[jsgf]

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).