In type_check_only function flush_errors parameter should be optional

[derlih]

In PR #4396 flush_errors parameter was added to type_check_only function from main.py:

def type_check_only(sources: List[BuildSource], bin_dir: Optional[str], options: Options, flush_errors: Optional[Callable[[List[str], bool], None]]) -> BuildResult:

But flush_errors parameter doesn't have the default value (I assume it should be None).

[gvanrossum]

You're right, the `Optional[]` is unnecessary. Maybe you can submit a PR to delete it?

…

On Tue, Mar 6, 2018 at 1:43 AM, Dmitriy Erlih ***@***.***> wrote: In PR #4396 <#4396> flush_errors parameter was added to type_check_only function from main.py: def type_check_only(sources: List[BuildSource], bin_dir: Optional[str], options: Options, flush_errors: Optional[Callable[[List[str], bool], None]]) -> BuildResult: But flush_errors parameter doesn't have the default value (I assume it should be None). — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4681>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACwrMkBUa5HIjUDvQiroh-rWFAGTZcRNks5tbloygaJpZM4SeZDU> .

-- --Guido van Rossum (python.org/~guido)

[emmatyping]

So in realpython/pytest-mypy#6, it seems pytest-mypy broke because of the new argument to type_check_only. pytest-mypy was using an internal undocumented API that we make no stability guarantees on.

Also it is valid to pass None as an argument for flush_errors, so I don't think there is anything that needs to be done in mypy. I think this can be closed.

[gvanrossum]

I think we should strongly discourage such use of interfaces internal to mypy. The only public APIs are the command line and the mypy.api module.