mirror of https://github.com/astral-sh/ruff
[`flake8_comprehensions`] Handled special case for `C400` which also matches `C416` (#10419)
## Summary Short-circuit implementation mentioned in #10403. I implemented this by extending C400: - Made `UnnecessaryGeneratorList` have information of whether the the short-circuiting occurred (to put diagnostic) - Add additional check for whether in `unnecessary_generator_list` function. Please give me suggestions if you think this isn't the best way to handle this :) ## Test Plan Extended `C400.py` a little, and written the cases where: - Code could be converted to one single conversion to `list` e.g. `list(x for x in range(3))` -> `list(range(3))` - Code couldn't be converted to one single conversion to `list` e.g. `list(2 * x for x in range(3))` -> `[2 * x for x in range(3)]` - `list` function is not built-in, and should not modify the code in any way.
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hikaru-kajita
GitHub
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commit
7e652e8fcb
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@ -1,11 +1,20 @@
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# Cannot combine with C416. Should use list comprehension here.
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even_nums = list(2 * x for x in range(3))
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odd_nums = list(
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2 * x + 1 for x in range(3)
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)
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# Short-circuit case, combine with C416 and should produce x = list(range(3))
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x = list(x for x in range(3))
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x = list(
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x for x in range(3)
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)
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# Not built-in list.
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def list(*args, **kwargs):
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return None
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list(2 * x for x in range(3))
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list(x for x in range(3))
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@ -1,6 +1,8 @@
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use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
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use ruff_macros::{derive_message_formats, violation};
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use ruff_python_ast as ast;
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use ruff_python_ast::comparable::ComparableExpr;
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use ruff_python_ast::ExprGenerator;
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use ruff_text_size::{Ranged, TextSize};
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use crate::checkers::ast::Checker;
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@ -9,38 +11,54 @@ use super::helpers;
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/// ## What it does
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/// Checks for unnecessary generators that can be rewritten as `list`
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/// comprehensions.
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/// comprehensions (or with `list` directly).
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///
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/// ## Why is this bad?
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/// It is unnecessary to use `list` around a generator expression, since
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/// there are equivalent comprehensions for these types. Using a
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/// comprehension is clearer and more idiomatic.
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///
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/// Further, if the comprehension can be removed entirely, as in the case of
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/// `list(x for x in foo)`, it's better to use `list(foo)` directly, since it's
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/// even more direct.
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///
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/// ## Examples
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/// ```python
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/// list(f(x) for x in foo)
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/// list(x for x in foo)
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/// ```
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///
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/// Use instead:
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/// ```python
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/// [f(x) for x in foo]
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/// list(foo)
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/// ```
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///
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/// ## Fix safety
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/// This rule's fix is marked as unsafe, as it may occasionally drop comments
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/// when rewriting the call. In most cases, though, comments will be preserved.
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#[violation]
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pub struct UnnecessaryGeneratorList;
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pub struct UnnecessaryGeneratorList {
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short_circuit: bool,
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}
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impl AlwaysFixableViolation for UnnecessaryGeneratorList {
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#[derive_message_formats]
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fn message(&self) -> String {
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if self.short_circuit {
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format!("Unnecessary generator (rewrite using `list()`")
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} else {
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format!("Unnecessary generator (rewrite as a `list` comprehension)")
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}
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}
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fn fix_title(&self) -> String {
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if self.short_circuit {
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"Rewrite using `list()`".to_string()
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} else {
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"Rewrite as a `list` comprehension".to_string()
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}
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}
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}
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/// C400 (`list(generator)`)
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@ -56,10 +74,42 @@ pub(crate) fn unnecessary_generator_list(checker: &mut Checker, call: &ast::Expr
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if !checker.semantic().is_builtin("list") {
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return;
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}
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if argument.is_generator_expr() {
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let mut diagnostic = Diagnostic::new(UnnecessaryGeneratorList, call.range());
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// Convert `list(x for x in y)` to `[x for x in y]`.
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let Some(ExprGenerator {
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elt, generators, ..
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}) = argument.as_generator_expr()
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else {
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return;
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};
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// Short-circuit: given `list(x for x in y)`, generate `list(y)` (in lieu of `[x for x in y]`).
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if let [generator] = generators.as_slice() {
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if generator.ifs.is_empty() && !generator.is_async {
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if ComparableExpr::from(elt) == ComparableExpr::from(&generator.target) {
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let mut diagnostic = Diagnostic::new(
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UnnecessaryGeneratorList {
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short_circuit: true,
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},
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call.range(),
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);
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let iterator = format!("list({})", checker.locator().slice(generator.iter.range()));
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diagnostic.set_fix(Fix::unsafe_edit(Edit::range_replacement(
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iterator,
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call.range(),
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)));
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checker.diagnostics.push(diagnostic);
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return;
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}
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}
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}
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// Convert `list(f(x) for x in y)` to `[f(x) for x in y]`.
