_start, [call_end])
+        }
     });
 
     checker.diagnostics.push(diagnostic);

crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__C400_C400.py.snap

@@ -73,7 +73,7 @@ C400.py:10:5: C400 [*] Unnecessary generator (rewrite using `list()`)
 12 | | )
    | |_^ C400
 13 |   
-14 |   # Not built-in list.
+14 |   # Strip parentheses from inner generators.
    |
    = help: Rewrite using `list()`
 
@@ -86,5 +86,66 @@ C400.py:10:5: C400 [*] Unnecessary generator (rewrite using `list()`)
 12    |-)
    10 |+x = list(range(3))
 13 11 | 
-14 12 | # Not built-in list.
-15 13 | def list(*args, **kwargs):
+14 12 | # Strip parentheses from inner generators.
+15 13 | list((2 * x for x in range(3)))
+
+C400.py:15:1: C400 [*] Unnecessary generator (rewrite as a `list` comprehension)
+   |
+14 | # Strip parentheses from inner generators.
+15 | list((2 * x for x in range(3)))
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C400
+16 | list(((2 * x for x in range(3))))
+17 | list((((2 * x for x in range(3)))))
+   |
+   = help: Rewrite as a `list` comprehension
+
+ℹ Unsafe fix
+12 12 | )
+13 13 | 
+14 14 | # Strip parentheses from inner generators.
+15    |-list((2 * x for x in range(3)))
+   15 |+[2 * x for x in range(3)]
+16 16 | list(((2 * x for x in range(3))))
+17 17 | list((((2 * x for x in range(3)))))
+18 18 | 
+
+C400.py:16:1: C400 [*] Unnecessary generator (rewrite as a `list` comprehension)
+   |
+14 | # Strip parentheses from inner generators.
+15 | list((2 * x for x in range(3)))
+16 | list(((2 * x for x in range(3))))
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C400
+17 | list((((2 * x for x in range(3)))))
+   |
+   = help: Rewrite as a `list` comprehension
+
+ℹ Unsafe fix
+13 13 | 
+14 14 | # Strip parentheses from inner generators.
+15 15 | list((2 * x for x in range(3)))
+16    |-list(((2 * x for x in range(3))))
+   16 |+[2 * x for x in range(3)]
+17 17 | list((((2 * x for x in range(3)))))
+18 18 | 
+19 19 | # Not built-in list.
+
+C400.py:17:1: C400 [*] Unnecessary generator (rewrite as a `list` comprehension)
+   |
+15 | list((2 * x for x in range(3)))
+16 | list(((2 * x for x in range(3))))
+17 | list((((2 * x for x in range(3)))))
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C400
+18 | 
+19 | # Not built-in list.
+   |
+   = help: Rewrite as a `list` comprehension
+
+ℹ Unsafe fix
+14 14 | # Strip parentheses from inner generators.
+15 15 | list((2 * x for x in range(3)))
+16 16 | list(((2 * x for x in range(3))))
+17    |-list((((2 * x for x in range(3)))))
+   17 |+[2 * x for x in range(3)]
+18 18 | 
+19 19 | # Not built-in list.
+20 20 | def list(*args, **kwargs):