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Merged
ntBre merged 2 commits into from
Jan 29, 2026
Merged

Stabilize PLC0207 #22918

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a55cab6
Stabilize `PLC0207`
ntBre Jan 28, 2026
8ab00e6
simplify diagnostic `message` and use `&'a str`
ntBre Jan 28, 2026
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32 changes: 14 additions & 18 deletions crates/ruff_linter/src/rules/pylint/rules/missing_maxsplit_arg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,13 +11,13 @@ use crate::fix;
use crate::{AlwaysFixableViolation, Applicability, Edit, Fix};

/// ## What it does
/// Checks for access to the first or last element of `str.split()` or `str.rsplit()` without
/// `maxsplit=1`
/// Checks for access to the first or last element of `str.split()` or `str.rsplit()` without a
/// `maxsplit=1` argument.
///
/// ## Why is this bad?
/// Calling `str.split()` or `str.rsplit()` without passing `maxsplit=1` splits on every delimiter in the
/// string. When accessing only the first or last element of the result, it
/// would be more efficient to only split once.
/// would be more efficient to split only once.
///
/// ## Example
/// ```python
Expand All @@ -38,13 +38,14 @@ use crate::{AlwaysFixableViolation, Applicability, Edit, Fix};
/// ```
///
/// ## Fix Safety
/// This rule's fix is marked as unsafe for `split()`/`rsplit()` calls that contain `*args` or `**kwargs` arguments, as
/// adding a `maxsplit` argument to such a call may lead to duplicated arguments.
/// This rule's fix is marked as unsafe for `split()`/`rsplit()` calls that contain `*args` or
/// `**kwargs` arguments, as adding a `maxsplit` argument to such a call may lead to duplicate
/// arguments.
#[derive(ViolationMetadata)]
#[violation_metadata(preview_since = "0.11.12")]
pub(crate) struct MissingMaxsplitArg {
actual_split_type: String,
suggested_split_type: String,
#[violation_metadata(stable_since = "0.15.0")]
pub(crate) struct MissingMaxsplitArg<'a> {
actual_split_type: &'a str,
suggested_split_type: &'a str,
}

/// Represents the index of the slice used for this rule (which can only be 0 or -1)
Expand All @@ -53,15 +54,10 @@ enum SliceBoundary {
Last,
}

impl AlwaysFixableViolation for MissingMaxsplitArg {
impl AlwaysFixableViolation for MissingMaxsplitArg<'_> {
#[derive_message_formats]
fn message(&self) -> String {
let MissingMaxsplitArg {
actual_split_type: _,
suggested_split_type,
} = self;

format!("Replace with `{suggested_split_type}(..., maxsplit=1)`.")
"String is split more times than necessary".to_string()
}

fn fix_title(&self) -> String {
Expand Down Expand Up @@ -189,8 +185,8 @@ pub(crate) fn missing_maxsplit_arg(checker: &Checker, value: &Expr, slice: &Expr

let mut diagnostic = checker.report_diagnostic(
MissingMaxsplitArg {
actual_split_type: actual_split_type.to_string(),
suggested_split_type: suggested_split_type.to_string(),
actual_split_type,
suggested_split_type,
},
expr.range(),
);
Expand Down
72 changes: 36 additions & 36 deletions .../pylint/snapshots/ruff_linter__rules__pylint__tests__PLC0207_missing_maxsplit_arg.py.snap
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
---
source: crates/ruff_linter/src/rules/pylint/mod.rs
---
PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:14:1
|
12 | # Errors
Expand All @@ -21,7 +21,7 @@ help: Pass `maxsplit=1` into `str.split()`
16 | "1,2,3".rsplit(",")[0] # [missing-maxsplit-arg]
17 | "1,2,3".rsplit(",")[-1] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:15:1
|
13 | ## Test split called directly on string literal
Expand All @@ -41,7 +41,7 @@ help: Use `str.rsplit()` and pass `maxsplit=1`
17 | "1,2,3".rsplit(",")[-1] # [missing-maxsplit-arg]
18 |

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:16:1
|
14 | "1,2,3".split(",")[0] # [missing-maxsplit-arg]
Expand All @@ -60,7 +60,7 @@ help: Use `str.split()` and pass `maxsplit=1`
18 |
19 | ## Test split called on string variable

