feat: Add ty as a linter #665

whoahbot · 2025-11-29T21:03:56Z

Adds ty as a linter for Python.

This is my first contribution here, so a lot of this is copied from the implementation for ruff, including the strategy for mirroring ty releases.

Changes are visible to end-users: yes

Searched for relevant documentation and updated as needed: yes
Breaking change (forces users to change their own code or config): no
Suggested release notes appear below: no

Test plan

New test cases added

Added unsupported_operator.py as an example lint, and call_non_callable.py , which should be ignored by the ty.toml configuration file.

CLAassistant · 2025-11-29T21:04:05Z

All committers have signed the CLA.

aspect-workflows · 2025-11-29T21:07:20Z

Test

All tests were cache hits

5 tests (100.0%) were fully cached saving 2s.

Test

example

8 test targets passed

Targets

//tools/format:format_test_HTML_Jinja_with_djlint [k8-fastbuild]4s
//tools/format:format_test_JavaScript_with_prettier [k8-fastbuild]15s
//tools/format:format_test_Markdown_with_prettier [k8-fastbuild]2s
//tools/format:format_test_Protocol_Buffer_with_buf [k8-fastbuild]1s
//tools/format:format_test_Python_with_ruff [k8-fastbuild]420ms
//tools/format:format_test_SQL_with_prettier [k8-fastbuild]3s
//tools/format:format_test_Scala_with_scalafmt [k8-fastbuild]8s
//tools/format:format_test_Starlark_with_buildifier [k8-fastbuild]285ms

Total test execution time was 34s. 35 tests (81.4%) were fully cached saving 14s.

Test (WORKSPACE) (Test)

example

8 test targets passed

Targets

//tools/format:format_test_HTML_Jinja_with_djlint [k8-fastbuild]2s
//tools/format:format_test_JavaScript_with_prettier [k8-fastbuild]5s
//tools/format:format_test_Markdown_with_prettier [k8-fastbuild]910ms
//tools/format:format_test_Protocol_Buffer_with_buf [k8-fastbuild]722ms
//tools/format:format_test_Python_with_ruff [k8-fastbuild]213ms
//tools/format:format_test_SQL_with_prettier [k8-fastbuild]1s
//tools/format:format_test_Scala_with_scalafmt [k8-fastbuild]3s
//tools/format:format_test_Starlark_with_buildifier [k8-fastbuild]241ms

Total test execution time was 14s. 13 tests (61.9%) were fully cached saving 8s.

alexeagle

awesome, excited that you've broken ground on this.

We'll have to do some README edits before landing to warn about both ty immaturity and also the experimental nature of this linter aspect.

alexeagle · 2025-12-02T17:11:51Z

.github/workflows/mirror.yml

          npx @bazel/buildifier lint/ruff_versions.bzl
+      - name: Update ty
+        run: |
+          ./lint/mirror_ty.sh


it's possible that we skip the mirroring, now that many Bazel users check in their MODULE.bazel.lock file they can get the Trust-on-first-use guarantee. I suspect it's too soon to change that, just raising for our team to consider

for now do you mind dropping this file and the mirror_ty.sh from this PR? since it comes in through rules_multitool there are other options for updating it

alexeagle · 2025-12-02T17:12:33Z

example/src/call_non_callable.py

@@ -0,0 +1,5 @@
+# Demo with just running ty:


this demo should look like bazel run @some_label//:ty -- some_file.py - we want to convince ourselves we know how to call the tool standalone

alexeagle · 2025-12-02T17:13:38Z

example/test/unsupported_operator.py

@@ -0,0 +1,3 @@
+# Demo with just running ty:
+# $ bazel run --run_under="cd $PWD &&" -- //tools/lint:ty check --config=ty.toml src/*.py


alexeagle · 2025-12-02T17:15:49Z

lint/ty.bzl

+load("@aspect_rules_lint//lint:ty.bzl", "lint_ty_aspect")
+
+ty = lint_ty_aspect(
+    binary = Label("@aspect_rules_lint//lint:ty_bin",


nit: missing a closing paren

alexeagle · 2025-12-02T17:16:10Z

lint/ty.bzl

+```starlark
+# Note: this won't interact properly with the --platform flag, see
+# https://github.com/aspect-build/rules_lint/issues/389
+alias(


I think this is copy-pasta? They should get this for free from multitool

alexeagle · 2025-12-02T17:17:38Z

lint/ty.bzl

+            https://docs.astral.sh/ty/reference/exit-codes/
+        env: environment variables for ty
+    """
+    inputs = srcs + config


The big remaining work here is a graph of py_library(name="a", deps = ["b"]) -> py_library(name="b")

I think you'll already find that it's broken to lint a because it will be missing type definitions from b.
In fixing that, we want to avoid any work of type-checking the b sources a second time.

Thanks for pointing that out. I'll start looking into this.

@alexeagle After looking into this a bit I had some directional questions that I'd like to get your input on.

It seems like the flake8 implementation is trying to avoid taking a dependency on rules_python, but using the PyInfo provider would be one way to collect the dependencies of a target. What are your thoughts on taking a dependency on rules_python?

I was also looking at the implementation of rules_mypy which I think handles some other cases I think this linter might want to eventually cover. Any thoughts on the approach taken in rules_mypy that would be good to pattern after or avoid?

Thanks!

I think it's unavoidable to need the PyInfo symbol so rules_python is a required dep. bazelbuild/bazel#25509 can make it less painful.

@arrdem has spent more time in rules_mypy recently than I have. Could you give any short specifics or links on which cases/approach you're looking at?

lint/ty.bzl

- Removed ty mirroring in favor of multitool usage - Fixed running example ty linting with a standalone command. - Fixed a closing paren in the docs. - Dropped `fetch_ty` helper.

whoahbot changed the title ~~Feat: Add ty as a linter~~ feat: Add ty as a linter Nov 29, 2025

whoahbot force-pushed the add_ty branch 2 times, most recently from 95be6f4 to 70b0499 Compare November 29, 2025 23:16

feat: Add ty as a linter

453e974

whoahbot force-pushed the add_ty branch from 70b0499 to 453e974 Compare November 30, 2025 00:45

Merge branch 'main' into add_ty

9b3e4cf

alexeagle requested review from alexeagle and arrdem December 2, 2025 16:14

alexeagle reviewed Dec 2, 2025

View reviewed changes

whoahbot added 3 commits December 3, 2025 01:28

Address PR comments

239f4cb

- Removed ty mirroring in favor of multitool usage - Fixed running example ty linting with a standalone command. - Fixed a closing paren in the docs. - Dropped `fetch_ty` helper.

WIP: Add transitive dependency support to ty

08bd80a

WIP: Use PyInfo to collect transitive deps

c6f2f9a

whoahbot force-pushed the add_ty branch 2 times, most recently from 13ac733 to 719652b Compare December 5, 2025 22:54

WIP: Support third party dependencies when linting.

06ebc05

whoahbot force-pushed the add_ty branch from 719652b to 06ebc05 Compare December 6, 2025 17:07

		@@ -0,0 +1,3 @@
		# Demo with just running ty:
		# $ bazel run --run_under="cd $PWD &&" -- //tools/lint:ty check --config=ty.toml src/*.py

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whoahbot commented Nov 29, 2025

Changes are visible to end-users: yes

Test plan

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CLAassistant commented Nov 29, 2025 •

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aspect-workflows bot commented Nov 29, 2025 •

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