idea: add a toggle so that pyright ignores narrowed mypy type:ignore annotations

[danielbprice]

I recently reviewed the open issues and forum discussions about the issues over the interpretation of type: ignore comments. I maintain a source base where Pyright is the primary type checker but at times we also run mypy to see if it finds anything else.

A typical example from our source code would be:

# The azure code post-processes this attribute into the exception, so pyright doesn't know about it.
error_code = e.error_code  # pyright: ignore[reportAttributeAccessIssue]

mypy also finds and surfaces this non-issue. I could simply add type: ignore to silence both checkers but as a long time user of lint and other checking tools, I feel strongly that the best practice is to silence just the specific error; this also helps the code be more self-documenting.

The issues here stem from mypy's non-standard extension # type: ignore[specific-issue]. This is discussed here: python/mypy#12358 and elsewhere. I can't add # type: ignore[something-specific-to-mypy] without pyright treating this as # type: ignore (suppress all issues). mypy is (dubiously) extending the spec, and pyright is trying to adhere to the spec as written.

After reviewing the differences of opinion between the various parties, I wondered if Pyright could bend slightly here, and add a small configuration knob to say: if I see a narrowed mypy # type: ignore[something] statement, instead of treating it as a valid PEP484 comment, treat it as invalid. And drop it on the floor. Then it would be possible to have:

error_code = e.error_code  # type: ignore[attr-defined] # pyright: ignore[reportAttributeAccessIssue]
                               ^ pyright sees this as         ^ mypy ignores this
                                 mypy PEP-non-compliant
                                 and ignores

A user who opts to stick type: ignore here, without the mypy-specific narrowing, would have things work as before. Something like ignore_mypy_extended_type_ignores = true (uhh, naming is hard).

I realize that this request is putting the onus on Pyright to solve a problem caused by mypy, but I didn't see this suggestion in the previous discussions, and I thought it might provide an escape hatch for everyone who is affected until such time as mypy implements mypy: comments or a new PEP with further clarifications is produced.

Thanks. One way or another, I really appreciate this tool!

[erictraut]

Pyright provides a setting enableTypeIgnoreComments. If you set this to false, it will treat all # type: ignore comments as no-ops. This doesn't affect # pyright: ignore statements. I think that's effectively what you're asking for here.

[danielbprice]

Thank you-- I think that will do the trick!