Mypy improvements

[Tinche]

Not to be merged yet.

The problem is the Mypy plugin doesn't return a namedtuple, but an ordinary tuple. We should fix this in the Mypy plugin.

[hynek]

Is this something that should remain open?

[Tinche]

Yeah, we need to merge this when Mypy release 0.940 I believe.

[hynek]

Maybe we should get it to pass CI until then. 😇

[Tinche]

I can't until Mypy releases :p

[hynek]

eg ok, your phrasing sounded like it's needed, once mypy is out

[Tinche]

It's just more sophisticated type stubs, we don't have to match their release exactly. But we might want to.

[hkclark]

@Tinche I noticed recently that using attrs 21.4.0 and the new attrs namespace didn't seem to be supported by mypy. I was initially thinking this PR might add it, but in taking a quick look at the changes, it doesn't seem so (but I'm not expert on mypy type syntax). I was just curious if there was a plan to get support for the attrs namespace or if I was just doing something wrong on my end. :-) Thanks for your work on this!

[hynek]

I noticed recently that using attrs 21.4.0 and the new attrs namespace didn't seem to be supported by mypy.

The new attrs namespace is absolutely supported by mypy. I use it all the time.

We've achieved it by re-importing symbols from the attr namespace and mypy can resolve that.

[hkclark]

I noticed recently that using attrs 21.4.0 and the new attrs namespace didn't seem to be supported by mypy.

The new attrs namespace is absolutely supported by mypy. I use it all the time.

We've achieved it by re-importing symbols from the attr namespace and mypy can resolve that.

Hmm, OK, thanks for the info! I guess let me convert this project at work back to the attrs namespace and see if I can figure out what's going on. :-)

While I have you, I assume it's expected that mypy cannot handle "fancy converters" -- I get error: Unsupported converter, only named functions and types are currently supported if I do things like: a) converter=lambda value: weakref.proxy(value) or converter=[...] or converter=attrs.validtors.pipe(...).

[hkclark]

@hynek To follow up on the issues I mentioned in this project I'm working on, when I use the attrs namespace for everything I get this from mypy for my converters:

error: Module has no attribute "converters"  [attr-defined]

[hynek]

Unfortunately, mypy support for converters is very bare-bones. There's not much we can do about it. Your error must have some other cause. It's explicitly tested here:

attrs/tests/typing_example.py

Line 414 in 7804a68

from attrs.converters import optional

[hkclark]

Unfortunately, mypy support for converters is very bare-bones. There's not much we can do about it. Your error must have some other cause. It's explicitly tested here:

attrs/tests/typing_example.py

Line 414 in 7804a68

from attrs.converters import optional

@hynek OK, thank you. I'll study it more and if I can't find a cause on my side, I'll try to open a ticket with very bare-bones example code that recreates it. And maybe I'll open a PR that adds a comment to the docs re converters being limited just so others know about the limitations. Thank you again!

[Tinche]

@hynek this should go in now. I guess I need to rebase though.

[hynek]

@hkclark turns out you were right and our tests broken: #930 + #931

Sorry for that!

[hynek]

@Tinche this is breaking even on 3.6…wanna wait until this stuff is fixed in mypy? :-/

[hkclark]

@hkclark turns out you were right and our tests broken: #930 + #931

Sorry for that!

@hynek No problem at all. Thanks for getting back to me. I'm just glad to know I wasn't going totally crazy. :-) Thank you again for your work on attrs... I really like it and look forward to ongoing new features.

[Tinche]

Mergy mergy now?

[hynek]

Allmost all of CI redy redy?

[hynek]

• why does test_mypy hate us, personally?
• it should be something like "AttrsClassInstance" or "AttrsInstance" for all I care?