Parallel compiler and mix dependencies

[jeroenvisser101]

@hauleth

Due to expressiveness of Elixir the parallel compilation of different projects at once can go south enormously fast.

It could even be an opt-in feature, allowing you to execute mix deps.compile --parallel, and as we find cases that cause problems, we can tackle them. After some time, it could become the default with a flag to disable.

@tristan

I’ve wanted to introduce this in rebar3 from the beginning but never got around to it. We have a big rework of the compiler in the works and hope it can be introduced then

Looks very promising!

@dimitarvp

True true. I didn’t account for all possibilities. A manual switch in the package itself ( has_nif: true for example?) could also help. Can’t imagine it being that hard to introduce and default to false if not present. As mentioned above, might make several NIF packages fight for your CPU cores but eh, is that a doomsday scenario?

Or compile_parallel: false to disable, or as I mentioned, allow package authors to specify if it supports being compiled in parallel with others. Additionally, like extra_applications, you could specify a allow/block-list to override parallel compiler compatibility.