[`pylint`] Implement auto-fix for `missing-maxsplit-arg` (`PLC0207`) #19387

junhsonjb · 2025-07-16T18:16:14Z

Summary

As a follow-up to #18949 (suggested here), this PR implements auto-fix logic for PLC0207.

Test Plan

Existing tests pass, with updates to the snapshot so that it expects the new output that comes along with the auto-fix.

crates/ruff/tests/lint.rs

github-actions · 2025-07-16T18:27:07Z

`ruff-ecosystem` results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+62 -62 violations, +0 -0 fixes in 13 projects; 42 projects unchanged)

PlasmaPy/PlasmaPy (+1 -1 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- noxfile.py:453:16: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ noxfile.py:453:16: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.

apache/airflow (+11 -11 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview --select ALL

- dev/backport/update_backport_status.py:78:21: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ dev/backport/update_backport_status.py:78:21: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- dev/breeze/src/airflow_breeze/commands/common_options.py:502:26: PLC0207 Pass `maxsplit=1` into `str.split()`
+ dev/breeze/src/airflow_breeze/commands/common_options.py:502:26: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- dev/breeze/src/airflow_breeze/commands/release_management_commands.py:2633:50: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:2633:50: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- dev/breeze/src/airflow_breeze/prepare_providers/provider_documentation.py:714:34: PLC0207 Pass `maxsplit=1` into `str.split()`
+ dev/breeze/src/airflow_breeze/prepare_providers/provider_documentation.py:714:34: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- dev/breeze/src/airflow_breeze/utils/run_utils.py:120:25: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ dev/breeze/src/airflow_breeze/utils/run_utils.py:120:25: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
... 12 additional changes omitted for project

apache/superset (+2 -2 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview --select ALL

- tests/common/query_context_generator.py:214:29: PLC0207 Pass `maxsplit=1` into `str.split()`
+ tests/common/query_context_generator.py:214:29: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- tests/common/query_context_generator.py:255:22: PLC0207 Pass `maxsplit=1` into `str.split()`
+ tests/common/query_context_generator.py:255:22: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

bokeh/bokeh (+3 -3 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview --select ALL

- src/bokeh/io/notebook.py:663:26: PLC0207 Pass `maxsplit=1` into `str.split()`
+ src/bokeh/io/notebook.py:663:26: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- src/bokeh/util/token.py:142:41: PLC0207 Pass `maxsplit=1` into `str.split()`
+ src/bokeh/util/token.py:142:41: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- src/bokeh/util/token.py:155:41: PLC0207 Pass `maxsplit=1` into `str.split()`
+ src/bokeh/util/token.py:155:41: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

freedomofpress/securedrop (+1 -1 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- securedrop/store.py:345:49: PLC0207 Pass `maxsplit=1` into `str.split()`
+ securedrop/store.py:345:49: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

ibis-project/ibis (+1 -1 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- ibis/examples/gen_registry.py:125:52: PLC0207 Pass `maxsplit=1` into `str.split()`
+ ibis/examples/gen_registry.py:125:52: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

langchain-ai/langchain (+22 -22 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- libs/core/langchain_core/_api/deprecation.py:360:17: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ libs/core/langchain_core/_api/deprecation.py:360:17: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- libs/core/langchain_core/_api/deprecation.py:360:56: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ libs/core/langchain_core/_api/deprecation.py:360:56: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- libs/core/langchain_core/_api/deprecation.py:368:17: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ libs/core/langchain_core/_api/deprecation.py:368:17: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- libs/core/langchain_core/_api/deprecation.py:369:16: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ libs/core/langchain_core/_api/deprecation.py:369:16: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- libs/core/langchain_core/_api/deprecation.py:473:24: PLC0207 Pass `maxsplit=1` into `str.split()`
+ libs/core/langchain_core/_api/deprecation.py:473:24: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- libs/core/langchain_core/_api/deprecation.py:492:27: PLC0207 Pass `maxsplit=1` into `str.split()`
+ libs/core/langchain_core/_api/deprecation.py:492:27: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- libs/core/langchain_core/runnables/graph_mermaid.py:157:24: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ libs/core/langchain_core/runnables/graph_mermaid.py:157:24: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- libs/core/langchain_core/utils/mustache.py:85:19: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ libs/core/langchain_core/utils/mustache.py:85:19: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- libs/core/langchain_core/utils/utils.py:140:32: PLC0207 Pass `maxsplit=1` into `str.split()`
... 27 additional changes omitted for project

