[ty] Detect invalid attribute overrides by charliermarsh · Pull Request #24767 · astral-sh/ruff

charliermarsh · 2026-04-21T13:43:45Z

Summary

We now detect Liskov violations when a parent-child pair have attributes with a differing ClassVar status.

In general, we interpret an attribute without a ClassVar annotation as an instance attribute, with the exception of cases like the following, where we "allow" the child to "inherit" the annotation to adhere to the conformance suite:

class ProtoB(Protocol):
    z: ClassVar[int]

class ProtoBImpl(ProtoB):
    z = 0

Closes astral-sh/ty#3093.

astral-sh-bot · 2026-04-21T13:45:35Z

Typing conformance results improved 🎉

The percentage of diagnostics emitted that were expected errors increased from 87.94% to 87.96%. The percentage of expected errors that received a diagnostic increased from 83.36% to 83.55%. The number of fully passing files improved from 79/133 to 80/133.

Summary

How are test cases classified?

Each test case represents one expected error annotation or a group of annotations sharing a tag. Counts are per test case, not per diagnostic — multiple diagnostics on the same line count as one. Required annotations (E) are true positives when ty flags the expected location and false negatives when it does not. Optional annotations (E?) are true positives when flagged but true negatives (not false negatives) when not. Tagged annotations (E[tag]) require ty to flag exactly one of the tagged lines; tagged multi-annotations (E[tag+]) allow any number up to the tag count. Flagging unexpected locations counts as a false positive.

Metric	Old	New	Diff	Outcome
True Positives	882	884	+2	⏫ (✅)
False Positives	121	121	+0
False Negatives	176	174	-2	⏬ (✅)
Total Diagnostics	1052	1054	+2	⏫
Precision	87.94%	87.96%	+0.02%	⏫ (✅)
Recall	83.36%	83.55%	+0.19%	⏫ (✅)
Passing Files	79/133	80/133	+1	⏫ (✅)

Test file breakdown

1 file altered

File	True Positives	False Positives	False Negatives	Status
dataclasses_inheritance.py	2 (+2) ✅	0	0 (-2) ✅	✅ Newly Passing 🎉
Total (all files)	884 (+2) ✅	121	174 (-2) ✅	80/133

True positives added (2)

2 diagnostics

Test case

Diff

dataclasses_inheritance.py:62

+error[invalid-attribute-override] Invalid override of attribute `x`: class variable cannot override instance variable `DC6.x`

dataclasses_inheritance.py:66

+error[invalid-attribute-override] Invalid override of attribute `y`: instance variable cannot override class variable `DC6.y`

astral-sh-bot · 2026-04-21T13:46:23Z

Memory usage report

Summary

Project	Old	New	Diff	Outcome
sphinx	258.60MB	258.63MB	+0.01% (28.15kB)	⏫
prefect	702.82MB	702.83MB	+0.00% (10.27kB)	⏫
flake8	47.68MB	47.69MB	+0.01% (3.92kB)	⏫
trio	116.46MB	116.46MB	+0.00% (2.42kB)	⏫

Significant changes

Click to expand detailed breakdown

sphinx

Name	Old	New	Diff	Outcome
`Type<'db>::class_member_with_policy_`	7.62MB	7.63MB	+0.23% (18.21kB)	⏫
`Type<'db>::class_member_with_policy_::interned_arguments`	4.02MB	4.03MB	+0.10% (4.16kB)	⏫
`infer_scope_types_impl`	15.36MB	15.36MB	+0.03% (4.03kB)	⏫
`Project`	11.99kB	13.74kB	+14.59% (1.75kB)	⏫

prefect

Name	Old	New	Diff	Outcome
`infer_scope_types_impl`	54.66MB	54.66MB	+0.01% (4.64kB)	⏫
`Type<'db>::class_member_with_policy_`	17.66MB	17.66MB	+0.02% (2.76kB)	⏫
`Project`	18.99kB	20.74kB	+9.21% (1.75kB)	⏫
`Type<'db>::class_member_with_policy_::interned_arguments`	9.82MB	9.82MB	+0.01% (1.12kB)	⏫

