[`ruff`] Add fix for `none-not-at-end-of-union` (`RUF036`) by anishgirianish · Pull Request #22829 · astral-sh/ruff

anishgirianish · 2026-01-24T04:02:46Z

Summary

Adds an autofix for RUF036 that moves None to the end of union type annotations.

Closes #15136

The fix:

Preserves the union style (PEP 604 | vs typing.Union)
Preserves duplicate None values instead of deduplicating
Skips nested unions to avoid flattening (e.g., None | Union[int, str])
Marked unsafe when comments are present in the annotation

Test Plan

cargo nextest run -p ruff_linter - added test cases for nested unions, comments,
default arguments, and mixed styles.

crates/ruff_linter/src/rules/ruff/rules/none_not_at_end_of_union.rs

anishgirianish · 2026-02-14T07:33:37Z

@amyreese Thanks for the review! I've addressed all the feedback:

Changed "type annotation" to "type union" in the message and fix title
Refactored generate_pep604_fix and generate_typing_union_fix to return Edit, building the Fix in generate_fix
Removed .copied() by simplifying to [other_exprs, none_exprs].concat()

Ready for another look whenever you have a chance. Thank you!

astral-sh-bot · 2026-02-14T07:36:07Z

`ruff-ecosystem` results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+395 -395 violations, +0 -0 fixes in 18 projects; 38 projects unchanged)

DisnakeDev/disnake (+10 -10 violations, +0 -0 fixes)

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

+ disnake/gateway.py:287:37: RUF036 [*] `None` not at the end of the type union.
- disnake/gateway.py:287:43: RUF036 `None` not at the end of the type annotation.
+ disnake/i18n.py:103:15: RUF036 [*] `None` not at the end of the type union.
- disnake/i18n.py:103:35: RUF036 `None` not at the end of the type annotation.
+ disnake/i18n.py:113:15: RUF036 [*] `None` not at the end of the type union.
- disnake/i18n.py:113:35: RUF036 `None` not at the end of the type annotation.
+ disnake/i18n.py:137:44: RUF036 [*] `None` not at the end of the type union.
- disnake/i18n.py:137:50: RUF036 `None` not at the end of the type annotation.
+ disnake/i18n.py:30:37: RUF036 [*] `None` not at the end of the type union.
- disnake/i18n.py:30:43: RUF036 `None` not at the end of the type annotation.
... 10 additional changes omitted for project

RasaHQ/rasa (+3 -3 violations, +0 -0 fixes)

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

+ rasa/shared/core/events.py:597:42: RUF036 [*] `None` not at the end of the type union.
- rasa/shared/core/events.py:597:48: RUF036 `None` not at the end of the type annotation.
+ rasa/shared/core/events.py:624:25: RUF036 [*] `None` not at the end of the type union.
- rasa/shared/core/events.py:624:31: RUF036 `None` not at the end of the type annotation.
+ rasa/utils/tensorflow/models.py:247:29: RUF036 [*] `None` not at the end of the type union.
- rasa/utils/tensorflow/models.py:247:35: RUF036 `None` not at the end of the type annotation.

apache/airflow (+108 -108 violations, +0 -0 fixes)

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

+ airflow-core/src/airflow/api_fastapi/common/parameters.py:1086:22: RUF036 [*] `None` not at the end of the type union.
- airflow-core/src/airflow/api_fastapi/common/parameters.py:1086:22: RUF036 `None` not at the end of the type annotation.
+ airflow-core/src/airflow/api_fastapi/common/parameters.py:203:20: RUF036 [*] `None` not at the end of the type union.
- airflow-core/src/airflow/api_fastapi/common/parameters.py:203:20: RUF036 `None` not at the end of the type annotation.
+ airflow-core/src/airflow/api_fastapi/common/parameters.py:206:22: RUF036 [*] `None` not at the end of the type union.
- airflow-core/src/airflow/api_fastapi/common/parameters.py:206:22: RUF036 `None` not at the end of the type annotation.
+ airflow-core/src/airflow/api_fastapi/common/parameters.py:210:26: RUF036 [*] `None` not at the end of the type union.
- airflow-core/src/airflow/api_fastapi/common/parameters.py:210:26: RUF036 `None` not at the end of the type annotation.
+ airflow-core/src/airflow/api_fastapi/core_api/routes/public/auth.py:38:65: RUF036 [*] `None` not at the end of the type union.
- airflow-core/src/airflow/api_fastapi/core_api/routes/public/auth.py:38:65: RUF036 `None` not at the end of the type annotation.
+ airflow-core/src/airflow/example_dags/plugins/event_listener.py:102:12: RUF036 [*] `None` not at the end of the type union.
- airflow-core/src/airflow/example_dags/plugins/event_listener.py:102:12: RUF036 `None` not at the end of the type annotation.
+ airflow-core/src/airflow/executors/base_executor.py:155:13: RUF036 [*] `None` not at the end of the type union.
... 203 additional changes omitted for project

apache/superset (+4 -4 violations, +0 -0 fixes)