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let mut diagnostic = Diagnostic::new(
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UnnecessaryGeneratorList {
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short_circuit: false,
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},
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call.range(),
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);
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diagnostic.set_fix({
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// Replace `list(` with `[`.
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let call_start = Edit::replacement(
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@ -79,5 +129,4 @@ pub(crate) fn unnecessary_generator_list(checker: &mut Checker, call: &ast::Expr
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});
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checker.diagnostics.push(diagnostic);
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}
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}
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@ -1,42 +1,90 @@
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---
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source: crates/ruff_linter/src/rules/flake8_comprehensions/mod.rs
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---
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C400.py:1:5: C400 [*] Unnecessary generator (rewrite as a `list` comprehension)
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C400.py:2:13: C400 [*] Unnecessary generator (rewrite as a `list` comprehension)
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1 | x = list(x for x in range(3))
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| ^^^^^^^^^^^^^^^^^^^^^^^^^ C400
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2 | x = list(
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3 | x for x in range(3)
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1 | # Cannot combine with C416. Should use list comprehension here.
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2 | even_nums = list(2 * x for x in range(3))
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ C400
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3 | odd_nums = list(
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4 | 2 * x + 1 for x in range(3)
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= help: Rewrite as a `list` comprehension
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ℹ Unsafe fix
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1 |-x = list(x for x in range(3))
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1 |+x = [x for x in range(3)]
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2 2 | x = list(
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3 3 | x for x in range(3)
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4 4 | )
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1 1 | # Cannot combine with C416. Should use list comprehension here.
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2 |-even_nums = list(2 * x for x in range(3))
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2 |+even_nums = [2 * x for x in range(3)]
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3 3 | odd_nums = list(
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4 4 | 2 * x + 1 for x in range(3)
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5 5 | )
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C400.py:2:5: C400 [*] Unnecessary generator (rewrite as a `list` comprehension)
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C400.py:3:12: C400 [*] Unnecessary generator (rewrite as a `list` comprehension)
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1 | x = list(x for x in range(3))
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2 | x = list(
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| _____^
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3 | | x for x in range(3)
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4 | | )
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1 | # Cannot combine with C416. Should use list comprehension here.
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2 | even_nums = list(2 * x for x in range(3))
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3 | odd_nums = list(
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| ____________^
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4 | | 2 * x + 1 for x in range(3)
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5 | | )
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| |_^ C400
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= help: Rewrite as a `list` comprehension
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ℹ Unsafe fix
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1 1 | x = list(x for x in range(3))
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2 |-x = list(
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2 |+x = [
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3 3 | x for x in range(3)
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4 |-)
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4 |+]
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5 5 |
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1 1 | # Cannot combine with C416. Should use list comprehension here.
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2 2 | even_nums = list(2 * x for x in range(3))
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3 |-odd_nums = list(
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3 |+odd_nums = [
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4 4 | 2 * x + 1 for x in range(3)
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5 |-)
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5 |+]
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6 6 |
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7 7 | def list(*args, **kwargs):
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7 7 |
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8 8 | # Short-circuit case, combine with C416 and should produce x = list(range(3))
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C400.py:9:5: C400 [*] Unnecessary generator (rewrite using `list()`
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8 | # Short-circuit case, combine with C416 and should produce x = list(range(3))
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9 | x = list(x for x in range(3))
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| ^^^^^^^^^^^^^^^^^^^^^^^^^ C400
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10 | x = list(
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11 | x for x in range(3)
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= help: Rewrite using `list()`
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ℹ Unsafe fix
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6 6 |
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7 7 |
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8 8 | # Short-circuit case, combine with C416 and should produce x = list(range(3))
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9 |-x = list(x for x in range(3))
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9 |+x = list(range(3))
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10 10 | x = list(
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11 11 | x for x in range(3)
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12 12 | )
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C400.py:10:5: C400 [*] Unnecessary generator (rewrite using `list()`
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8 | # Short-circuit case, combine with C416 and should produce x = list(range(3))
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9 | x = list(x for x in range(3))
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10 | x = list(
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| _____^
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11 | | x for x in range(3)
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12 | | )
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| |_^ C400
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13 |
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14 | # Not built-in list.
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= help: Rewrite using `list()`
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ℹ Unsafe fix
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7 7 |
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8 8 | # Short-circuit case, combine with C416 and should produce x = list(range(3))
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9 9 | x = list(x for x in range(3))
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10 |-x = list(
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11 |- x for x in range(3)
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12 |-)
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10 |+x = list(range(3))
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13 11 |
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14 12 | # Not built-in list.
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15 13 | def list(*args, **kwargs):
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