pandas-dev/pandas (+1 -1 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- pandas/compat/_optional.py:165:14: PLC0207 Pass `maxsplit=1` into `str.split()`
+ pandas/compat/_optional.py:165:14: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

pypa/cibuildwheel (+3 -3 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- bin/update_pythons.py:158:22: PLC0207 Pass `maxsplit=1` into `str.split()`
+ bin/update_pythons.py:158:22: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- cibuildwheel/platforms/macos.py:153:31: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ cibuildwheel/platforms/macos.py:153:31: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- cibuildwheel/selector.py:79:26: PLC0207 Pass `maxsplit=1` into `str.split()`
+ cibuildwheel/selector.py:79:26: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

zulip/zulip (+12 -12 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview --select ALL

- zerver/lib/send_email.py:287:16: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ zerver/lib/send_email.py:287:16: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- zerver/lib/send_email.py:429:21: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ zerver/lib/send_email.py:429:21: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- zerver/lib/upload/local.py:67:17: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ zerver/lib/upload/local.py:67:17: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- zerver/lib/upload/s3.py:176:25: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ zerver/lib/upload/s3.py:176:25: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.
- zerver/lib/webhooks/common.py:249:26: PLC0207 Pass `maxsplit=1` into `str.split()`
+ zerver/lib/webhooks/common.py:249:26: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
... 14 additional changes omitted for project

wntrblm/nox (+1 -1 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- tests/test_sessions.py:1199:44: PLC0207 Instead of `str.split()`, call `str.rsplit()` and pass `maxsplit=1`
+ tests/test_sessions.py:1199:44: PLC0207 [*] Replace with `rsplit(..., maxsplit=1)`.

pytest-dev/pytest (+3 -3 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- src/_pytest/config/findpaths.py:160:16: PLC0207 Pass `maxsplit=1` into `str.split()`
+ src/_pytest/config/findpaths.py:160:16: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- src/_pytest/terminal.py:1012:40: PLC0207 Pass `maxsplit=1` into `str.split()`
+ src/_pytest/terminal.py:1012:40: PLC0207 [*] Replace with `split(..., maxsplit=1)`.
- src/_pytest/terminal.py:462:41: PLC0207 Pass `maxsplit=1` into `str.split()`
+ src/_pytest/terminal.py:462:41: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

astropy/astropy (+1 -1 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- astropy/io/ascii/latex.py:438:16: PLC0207 Pass `maxsplit=1` into `str.split()`
+ astropy/io/ascii/latex.py:438:16: PLC0207 [*] Replace with `split(..., maxsplit=1)`.

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
PLC0207	124	62	62	0	0

@zanieb

## Summary This came up on [Discord](https://discord.com/channels/1039017663004942429/1343692072921731082/1395447082520678440) and also in #19387, but on macOS the tmp directory is a symlink to `/private/tmp`, which breaks this filter. I'm still not quite sure why only these tests are affected when we use the `tempdir_filter` elsewhere, but hopefully this fixes the immediate issue. Just `tempdir.path().canonicalize()` also worked, but I used `dunce` since that's what I saw in other tests (I guess it's not _just_ these tests). Some related links from uv: - https://github.com/astral-sh/uv/blob/1b2f212e8b2f91069b858cb7f5905589c9d15add/crates/uv/tests/it/common/mod.rs#L1161-L1178 - https://github.com/astral-sh/uv/blob/1b2f212e8b2f91069b858cb7f5905589c9d15add/crates/uv/tests/it/common/mod.rs#L424-L438 - astral-sh/uv#14290 Thanks to @zanieb for those! ## Test Plan I tested the `main` branch on my MacBook and reproduced the test failure, then confirmed that the tests pass after the change. Now to make sure it passes on Windows, which caused most of the trouble in the first PR!

ntBre

Thanks, this is looking good! I just had some ideas/questions about the diagnostic messages and fix safety.

ntBre · 2025-07-21T20:49:00Z

crates/ruff_linter/src/rules/pylint/rules/missing_maxsplit_arg.rs

+        if actual_split_type == suggested_split_type {
+            format!("Pass `maxsplit=1` into `str.{actual_split_type}()`")
+        } else {
+            format!("Use `str.{suggested_split_type}()` and pass `maxsplit=1`")
+        }


These look quite repetitive with the message above, especially the first case, which is exactly the same. How hard would it be to make a message like:

Replace with `{suggested_split_type}(..., maxsplit=1)`.