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

+ superset/config.py:1511:5: RUF036 [*] `None` not at the end of the type union.
- superset/config.py:1511:5: RUF036 `None` not at the end of the type annotation.
+ superset/config.py:2271:43: RUF036 [*] `None` not at the end of the type union.
- superset/config.py:2271:43: RUF036 `None` not at the end of the type annotation.
+ superset/db_engine_specs/gsheets.py:310:26: RUF036 [*] `None` not at the end of the type union.
- superset/db_engine_specs/gsheets.py:310:26: RUF036 `None` not at the end of the type annotation.
+ superset/jinja_context.py:101:10: RUF036 [*] `None` not at the end of the type union.
- superset/jinja_context.py:101:16: RUF036 `None` not at the end of the type annotation.

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

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

+ src/bokeh/client/websocket.py:73:85: RUF036 [*] `None` not at the end of the type union.
- src/bokeh/client/websocket.py:73:85: RUF036 `None` not at the end of the type annotation.
+ src/bokeh/embed/standalone.py:84:24: RUF036 [*] `None` not at the end of the type union.
- src/bokeh/embed/standalone.py:84:30: RUF036 `None` not at the end of the type annotation.
+ src/bokeh/util/tornado.py:231:26: RUF036 [*] `None` not at the end of the type union.
- src/bokeh/util/tornado.py:231:26: RUF036 `None` not at the end of the type annotation.

ibis-project/ibis (+2 -2 violations, +0 -0 fixes)

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

+ ibis/backends/__init__.py:1294:54: RUF036 [*] `None` not at the end of the type union.
- ibis/backends/__init__.py:1294:54: RUF036 `None` not at the end of the type annotation.
+ ibis/backends/sql/__init__.py:726:43: RUF036 [*] `None` not at the end of the type union.
- ibis/backends/sql/__init__.py:726:43: RUF036 `None` not at the end of the type annotation.

langchain-ai/langchain (+10 -10 violations, +0 -0 fixes)

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

+ libs/langchain/langchain_classic/evaluation/parsing/base.py:152:10: RUF036 [*] `None` not at the end of the type union.
- libs/langchain/langchain_classic/evaluation/parsing/base.py:152:24: RUF036 `None` not at the end of the type annotation.
+ libs/langchain/langchain_classic/evaluation/parsing/json_distance.py:94:41: RUF036 [*] `None` not at the end of the type union.
- libs/langchain/langchain_classic/evaluation/parsing/json_distance.py:94:55: RUF036 `None` not at the end of the type annotation.
+ libs/langchain/langchain_classic/evaluation/parsing/json_schema.py:67:41: RUF036 [*] `None` not at the end of the type union.
- libs/langchain/langchain_classic/evaluation/parsing/json_schema.py:67:55: RUF036 `None` not at the end of the type annotation.
+ libs/langchain/langchain_classic/indexes/_sql_record_manager.py:93:17: RUF036 [*] `None` not at the end of the type union.
- libs/langchain/langchain_classic/indexes/_sql_record_manager.py:93:17: RUF036 `None` not at the end of the type annotation.
+ libs/langchain_v1/langchain/agents/middleware/types.py:806:10: RUF036 [*] `None` not at the end of the type union.
- libs/langchain_v1/langchain/agents/middleware/types.py:806:42: RUF036 `None` not at the end of the type annotation.
... 10 additional changes omitted for project

latchbio/latch (+6 -6 violations, +0 -0 fixes)

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

+ src/latch/registry/types.py:38:43: RUF036 [*] `None` not at the end of the type union.
- src/latch/registry/types.py:47:5: RUF036 `None` not at the end of the type annotation.
+ src/latch/types/metadata.py:419:28: RUF036 [*] `None` not at the end of the type union.
- src/latch/types/metadata.py:420:5: RUF036 `None` not at the end of the type annotation.
+ src/latch_cli/services/get.py:38:26: RUF036 [*] `None` not at the end of the type union.
- src/latch_cli/services/get.py:38:32: RUF036 `None` not at the end of the type annotation.
+ src/latch_cli/snakemake/config/utils.py:200:50: RUF036 [*] `None` not at the end of the type union.
- src/latch_cli/snakemake/config/utils.py:200:56: RUF036 `None` not at the end of the type annotation.
+ src/latch_cli/snakemake/config/utils.py:25:24: RUF036 [*] `None` not at the end of the type union.
- src/latch_cli/snakemake/config/utils.py:25:53: RUF036 `None` not at the end of the type annotation.
... 2 additional changes omitted for project

milvus-io/pymilvus (+1 -1 violations, +0 -0 fixes)

