Respect JSON output mode for syntax errors

[AA-Turner]

Fixes #21370.

A

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[hauntsaninja]

Thanks!

[ilevkivskyi]

I think this will not work with parallel checking. You need to update build_worker/worker.py as well.

[AA-Turner]

@ilevkivskyi I think this was added in your earlier PR #21319. I might be missing something though, do you have a pointer where I should look?

A

[ilevkivskyi]

My PR simply brought the parallel checking to parity with what existed at the time in sequential mode. In particular, Errors() still needs the new argument in build_worker/worker.py.

To test this you will need a blocker error that happens at a later stage, for example:

$ echo break >bug.py
$ python -m mypy bug.py --output=json --num-workers=4
bug.py:1: error: "break" outside loop
Found 1 error in 1 file (errors prevented further checking)

(Also to write a unit test for this you will need to update test/testoutput.py, since currently it actually ignores the # flags: directive)

[AA-Turner]

Thanks @ilevkivskyi, opened #21434.

A