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[refurb] Implement for-loop-writes (FURB122) (#10630)

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## Summary
Implement `for-loop-writes` (FURB122) lint
- https://github.com/astral-sh/ruff/issues/1348
- [original
lint](https://github.com/dosisod/refurb/blob/master/refurb/checks/builtin/writelines.py)

---------

Co-authored-by: dylwil3 <dylwil3@gmail.com>
This commit is contained in:
Aleksei Latyshev 2025-01-16 22:02:46 +01:00 • committed by GitHub
parent 2e6729d900
commit 177bf72598
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8 changed files with 363 additions and 0 deletions
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66
crates/ruff_linter/resources/test/fixtures/refurb/FURB122.py vendored Normal file
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@ -0,0 +1,66 @@
from pathlib import Path
lines = ["line 1", "line 2", "line 3"]
# Errors
with open("file", "w") as f:
for line in lines:
f.write(line)
other_line = "other line"
with Path("file").open("w") as f:
for line in lines:
f.write(other_line)
with Path("file").open("w") as f:
for line in lines:
f.write(line)
with Path("file").open("wb") as f:
for line in lines:
f.write(line.encode())
with Path("file").open("w") as f:
for line in lines:
f.write(line.upper())
with Path("file").open("w") as f:
pass
for line in lines:
f.write(line)
# Offer unsafe fix if it would delete comments
with open("file","w") as f:
for line in lines:
# a really important comment
f.write(line)
# OK
for line in lines:
Path("file").open("w").write(line)
with Path("file").open("w") as f:
for line in lines:
pass
f.write(line)
with Path("file").open("w") as f:
for line in lines:
f.write(line)
else:
pass
async def func():
with Path("file").open("w") as f:
async for line in lines: # type: ignore
f.write(line)
with Path("file").open("w") as f:
for line in lines:
f.write() # type: ignore

3
crates/ruff_linter/src/checkers/ast/analyze/statement.rs
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@ -1431,6 +1431,9 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
if checker.enabled(Rule::ForLoopSetMutations) {
refurb::rules::for_loop_set_mutations(checker, for_stmt);
}
if checker.enabled(Rule::ForLoopWrites) {
refurb::rules::for_loop_writes(checker, for_stmt);
}
}
}
Stmt::Try(ast::StmtTry {

1
crates/ruff_linter/src/codes.rs
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@ -1089,6 +1089,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
(Refurb, "113") => (RuleGroup::Preview, rules::refurb::rules::RepeatedAppend),
(Refurb, "116") => (RuleGroup::Preview, rules::refurb::rules::FStringNumberFormat),
(Refurb, "118") => (RuleGroup::Preview, rules::refurb::rules::ReimplementedOperator),
(Refurb, "122") => (RuleGroup::Preview, rules::refurb::rules::ForLoopWrites),
(Refurb, "129") => (RuleGroup::Stable, rules::refurb::rules::ReadlinesInFor),
(Refurb, "131") => (RuleGroup::Preview, rules::refurb::rules::DeleteFullSlice),
(Refurb, "132") => (RuleGroup::Preview, rules::refurb::rules::CheckAndRemoveFromSet),

1
crates/ruff_linter/src/rules/refurb/mod.rs
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@ -19,6 +19,7 @@ mod tests {
#[test_case(Rule::RepeatedAppend, Path::new("FURB113.py"))]
#[test_case(Rule::IfExpInsteadOfOrOperator, Path::new("FURB110.py"))]
#[test_case(Rule::ReimplementedOperator, Path::new("FURB118.py"))]
#[test_case(Rule::ForLoopWrites, Path::new("FURB122.py"))]
#[test_case(Rule::ReadlinesInFor, Path::new("FURB129.py"))]
#[test_case(Rule::DeleteFullSlice, Path::new("FURB131.py"))]
#[test_case(Rule::CheckAndRemoveFromSet, Path::new("FURB132.py"))]

