Should be able to generate spidermonkey bindings without downstream patches

[fitzgen]

Right now, servo/mozjs has a bunch of downstream patches that simplify and dumb down spidermonkey headers and even completely hide various types.

We should get to the point where we don't need these downstream patches, and can run bindgen in CI for mozilla-central. That doesn't necessarily mean that we have to generate bindings for all of C++, but maybe have some configuration of things to ignore rather than manually ifdef away chunks of code.

Blocks https://bugzilla.mozilla.org/show_bug.cgi?id=1277343

[emilio]

Actually we have a flag to ignore unknown types, I don't think that's the problem.

The problem is most likely that we generate bad bindings for some kind of C++. We have an extensive set of flags to ignore types, mark them as opaque, etc. That's probably enough, except in the case we generate a bad type that is absolutely necessary to rust-mozjs.

Nick, do you know what are the blockers here? I'm happy to help :)

[Ms2ger]

Once the current smup lands, I'll try to see if we can replace some of those ifdefs by bindgen flags.

[fitzgen]

Does bindgen support keeping those flags in some kind of configuration file? Something we can keep in m-c/js/src/bindgen-flags or something? I think that would make keeping C-I green easier for spidermonkey hackers who don't necessarily want to touch bindgen/rust stuff when adding new JSAPI things.

[fitzgen]

Nick, do you know what are the blockers here? I'm happy to help :)

Thanks! :-D

Not yet, I have a couple things to get done first (grrr NSPR) but I was going to start just running bindgen on m-c's js/ and filing bugs / submitting PRs for things that fail without downstream patches.

Wash, rinse, repeat until everything Just Works :)

[emilio]

Sounds good to me :-)
Regarding the bindgen-flags thing, I don't think something like that would be difficult to implement.

For comparison, now what we have in stylo, for example, is a python script that takes care of invoking bindgen appropriately, and it works fairly well.

[emilio]

This is fixed, isn't it?