Cormac Relf

Ah, I think I see what's going on. `allow_cache_upload` is getting slowly rolled out to more rules as the responsible team becomes sure they've dealt with the issues. https://github.com/facebook/buck2/commit/211d555e71aa80f78cd037c8580e99a20a8990d6

Outside of an RE-majority context, choosing to allow cache uploads seems to be more a function of the hermeticity of toolchains, rather than something you'd want to be forced to...

https://github.com/facebook/buck2/blob/80d61ff8dc71485d9c56600ccf6927aeed10489f/app/buck2_execute_impl/src/executors/caching.rs#L292-L374 ~~It is building a vec of futures, one per node of the directory tree, and running `try_join_all` on all of them at once. I am guessing it never manages...

Ah, in that case https://github.com/facebook/buck2/blob/80d61ff8dc71485d9c56600ccf6927aeed10489f/remote_execution/oss/re_grpc/src/client.rs#L1117-L1139 The uploads may be chunked into `max_msg_size`, but all of the data is still read in one go, producing a vec of upload requests, each...

Any attrs.source() can accept either a file, or a target that provides a DefaultInfo. DefaultInfo has a default_outputs field, and that's a plural; it's a list. So I wonder if...

Alas, apparently not. This gives "Expected a single artifact from root//scratch:id (platforms//:host#9f5b0576f0e10a13), but it returned 2 artifacts". I question what the point of `default_outputs` is if not for exactly this...

I can't see a way to get genrule to do it. Then again I have almost never seen fit to use genrule -- it is just not very good at...

Yes, technically you can write a file that lists other files, and then is passed as an arg file to the cxx compiler via `compiler_flags = ["@$(location :gen)"]` can make...

I think it boils down to the words themselves: - Approximate is an approximation, a guess. You don't know exactly when it was but you estimate that it was X....

If anything "circa" should be for approximation, not uncertainty.