128
crates/ruff_linter/src/rules/refurb/rules/for_loop_writes.rs Normal file
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@ -0,0 +1,128 @@
use ruff_diagnostics::{AlwaysFixableViolation, Applicability, Diagnostic, Edit, Fix};
use ruff_macros::{derive_message_formats, ViolationMetadata};
use ruff_python_ast::{Expr, Stmt, StmtFor};
use ruff_python_semantic::analyze::typing;
use ruff_text_size::Ranged;
use crate::checkers::ast::Checker;
/// ## What it does
/// Checks for the use of `IOBase.write` in a for loop.
///
/// ## Why is this bad?
/// When writing a batch of elements, it's more idiomatic to use a single method call to
/// `IOBase.writelines`, rather than write elements one by one.
///
/// ## Example
/// ```python
/// with Path("file").open("w") as f:
/// for line in lines:
/// f.write(line)
///
/// with Path("file").open("wb") as f:
/// for line in lines:
/// f.write(line.encode())
/// ```
///
/// Use instead:
/// ```python
/// with Path("file").open("w") as f:
/// f.writelines(lines)
///
/// with Path("file").open("wb") as f:
/// f.writelines(line.encode() for line in lines)
/// ```
///
/// ## References
/// - [Python documentation: `io.IOBase.writelines`](https://docs.python.org/3/library/io.html#io.IOBase.writelines)
#[derive(ViolationMetadata)]
pub(crate) struct ForLoopWrites {
name: String,
}
impl AlwaysFixableViolation for ForLoopWrites {
#[derive_message_formats]
fn message(&self) -> String {
format!("Use of `{}.write` in a for loop", self.name)
}
fn fix_title(&self) -> String {
format!("Replace with `{}.writelines`", self.name)
}
}
pub(crate) fn for_loop_writes(checker: &mut Checker, for_stmt: &StmtFor) {
if !for_stmt.orelse.is_empty() {
return;
}
let [Stmt::Expr(stmt_expr)] = for_stmt.body.as_slice() else {
return;
};
let Expr::Call(call_expr) = stmt_expr.value.as_ref() else {
return;
};
let Expr::Attribute(expr_attr) = call_expr.func.as_ref() else {
return;
};
if expr_attr.attr.as_str() != "write" {
return;
}
if !call_expr.arguments.keywords.is_empty() {
return;
}
let [write_arg] = call_expr.arguments.args.as_ref() else {
return;
};
let Expr::Name(io_object_name) = expr_attr.value.as_ref() else {
return;
};
// Determine whether `f` in `f.write()` was bound to a file object.
if !checker
.semantic()
.resolve_name(io_object_name)
.map(|id| checker.semantic().binding(id))
.is_some_and(|binding| typing::is_io_base(binding, checker.semantic()))
{
return;
}
let content = match (for_stmt.target.as_ref(), write_arg) {
(Expr::Name(for_target), Expr::Name(write_arg)) if for_target.id == write_arg.id => {
format!(
"{}.writelines({})",
checker.locator().slice(io_object_name),
checker.locator().slice(for_stmt.iter.as_ref()),
)
}
(for_target, write_arg) => {
format!(
"{}.writelines({} for {} in {})",
checker.locator().slice(io_object_name),
checker.locator().slice(write_arg),
checker.locator().slice(for_target),
checker.locator().slice(for_stmt.iter.as_ref()),
)
}
};
let applicability = if checker.comment_ranges().intersects(for_stmt.range()) {
Applicability::Unsafe
} else {
Applicability::Safe
};
checker.diagnostics.push(
Diagnostic::new(
ForLoopWrites {
name: io_object_name.id.to_string(),
},
for_stmt.range,
)
.with_fix(Fix::applicable_edit(
Edit::range_replacement(content, for_stmt.range),
applicability,
)),
);
}

2
crates/ruff_linter/src/rules/refurb/rules/mod.rs
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@ -2,6 +2,7 @@ pub(crate) use bit_count::*;
pub(crate) use check_and_remove_from_set::*;
pub(crate) use delete_full_slice::*;
pub(crate) use for_loop_set_mutations::*;
pub(crate) use for_loop_writes::*;
pub(crate) use fstring_number_format::*;
pub(crate) use hardcoded_string_charset::*;
pub(crate) use hashlib_digest_hex::*;
@ -37,6 +38,7 @@ mod bit_count;
mod check_and_remove_from_set;
mod delete_full_slice;
mod for_loop_set_mutations;
mod for_loop_writes;
mod fstring_number_format;
mod hardcoded_string_charset;
mod hashlib_digest_hex;