flake8

Name	Old	New	Diff	Outcome
`Project`	5.87kB	7.62kB	+29.82% (1.75kB)	⏫
`Type<'db>::class_member_with_policy_`	572.44kB	574.14kB	+0.30% (1.70kB)	⏫
`Type<'db>::class_member_with_policy_::interned_arguments`	311.19kB	311.49kB	+0.10% (312.00B)	⏫
`infer_scope_types_impl`	983.70kB	983.86kB	+0.02% (168.00B)	⏫

trio

Name	Old	New	Diff	Outcome
`Project`	6.74kB	8.49kB	+25.95% (1.75kB)	⏫
`infer_scope_types_impl`	4.71MB	4.71MB	+0.01% (480.00B)	⏫
`Type<'db>::class_member_with_policy_::interned_arguments`	1.12MB	1.12MB	+0.01% (104.00B)	⏫
`Type<'db>::class_member_with_policy_`	2.03MB	2.03MB	+0.00% (100.00B)	⏫

astral-sh-bot · 2026-04-21T13:48:51Z

`ecosystem-analyzer` results

Lint rule	Added	Removed	Changed
`invalid-attribute-override`	55	0	0
Total	55	0	0

Raw diff (55 changes)

archinstall (https://github.com/archlinux/archinstall)
+ archinstall/tui/ui/components.py:43:2 error[invalid-attribute-override] Invalid override of attribute `BINDINGS`: class variable cannot override instance variable `Screen.BINDINGS`
+ archinstall/tui/ui/components.py:369:2 error[invalid-attribute-override] Invalid override of attribute `BINDINGS`: class variable cannot override instance variable `SelectionList.BINDINGS`

dd-trace-py (https://github.com/DataDog/dd-trace-py)
+ ddtrace/contrib/_events/llm.py:40:5 error[invalid-attribute-override] Invalid override of attribute `span_type`: instance variable cannot override class variable `TracingEvent.span_type`

discord.py (https://github.com/Rapptz/discord.py)
+ discord/enums.py:113:9 error[invalid-attribute-override] Invalid override of attribute `__name__`: class variable cannot override instance variable `type.__name__`

django-stubs (https://github.com/typeddjango/django-stubs)
+ tests/assert_type/db/migrations/test_classvar.py:18:5 error[invalid-attribute-override] Invalid override of attribute `operations`: instance variable cannot override class variable `Migration.operations`
+ tests/assert_type/db/migrations/test_classvar.py:19:5 error[invalid-attribute-override] Invalid override of attribute `initial`: instance variable cannot override class variable `Migration.initial`

pip (https://github.com/pypa/pip)
+ src/pip/_vendor/urllib3/connection.py:107:5 error[invalid-attribute-override] Invalid override of attribute `default_port`: class variable cannot override instance variable `HTTPConnection.default_port`

prefect (https://github.com/PrefectHQ/prefect)
+ src/integrations/prefect-ray/prefect_ray/context.py:21:5 error[invalid-attribute-override] Invalid override of attribute `__var__`: instance variable cannot override class variable `ContextModel.__var__`

scipy-stubs (https://github.com/scipy/scipy-stubs)
+ scipy-stubs/stats/_resampling.pyi:75:5 error[invalid-attribute-override] Invalid override of attribute `__match_args__`: class variable cannot override instance variable `ResamplingMethod.__match_args__`
+ scipy-stubs/stats/_resampling.pyi:121:5 error[invalid-attribute-override] Invalid override of attribute `__match_args__`: class variable cannot override instance variable `ResamplingMethod.__match_args__`