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

+ pymilvus/client/search_result.py:888:51: RUF036 [*] `None` not at the end of the type union.
- pymilvus/client/search_result.py:888:57: RUF036 `None` not at the end of the type annotation.

pandas-dev/pandas (+45 -45 violations, +0 -0 fixes)

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

+ pandas/_libs/json.pyi:14:22: RUF036 [*] `None` not at the end of the type union.
- pandas/_libs/json.pyi:14:22: RUF036 `None` not at the end of the type annotation.
+ pandas/_libs/tslibs/timedeltas.pyi:147:36: RUF036 [*] `None` not at the end of the type union.
- pandas/_libs/tslibs/timedeltas.pyi:147:36: RUF036 `None` not at the end of the type annotation.
+ pandas/_libs/tslibs/timestamps.pyi:31:25: RUF036 [*] `None` not at the end of the type union.
- pandas/_libs/tslibs/timestamps.pyi:31:41: RUF036 `None` not at the end of the type annotation.
+ pandas/core/arrays/datetimelike.py:1075:45: RUF036 [*] `None` not at the end of the type union.
- pandas/core/arrays/datetimelike.py:1075:45: RUF036 `None` not at the end of the type annotation.
+ pandas/core/dtypes/cast.py:186:29: RUF036 [*] `None` not at the end of the type union.
- pandas/core/dtypes/cast.py:186:38: RUF036 `None` not at the end of the type annotation.
... 80 additional changes omitted for project

python/typeshed (+143 -143 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --no-fix --output-format concise --preview --select E,F,FA,I,PYI,RUF,UP,W

+ stdlib/_interpreters.pyi:30:6: RUF036 [*] `None` not at the end of the type union.
- stdlib/_interpreters.pyi:30:6: RUF036 `None` not at the end of the type annotation.
+ stdlib/_ssl.pyi:82:58: RUF036 [*] `None` not at the end of the type union.
- stdlib/_ssl.pyi:82:58: RUF036 `None` not at the end of the type annotation.
+ stdlib/ast.pyi:1096:51: RUF036 [*] `None` not at the end of the type union.
- stdlib/ast.pyi:1096:96: RUF036 `None` not at the end of the type annotation.
+ stdlib/ast.pyi:1099:51: RUF036 [*] `None` not at the end of the type union.
- stdlib/ast.pyi:1099:96: RUF036 `None` not at the end of the type annotation.
+ stdlib/ast.pyi:1754:26: RUF036 [*] `None` not at the end of the type union.
- stdlib/ast.pyi:1754:26: RUF036 `None` not at the end of the type annotation.
+ stdlib/ast.pyi:1764:26: RUF036 [*] `None` not at the end of the type union.
- stdlib/ast.pyi:1764:26: RUF036 `None` not at the end of the type annotation.
+ stdlib/ast.pyi:1774:26: RUF036 [*] `None` not at the end of the type union.
- stdlib/ast.pyi:1774:26: RUF036 `None` not at the end of the type annotation.
+ stdlib/ast.pyi:1784:26: RUF036 [*] `None` not at the end of the type union.
- stdlib/ast.pyi:1784:26: RUF036 `None` not at the end of the type annotation.
+ stdlib/ast.pyi:1794:26: RUF036 [*] `None` not at the end of the type union.
- stdlib/ast.pyi:1794:26: RUF036 `None` not at the end of the type annotation.
... 268 additional changes omitted for project

... Truncated remaining completed project reports due to GitHub comment length restrictions

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
RUF036	790	395	395	0	0

ntBre · 2026-02-23T20:04:12Z

Thanks @anishgirianish for working on this! I haven't looked at the diff yet, so apologies if you've addressed all of these, but I was hoping you could check whether or not you had resolved my comment on a previous version of this PR? See #18964 (review) and the comments it links to on an even earlier version. I think that's a good summary of the missing pieces from the earlier iterations and would help me get started reviewing this PR.

anishgirianish · 2026-02-23T20:11:20Z

Thanks @anishgirianish for working on this! I haven't looked at the diff yet, so apologies if you've addressed all of these, but I was hoping you could check whether or not you had resolved my comment on a previous version of this PR? See #18964 (review) and the comments it links to on an even earlier version. I think that's a good summary of the missing pieces from the earlier iterations and would help me get started reviewing this PR.