161
crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__FURB122_FURB122.py.snap Normal file
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@ -0,0 +1,161 @@
---
source: crates/ruff_linter/src/rules/refurb/mod.rs
---
FURB122.py:8:5: FURB122 [*] Use of `f.write` in a for loop
|
7 | with open("file", "w") as f:
8 | / for line in lines:
9 | | f.write(line)
| |_____________________^ FURB122
10 |
11 | other_line = "other line"
|
= help: Replace with `f.writelines`
ℹ Safe fix
5 5 | # Errors
6 6 |
7 7 | with open("file", "w") as f:
8 |- for line in lines:
9 |- f.write(line)
8 |+ f.writelines(lines)
10 9 |
11 10 | other_line = "other line"
12 11 | with Path("file").open("w") as f:
FURB122.py:13:5: FURB122 [*] Use of `f.write` in a for loop
|
11 | other_line = "other line"
12 | with Path("file").open("w") as f:
13 | / for line in lines:
14 | | f.write(other_line)
| |___________________________^ FURB122
15 |
16 | with Path("file").open("w") as f:
|
= help: Replace with `f.writelines`
ℹ Safe fix
10 10 |
11 11 | other_line = "other line"
12 12 | with Path("file").open("w") as f:
13 |- for line in lines:
14 |- f.write(other_line)
13 |+ f.writelines(other_line for line in lines)
15 14 |
16 15 | with Path("file").open("w") as f:
17 16 | for line in lines:
FURB122.py:17:5: FURB122 [*] Use of `f.write` in a for loop
|
16 | with Path("file").open("w") as f:
17 | / for line in lines:
18 | | f.write(line)
| |_____________________^ FURB122
19 |
20 | with Path("file").open("wb") as f:
|
= help: Replace with `f.writelines`
ℹ Safe fix
14 14 | f.write(other_line)
15 15 |
16 16 | with Path("file").open("w") as f:
17 |- for line in lines:
18 |- f.write(line)
17 |+ f.writelines(lines)
19 18 |
20 19 | with Path("file").open("wb") as f:
21 20 | for line in lines:
FURB122.py:21:5: FURB122 [*] Use of `f.write` in a for loop
|
20 | with Path("file").open("wb") as f:
21 | / for line in lines:
22 | | f.write(line.encode())
| |______________________________^ FURB122
23 |
24 | with Path("file").open("w") as f:
|
= help: Replace with `f.writelines`
ℹ Safe fix
18 18 | f.write(line)
19 19 |
20 20 | with Path("file").open("wb") as f:
21 |- for line in lines:
22 |- f.write(line.encode())
21 |+ f.writelines(line.encode() for line in lines)
23 22 |
24 23 | with Path("file").open("w") as f:
25 24 | for line in lines:
FURB122.py:25:5: FURB122 [*] Use of `f.write` in a for loop
|
24 | with Path("file").open("w") as f:
25 | / for line in lines:
26 | | f.write(line.upper())
| |_____________________________^ FURB122
27 |
28 | with Path("file").open("w") as f:
|
= help: Replace with `f.writelines`
ℹ Safe fix
22 22 | f.write(line.encode())
23 23 |
24 24 | with Path("file").open("w") as f:
25 |- for line in lines:
26 |- f.write(line.upper())
25 |+ f.writelines(line.upper() for line in lines)
27 26 |
28 27 | with Path("file").open("w") as f:
29 28 | pass
FURB122.py:31:5: FURB122 [*] Use of `f.write` in a for loop
|
29 | pass
30 |
31 | / for line in lines:
32 | | f.write(line)
| |_____________________^ FURB122
33 |
34 | # Offer unsafe fix if it would delete comments
|
= help: Replace with `f.writelines`
ℹ Safe fix
28 28 | with Path("file").open("w") as f:
29 29 | pass
30 30 |
31 |- for line in lines:
32 |- f.write(line)
31 |+ f.writelines(lines)
33 32 |
34 33 | # Offer unsafe fix if it would delete comments
35 34 | with open("file","w") as f:
FURB122.py:36:5: FURB122 [*] Use of `f.write` in a for loop
|
34 | # Offer unsafe fix if it would delete comments
35 | with open("file","w") as f:
36 | / for line in lines:
37 | | # a really important comment
38 | | f.write(line)
| |_____________________^ FURB122
39 |
40 | # OK
|
= help: Replace with `f.writelines`
ℹ Unsafe fix
33 33 |
34 34 | # Offer unsafe fix if it would delete comments
35 35 | with open("file","w") as f:
36 |- for line in lines:
37 |- # a really important comment
38 |- f.write(line)
36 |+ f.writelines(lines)
39 37 |
40 38 | # OK
41 39 |

1
ruff.schema.json generated
View file

@ -3277,6 +3277,7 @@
"FURB116",
"FURB118",
"FURB12",
"FURB122",
"FURB129",
"FURB13",
"FURB131",