Buck2: Our open source build system

I feel so lucky that I found waf[1] a few years ago. It just... solves everything. Build systems are notoriously difficult to get right, but waf is about as close to perfect as you can get. Even when it doesn't do something you need, or it does things in a way that doesn't work for you, the amount of work needed to extend/modify/optimize it to your project's needs is tiny (minus the learning curve ofc, but the core is <10k lines of Python with zero dependencies), and doesn't require you to maintain a fork or anything like that.

The fact that the Buck team felt they had to do a from scratch rewrite to build the features they needed just goes to show how hard it is to design something robust in this area.

If there are any people in the Buck team here, I would be curious to hear if you all happened to evaluate waf before choosing to build Buck? I know FB's scale makes their needs unique, but at least at a surface level, it doesn't seem like Buck offers anything that couldn't have been implemented easily in waf. Adding Starlark, optimizing performance, implementing remote task execution, adding fancy console output, implementing hermetic builds, supporting any language, etc...

[1]: https://waf.io/

I don't know if they considered waf specifically, but the team is definitely very familiar with the state of the art: https://www.microsoft.com/en-us/research/uploads/prod/2018/0...

One of the key requirements is that Buck2 had to be an (almost) drop-in replacement for Buck1 since there's no way we could reasonably rewrite all the millions of existing build rules to accommodate anything else.

Also Buck needs to support aggressive caching, and doing that reliably puts lots of other constraints on the build system (eg deterministic build actions via strong hermeticity) which lots of build systems don't really support. It's not clear to me whether waf does, for example (though if you squint it does look a bit like Buck's rule definitions in Starlark).