Hi, there is a slight problem with this change - self.get_job has a different return type to this function. It can return LoadJob, etc as well as the QueryJob we're expecting so the actual return type doesn't match what is declared for this function.

I don't understand the situations that could result in this code being called, but presumably in reality this would always be a QueryJob? Unfortunately this is causing me problems when running pylint over some code that calls this, because it thinks the function can return LoadJob, and that has a different set of members to QueryJob.

Many thanks,
Andrew Wilkinson

Indeed, in this contextself.get_job() returns aQueryJob, becausejob_id is the same ID that was used a few lines above when constructing a new query job (and then starting it).

This project usespytype for static type checks and it did not complain, but apparentlypylint could not deduce the same and reported a false issue.

Could you tellpylint to ignore return type in that specific line wherequery() is called? IMHO that justifiable, becausepylint is wrong there.

Having looked into this a bit further I agree that pylint is wrong. It's a bit of a pain to have disable this check every time we call query, but I think this is a sign that pylint is aging and not keeping up with modern Python's type syntax.

Sorry for the noise.

Cheers,
Andrew

No worries, it was a perfectly valid comment.

Ideally,pylint would allow ignoring particular warnings for lines matching a regex, but I'm not sure if that's currently supported? It would make disabling those false positives much cleaner compared to spamming the# pylint: disable=... comments all around the code.

Sadly the error isn't raised on the call toquery, but when you try and use the return value. In my case this is accessingnum_dml_affected_rows, which only exists onQueryJob, and not onLoadJob. Even if it did support disabling errors using a regex, I'm not sure it would be practical to create one.

It's been bugging me why this wouldn't be picked up by the type checker. I think I've tracked it down to the fact thatLoadJob,QueryJob, etc all derive from_AsyncJob, which in turn derives fromgoogle.api_core.future.polling.PollingFuture. The problem is thatgoogle.api_core.future.polling.PollingFuture is not typable, so it gets turns into anAny type, which makes all the job types equivalent and therefore doesn't generate an error. When testing with mypy you have to add# type: ignore to thePollingFuture import line explicitly, but I guesspytype is more forgiving.

I've create the attached file demonstrating the problem (annoyingly github won't let me attach the file as a .py). As currently written it'll generate an error in both mypy and pytype, but swap the comments on lines 5 and 6 and the error goes away.

Anyway, I have a reasonable workaround, so if you want to leave this that's absolutely fine. If in future thepython-api-core library adds typing then I expect this to break though. Adding anassert isinstance(query_job, job.QueryJob) will resolve the issue.

Cheers,
Andrew
invalid_return_union.txt