Add threshold flag for mypy errors

[rahulpal75]

Feature
Currently mypy has flags to disable error based on the error codes. But There is no such options to add threshold for number of errors.
I came across --max-error-count but this option is not working in python 3.9.
Hence i am requesting to add some flag similar to --max-error-count which will throw error if the number of error count exceed the given value.

Pitch

There are many teams which has not on-boarded to mypy . And if someone try to onboard, then that team either has to fix all the errors or ignore the error. But by adding this feature team can onboard to mypy and can fix the error incrementally by controlling the threshold value.

[A5rocks]

In the meanwhile, teams can always use an extra script to filter mypy's output.

That doesn't detract from this feature request though.

[rahulpal75]

In the meanwhile, teams can always use an extra script to filter mypy's output.

That doesn't detract from this feature request though.

Can you please share some example of doing this.

[A5rocks]

In the meanwhile, teams can always use an extra script to filter mypy's output.

That doesn't detract from this feature request though.

Can you please share some example of doing this.

I don't have any specific examples but https://github.com/python-trio/trio/blob/main/src/trio/_tools/mypy_annotate.py translates mypy's output to GitHub annotations. It wouldn't take much time to modify it to count the number of a certain error and only return an error if it's too high.

[hauntsaninja]

You can use --output json to write your own script.

I think a raw number isn't really a good approach, it's too finnicky (sometimes adding better types will cause a bunch of new errors), so I don't think we should add this to mypy.

See the advice in https://mypy.readthedocs.io/en/stable/existing_code.html , particularly about per-module configuration. You can also google "mypy baseline" for tools people have to make allowlisting existing errors easier.