The warnings about MacOS are mostly being cautious, as I don't think anyone actually runs it in production.

I work with open source Hack code a lot, and I almost always use the MacOS binaries instead of Linux for development.

For my workflows, it's more that there's two major missing things - I'm not seeing random issues. The big things are:

- a lot of the profiling features are Linux-only

- the mcrouter extension is Linux-only. If you're using memcached, this extension is useful even without mcrouterd, as it provides a true async (Awaitable) client.

To clarify, xhp-js was not server-side rendering - it's a framework for generating javascript code, and getting an DOM element ID for a react element that the hack code can refer to and use elsewhere, e.g. by passing to some other generated JS.

> Are there any large Hack codebases I can explore?

depends what you mean by 'large' - perhaps https://github.com/hhvm/user-documentation ?

> Does anyone know if FB tracks changes to PHP so Hack is "up to date"?

No, for the most part, Hack no longer considers PHP 'upstream'. Exceptions are things like security fixes to extension functions, if that particular extension function was derived from PHP.

Facebook doesn't. Open source users of Hack do, and it uses packagist.org - however if a package is written in PHP, Hack code can't use it.

Not 100% accurate, but if a package's composer.json does not require HHVM, it will most likely install into a hack project, but be unusable.

There's also https://github.com/hhvm/hack-codegen/tree/master/examples/do..., along with the article at https://engineering.fb.com/2015/08/20/open-source/writing-co...

This is modern Hack code, but not representative of the state of the Ent framework nowadays - ent/ent is closer design-wise, but not usable from Hack.

> Now I also don't know if I buy that MAX_INT + 1 and pass-by-reference is a pressing enough use case to break compatibility. I'd be open to hearing why, but I'd be starting from a position of skepticism.

This is an example of a change that will be made, not a rationale for the decision.

https://github.com/hhvm/hack-router/ and https://github.com/hhvm/hack-router-codegen/ power docs.hhvm.com and some of our other users; they do have problems such as extremely lacking documentation, which I'm going to be addressing soon.

This is definitely an area we're planning on working on - and this post is meant to be announcing the start of this work, not that it's ready :)

For completeness: Sara Golemon started porting Facebook's old PHP5 implementation of XHP to PHP7 - you can find it here: https://github.com/phplang/xhp + https://github.com/phplang/xhp-lib

we're currently leaning towards out/inout parameters, with copy semantics, not byref (and in most cases, we'll probably be able to optimize away the copy); not certain yet though.

Would be nice to hear what comes out of it and how it works!

You'll also see a few of these on http://php.net/manual/en/migration70.incompatible.php :p