sphinx (https://github.com/sphinx-doc/sphinx)
+ sphinx/directives/__init__.py:55:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/__init__.py:360:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/admonitions.py:30:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `BaseAdmonition.option_spec`
+ sphinx/directives/admonitions.py:31:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `BaseAdmonition.option_spec`
+ sphinx/domains/changeset.py:62:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/index.py:71:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/ifconfig.py:44:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/todo.py:105:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/transforms/post_transforms/__init__.py:65:5 error[invalid-attribute-override] Invalid override of attribute `default_priority`: class variable cannot override instance variable `Transform.default_priority`
+ sphinx/directives/code.py:41:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/code.py:108:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/code.py:423:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/other.py:194:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/other.py:226:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/other.py:242:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/other.py:263:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/other.py:283:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/other.py:318:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/patches.py:92:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/directives/patches.py:142:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/c/__init__.py:421:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/c/__init__.py:451:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/c/__init__.py:480:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/cpp/__init__.py:542:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/cpp/__init__.py:573:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/cpp/__init__.py:603:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/javascript.py:335:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/python/__init__.py:480:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/python/__init__.py:548:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/std/__init__.py:197:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/std/__init__.py:340:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/std/__init__.py:419:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/domains/std/__init__.py:599:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/autosummary/__init__.py:202:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/doctest.py:151:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/doctest.py:157:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/doctest.py:163:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/doctest.py:174:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/doctest.py:184:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/graphviz.py:121:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/graphviz.py:201:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/ext/inheritance_diagram.py:398:5 error[invalid-attribute-override] Invalid override of attribute `option_spec`: class variable cannot override instance variable `Directive.option_spec`
+ sphinx/transforms/__init__.py:368:5 error[invalid-attribute-override] Invalid override of attribute `smartquotes_action`: class variable cannot override instance variable `SmartQuotes.smartquotes_action`
+ sphinx/transforms/post_transforms/code.py:38:5 error[invalid-attribute-override] Invalid override of attribute `default_priority`: class variable cannot override instance variable `Transform.default_priority`

urllib3 (https://github.com/urllib3/urllib3)
+ src/urllib3/connection.py:107:5 error[invalid-attribute-override] Invalid override of attribute `default_port`: class variable cannot override instance variable `HTTPConnection.default_port`

Full report with detailed diff (timing results)

codspeed-hq · 2026-04-21T13:53:41Z

Merging this PR will not alter performance

✅ 53 untouched benchmarks
⏩ 60 skipped benchmarks¹

_{Comparing charlie/attr-override (1d8c3fe) with main (810cab3)}

60 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

charliermarsh · 2026-04-21T15:05:10Z

The ecosystem changes are all true positives or cases that already have type ignores for other type-checkers.

AlexWaygood

We shouldn't use the invalid-method-override rule code for overrides of things that aren't methods. I deliberately gave that rule quite a specific name so that other kinds of overrides could have dedicated error codes with dedicated documentation pages, so it would be easy for users to find more explanation of why certain kinds of overrides are unsound

charliermarsh · 2026-04-21T17:34:05Z

Aye aye boss

Requested changes were made

astral-sh-bot Bot added the ty Multi-file analysis & type inference label Apr 21, 2026

charliermarsh force-pushed the charlie/attr-override branch from 413dc92 to d236787 Compare April 21, 2026 14:40

charliermarsh force-pushed the charlie/attr-override branch 2 times, most recently from 096ace5 to 2684664 Compare April 21, 2026 16:32

charliermarsh marked this pull request as ready for review April 21, 2026 16:39

charliermarsh requested review from AlexWaygood, carljm, dcreager, ibraheemdev and sharkdp as code owners April 21, 2026 16:39

astral-sh-bot Bot assigned sharkdp Apr 21, 2026

charliermarsh force-pushed the charlie/attr-override branch 2 times, most recently from b28ed78 to e6842c3 Compare April 21, 2026 16:47

AlexWaygood previously requested changes Apr 21, 2026

View reviewed changes

charliermarsh requested a review from MichaReiser as a code owner April 21, 2026 17:43

charliermarsh marked this pull request as draft April 21, 2026 17:49

charliermarsh marked this pull request as ready for review April 21, 2026 18:05

charliermarsh requested a review from AlexWaygood April 21, 2026 18:05

charliermarsh added 6 commits April 21, 2026 17:47

[ty] Detect invalid attribute overrides

8105b74

Fix

e95cef0

Tweaks

ee36036

Treat unannotated differently

ecd8df6

Allow inheritance

744b944

Simplify

98cca01

charliermarsh added 2 commits April 21, 2026 17:47

Use a dedicated diagnostic code

00598f0

Also augmented assignment

1d8c3fe

charliermarsh force-pushed the charlie/attr-override branch from a05fec7 to 1d8c3fe Compare April 21, 2026 21:47

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[ty] Detect invalid attribute overrides#24767

[ty] Detect invalid attribute overrides#24767
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Typing conformance results improved 🎉

Summary

Test file breakdown

True positives added (2)

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Memory usage report

Summary

Significant changes

sphinx

prefect

flake8

trio

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ecosystem-analyzer results

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Merging this PR will not alter performance

Footnotes

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`ecosystem-analyzer` results

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