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:17:1
|
15 | "1,2,3".split(",")[-1] # [missing-maxsplit-arg]
Expand All @@ -80,7 +80,7 @@ help: Pass `maxsplit=1` into `str.rsplit()`
19 | ## Test split called on string variable
20 | SEQ.split(",")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:20:1
|
19 | ## Test split called on string variable
Expand All @@ -99,7 +99,7 @@ help: Pass `maxsplit=1` into `str.split()`
22 | SEQ.rsplit(",")[0] # [missing-maxsplit-arg]
23 | SEQ.rsplit(",")[-1] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:21:1
|
19 | ## Test split called on string variable
Expand All @@ -119,7 +119,7 @@ help: Use `str.rsplit()` and pass `maxsplit=1`
23 | SEQ.rsplit(",")[-1] # [missing-maxsplit-arg]
24 |

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:22:1
|
20 | SEQ.split(",")[0] # [missing-maxsplit-arg]
Expand All @@ -138,7 +138,7 @@ help: Use `str.split()` and pass `maxsplit=1`
24 |
25 | ## Test split called on class attribute

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:23:1
|
21 | SEQ.split(",")[-1] # [missing-maxsplit-arg]
Expand All @@ -158,7 +158,7 @@ help: Pass `maxsplit=1` into `str.rsplit()`
25 | ## Test split called on class attribute
26 | Foo.class_str.split(",")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:26:1
|
25 | ## Test split called on class attribute
Expand All @@ -177,7 +177,7 @@ help: Pass `maxsplit=1` into `str.split()`
28 | Foo.class_str.rsplit(",")[0] # [missing-maxsplit-arg]
29 | Foo.class_str.rsplit(",")[-1] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:27:1
|
25 | ## Test split called on class attribute
Expand All @@ -197,7 +197,7 @@ help: Use `str.rsplit()` and pass `maxsplit=1`
29 | Foo.class_str.rsplit(",")[-1] # [missing-maxsplit-arg]
30 |

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:28:1
|
26 | Foo.class_str.split(",")[0] # [missing-maxsplit-arg]
Expand All @@ -216,7 +216,7 @@ help: Use `str.split()` and pass `maxsplit=1`
30 |
31 | ## Test split called on sliced string

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:29:1
|
27 | Foo.class_str.split(",")[-1] # [missing-maxsplit-arg]
Expand All @@ -236,7 +236,7 @@ help: Pass `maxsplit=1` into `str.rsplit()`
31 | ## Test split called on sliced string
32 | "1,2,3"[::-1].split(",")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:32:1
|
31 | ## Test split called on sliced string
Expand All @@ -255,7 +255,7 @@ help: Pass `maxsplit=1` into `str.split()`
34 | SEQ[:3].split(",")[0] # [missing-maxsplit-arg]
35 | Foo.class_str[1:3].split(",")[-1] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:33:1
|
31 | ## Test split called on sliced string
Expand All @@ -275,7 +275,7 @@ help: Pass `maxsplit=1` into `str.split()`
35 | Foo.class_str[1:3].split(",")[-1] # [missing-maxsplit-arg]
36 | "1,2,3"[::-1].rsplit(",")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:34:1
|
32 | "1,2,3"[::-1].split(",")[0] # [missing-maxsplit-arg]
Expand All @@ -295,7 +295,7 @@ help: Pass `maxsplit=1` into `str.split()`
36 | "1,2,3"[::-1].rsplit(",")[0] # [missing-maxsplit-arg]
37 | SEQ[:3].rsplit(",")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:35:1
|
33 | "1,2,3"[::-1][::-1].split(",")[0] # [missing-maxsplit-arg]
Expand All @@ -315,7 +315,7 @@ help: Use `str.rsplit()` and pass `maxsplit=1`
37 | SEQ[:3].rsplit(",")[0] # [missing-maxsplit-arg]
38 | Foo.class_str[1:3].rsplit(",")[-1] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:36:1
|
34 | SEQ[:3].split(",")[0] # [missing-maxsplit-arg]
Expand All @@ -335,7 +335,7 @@ help: Use `str.split()` and pass `maxsplit=1`
38 | Foo.class_str[1:3].rsplit(",")[-1] # [missing-maxsplit-arg]
39 |

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:37:1
|
35 | Foo.class_str[1:3].split(",")[-1] # [missing-maxsplit-arg]
Expand All @@ -354,7 +354,7 @@ help: Use `str.split()` and pass `maxsplit=1`
39 |
40 | ## Test sep given as named argument