Sure will do thanks

crates/ruff_linter/src/rules/ruff/rules/none_not_at_end_of_union.rs

amyreese · 2026-02-27T02:46:45Z

LGTM, unless @ntBre knows of any relevant helpers that could be reused.

ntBre

Thank you! This looks great to me overall, I just had one concern about fixes that generate None | None. I'd be okay just skipping fixes in cases with multiple Nones, but I'm curious what you and Amy think.

.../ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF036_RUF036.py.snap

anishgirianish · 2026-02-27T16:19:46Z

Thank you! This looks great to me overall, I just had one concern about fixes that generate None | None. I'd be okay just skipping fixes in cases with multiple Nones, but I'm curious what you and Amy think.

Thank you for the review! I've skipped the fix for PEP 604 unions with multiple Nones to avoid generating None | None. Ready for another look whenever you get a chance!

ntBre

Looks good to me! I'll leave it to Amy to merge.

crates/ruff_linter/src/rules/ruff/rules/none_not_at_end_of_union.rs

anishgirianish · 2026-02-27T19:05:34Z

@amyreese thank you for the latest commit. I really appreciate it

* main: [ty] Take myself out of the reviewer pool for the next few days (#23618) [ty] Fix bug where ty would think that a `Callable` with a variadic positional parameter could be a subtype of a `Callable` with a positional-or-keyword parameter (#23610) [`ruff`] Add fix for `none-not-at-end-of-union` (`RUF036`) (#22829) Bump cargo dist to 0.31 (#23614) [`pyflakes`] Fix false positive for names shadowing re-exports (`F811`) (#23356) [`fastapi`] Handle callable class dependencies with `__call__` method (`FAST003`) (#23553) [ty] Recurse into tuples and nested tuples when applying special-cased validation of `isinstance()` and `issubclass()` (#23607) Update typing conformance suite commit (#23606) [ty] Detect invalid uses of `@final` on non-methods (#23604) [ty] Move the type hierarchy request handlers to individual modules [ty] Wire up the type hierarchy implementation with the LSP [ty] Add routine for mapping from system path to vendored path [ty] Implement internal routines for providing the LSP "type hierarchy" feature [ty] Add some helper methods on `ClassLiteral` [ty] Move some module name helper routines to methods on `ModuleName` [ty] Bump version of `lsp-types` [ty] Refactor to support building constraint sets differently (#23600) [ty] Dataclass transform: neither frozen nor non-frozen (#23366) [ty] Add snapshot tests for advanced `invalid-assignment` scenarios (#23581) [ty] disallow negative narrowing on SubclassOf types (#23598)

anishgirianish added 2 commits January 23, 2026 21:54

[] Add fix for none-not-at-end-of-union ()

0ac1712

clean ups

6fc3dcb

anishgirianish changed the title ~~[ruff] Add fix for none-not-at-end-of-union (RUF036)~~ [ruff] Add fix for none-not-at-end-of-union (RUF036) Jan 24, 2026

anishgirianish mentioned this pull request Jan 24, 2026

Feature request: Autofix for none-not-at-end-of-union (RUF036) #15136

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amyreese requested a review from ntBre February 13, 2026 23:07

amyreese reviewed Feb 13, 2026

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[RUF036] refactor

20730d9

anishgirianish requested a review from amyreese February 14, 2026 07:33

anishgirianish added 3 commits February 24, 2026 18:00

[ruff] addressed review comments and refactor

d0235ca

Merge remote-tracking branch 'upstream/main' into feat/ruf036-autofix

73a390c

[ruff] clean ups

7cec1d7

amyreese reviewed Feb 26, 2026

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anishgirianish added 3 commits February 25, 2026 23:27

[ruff] bump rule set

b205422

revert unecesearcy changes

3f4b642

[ruff] refactor clean ups

8881e35

anishgirianish requested a review from amyreese February 26, 2026 06:14

ntBre added fixes Related to suggested fixes for violations preview Related to preview mode features labels Feb 26, 2026

amyreese self-assigned this Feb 27, 2026

amyreese approved these changes Feb 27, 2026

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anishgirianish added 2 commits February 27, 2026 09:50

[ruff] Skip fix for PEP 604 unions with multiple s

e1e6119

[fix] fix faling ci lint

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anishgirianish requested a review from ntBre February 27, 2026 16:20

ntBre approved these changes Feb 27, 2026

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ntBre changed the title ~~[ruff] Add fix for none-not-at-end-of-union (RUF036)~~ [ruff] Add fix for none-not-at-end-of-union (RUF036) Feb 27, 2026

Apply Brent's suggestions

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amyreese enabled auto-merge (squash) February 27, 2026 18:56

amyreese merged commit b02cdac into astral-sh:main Feb 27, 2026
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BrewTestBot mentioned this pull request Mar 5, 2026

ruff 0.15.5 Homebrew/homebrew-core#270824

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anishgirianish commented Jan 24, 2026

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