I don't really love that either, but I don't think we should duplicate the message. Ideally we could include the actual variable name and pattern, but that would require a bit of extra work.

Another option might be changing message to something more general instead. I think the more detailed suggestion is a better fit here in fix_title, especially since it's AlwaysFixable.

What do you think?

I agree that the message and fix_title are redundant and that it's better to have more detail in the fix_title. I also agree that including the actual variable name and pattern is ideal, but I think that might fall out of the scope for this PR. Perhaps we go with a more general message and leave that as a potential follow-up?

I think since this is AlwaysFixable we can get away with a general message especially because the fix_title will always be there to provide more detail. How does that sound to you?

That sounds good to me!

ntBre · 2025-07-21T20:56:05Z

crates/ruff_linter/src/rules/pylint/rules/missing_maxsplit_arg.rs

+        SliceBoundary::Last => "rsplit",
+    };
+
+    let maxsplit_argument_edit = fix::edits::add_argument(


I was checking if other calls to add_argument were safe or not, and I found a few examples like this:

ruff/crates/ruff_linter/src/rules/pylint/rules/subprocess_run_without_check.rs

Lines 77 to 93 in cabdd96

add_argument(

"check=False",

&call.arguments,

checker.comment_ranges(),

checker.locator().contents(),

),

// If the function call contains `**kwargs`, mark the fix as unsafe.

if call

.arguments

.keywords

.iter()

.any(|keyword| keyword.arg.is_none())

{

Applicability::Unsafe

} else {

Applicability::Safe

},

I think we should probably do the same here and also add a ## Fix safety section to the docs. I can't think of another reason it would be unsafe because we shouldn't be able to delete any comments with these edits.

Here's a PR adding one of these, for a ## Fix safety example too:

https://github.com/astral-sh/ruff/pull/9176/files

...les/pylint/snapshots/ruff_linter__rules__pylint__tests__PLC0207_missing_maxsplit_arg.py.snap

junhsonjb · 2025-07-25T14:11:24Z

Thanks for the comments, in addition to the updated message that we discussed, I added the ## Fix Safety like you suggested and marked the fix as unsafe when **kwargs is present! Let me know what you think of the changes!

ntBre

Thank you!

junhsonjb commented Jul 16, 2025

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crates/ruff/tests/lint.rs Outdated Show resolved Hide resolved

junhsonjb mentioned this pull request Jul 16, 2025

[pylint] Update missing-maxsplit-arg docs and error to suggest proper usage (PLC0207) #18949

Merged

ntBre self-requested a review July 16, 2025 19:12

ntBre mentioned this pull request Jul 17, 2025

Canonicalize path before filtering #19407

Merged

autofix for PLC0207 -- with rebase to latest main

d5d89c2

junhsonjb force-pushed the jjb-maxsplit-autofix branch from 0ecc0ed to d5d89c2 Compare July 18, 2025 11:37

ntBre added fixes Related to suggested fixes for violations preview Related to preview mode features labels Jul 21, 2025

ntBre reviewed Jul 21, 2025

View reviewed changes

better message, add fix safety to docs and make unsafe for kwargs

5e9db57

junhsonjb requested a review from ntBre July 25, 2025 14:11

ntBre approved these changes Jul 28, 2025

View reviewed changes

ntBre merged commit 6d0f3ef into astral-sh:main Jul 28, 2025
35 checks passed

BrewTestBot mentioned this pull request Jul 29, 2025

ruff 0.12.7 Homebrew/homebrew-core#231689

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[`pylint`] Implement auto-fix for `missing-maxsplit-arg` (`PLC0207`) #19387

[`pylint`] Implement auto-fix for `missing-maxsplit-arg` (`PLC0207`) #19387

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	add_argument(
	"check=False",
	&call.arguments,
	checker.comment_ranges(),
	checker.locator().contents(),
	),
	// If the function call contains `**kwargs`, mark the fix as unsafe.
	if call
	.arguments
	.keywords
	.iter()
	.any(\|keyword\| keyword.arg.is_none())
	{
	Applicability::Unsafe
	} else {
	Applicability::Safe
	},

[pylint] Implement auto-fix for missing-maxsplit-arg (PLC0207) #19387

[pylint] Implement auto-fix for missing-maxsplit-arg (PLC0207) #19387

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[`pylint`] Implement auto-fix for `missing-maxsplit-arg` (`PLC0207`) #19387

[`pylint`] Implement auto-fix for `missing-maxsplit-arg` (`PLC0207`) #19387

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