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:38:1
|
36 | "1,2,3"[::-1].rsplit(",")[0] # [missing-maxsplit-arg]
Expand All @@ -374,7 +374,7 @@ help: Pass `maxsplit=1` into `str.rsplit()`
40 | ## Test sep given as named argument
41 | "1,2,3".split(sep=",")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:41:1
|
40 | ## Test sep given as named argument
Expand All @@ -393,7 +393,7 @@ help: Pass `maxsplit=1` into `str.split()`
43 | "1,2,3".rsplit(sep=",")[0] # [missing-maxsplit-arg]
44 | "1,2,3".rsplit(sep=",")[-1] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:42:1
|
40 | ## Test sep given as named argument
Expand All @@ -413,7 +413,7 @@ help: Use `str.rsplit()` and pass `maxsplit=1`
44 | "1,2,3".rsplit(sep=",")[-1] # [missing-maxsplit-arg]
45 |

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:43:1
|
41 | "1,2,3".split(sep=",")[0] # [missing-maxsplit-arg]
Expand All @@ -432,7 +432,7 @@ help: Use `str.split()` and pass `maxsplit=1`
45 |
46 | ## Special cases

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:44:1
|
42 | "1,2,3".split(sep=",")[-1] # [missing-maxsplit-arg]
Expand All @@ -452,7 +452,7 @@ help: Pass `maxsplit=1` into `str.rsplit()`
46 | ## Special cases
47 | "1,2,3".split("\n")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:47:1
|
46 | ## Special cases
Expand All @@ -471,7 +471,7 @@ help: Pass `maxsplit=1` into `str.split()`
49 | "1,2,3".rsplit("rsplit")[0] # [missing-maxsplit-arg]
50 |

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:48:1
|
46 | ## Special cases
Expand All @@ -490,7 +490,7 @@ help: Use `str.rsplit()` and pass `maxsplit=1`
50 |
51 | ## Test class attribute named split

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:49:1
|
47 | "1,2,3".split("\n")[0] # [missing-maxsplit-arg]
Expand All @@ -510,7 +510,7 @@ help: Use `str.split()` and pass `maxsplit=1`
51 | ## Test class attribute named split
52 | Bar.split.split(",")[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:52:1
|
51 | ## Test class attribute named split
Expand All @@ -529,7 +529,7 @@ help: Pass `maxsplit=1` into `str.split()`
54 | Bar.split.rsplit(",")[0] # [missing-maxsplit-arg]
55 | Bar.split.rsplit(",")[-1] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:53:1
|
51 | ## Test class attribute named split
Expand All @@ -549,7 +549,7 @@ help: Use `str.rsplit()` and pass `maxsplit=1`
55 | Bar.split.rsplit(",")[-1] # [missing-maxsplit-arg]
56 |

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:54:1
|
52 | Bar.split.split(",")[0] # [missing-maxsplit-arg]
Expand All @@ -568,7 +568,7 @@ help: Use `str.split()` and pass `maxsplit=1`
56 |
57 | ## Test unpacked dict literal kwargs

PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:55:1
|
53 | Bar.split.split(",")[-1] # [missing-maxsplit-arg]
Expand All @@ -588,7 +588,7 @@ help: Pass `maxsplit=1` into `str.rsplit()`
57 | ## Test unpacked dict literal kwargs
58 | "1,2,3".split(**{"sep": ","})[0] # [missing-maxsplit-arg]

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:58:1
|
57 | ## Test unpacked dict literal kwargs
Expand All @@ -606,7 +606,7 @@ help: Pass `maxsplit=1` into `str.split()`
61 | # OK
note: This is an unsafe fix and may change runtime behavior

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:179:1
|
177 | # Errors
Expand All @@ -627,7 +627,7 @@ help: Pass `maxsplit=1` into `str.split()`
182 | "1,2,3".split(",", **kwargs_with_maxsplit)[0] # TODO: false positive
note: This is an unsafe fix and may change runtime behavior

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:182:1
|
180 | # OK
Expand All @@ -648,7 +648,7 @@ help: Pass `maxsplit=1` into `str.split()`
185 |
note: This is an unsafe fix and may change runtime behavior

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:184:1
|
182 | "1,2,3".split(",", **kwargs_with_maxsplit)[0] # TODO: false positive
Expand All @@ -667,7 +667,7 @@ help: Pass `maxsplit=1` into `str.split()`
187 | ## Test unpacked list literal args (starred expressions)
note: This is an unsafe fix and may change runtime behavior

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:189:1
|
187 | ## Test unpacked list literal args (starred expressions)
Expand All @@ -688,7 +688,7 @@ help: Pass `maxsplit=1` into `str.split()`
192 | # Errors
note: This is an unsafe fix and may change runtime behavior

PLC0207 [*] Replace with `split(..., maxsplit=1)`.
PLC0207 [*] String is split more times than necessary
--> missing_maxsplit_arg.py:194:1
|
192 | # Errors
Expand Down