[nascheme]

Summary

This allows the following comments at the beginning of files:

# pyrefly: ignore-errors[kind, ...]

Multiple kinds can be comma-separated on one line, or split across several ignore-errors lines; the lists accumulate.

My use case for this is that I'm gradually increasing pyrefly's strictness. I want to turn on errors like this:

implicit-any-parameter = "error"       # unannotated function parameters
implicit-any-type-argument = "error"   # bare `list` / `dict` (no type args)
implicit-any-empty-container = "error" # `x = []` with no annotation

However, I have many "legacy" Python files that don't conform to this level of strictness. Rather than have many "sub_config" sections or add individual per-line suppressions, I want to suppress these kinds of errors for whole files.

Test Plan

The feature is covered by integration tests in pyrefly/lib/test/suppression.rs, using the testcase! macro. Each test is a snippet of Python source with inline error expectations: a # E: <message> comment marks a line where an error is expected, and any line without such a comment must produce no error. The macro type-checks the snippet and asserts that emitted errors match the annotations exactly.

Three new tests exercise the # pyrefly: ignore-errors[kind, ...] syntax:

• test_pyrefly_top_level_ignore_specific_kind — suppresses a single kind (bad-assignment) and verifies that an unlisted kind (bad-return) still reports. The bad-assignment line has no # E:, while the return "oops" line carries a # E: annotation, proving suppression is kind-scoped rather than whole-file.
• test_pyrefly_top_level_ignore_specific_kinds_one_line — two kinds comma-separated in one comment ([bad-assignment, bad-return]); both errors are suppressed (no annotations).
• test_pyrefly_top_level_ignore_specific_kinds_multiline — the same two kinds split across two separate ignore-errors lines, verifying that the lists accumulate.

Together these cover the single-kind, comma-separated, and multi-line accumulation paths, and the negative case (an unlisted kind is not suppressed).

Running the tests

cargo test -p pyrefly suppression

Result: 78 passed, 0 failed (the full suppression suite, including the three new tests).

Note: Claude Opus 4.8 assisted with writing this PR.

[rchen152]

Sorry for the lack of review - looks like this PR slipped through the cracks. I'll take a look on Monday.

[meta-codesync]

@rchen152 has imported this pull request. If you are a Meta employee, you can view this in D115517177. (Because this pull request was imported automatically, there will not be any future comments.)

[rchen152]

Actually, this was already implemented in #3944.