Hello guys. I have been recently looking into ways for improving dub and I've find something which could make it get a lot faster for building the projects and the idea is fairly simple: It is possible to parallelize its dependencies build commands almost completely. No need to wait for the requirements to finish first.

All this process could be done in a single go, concurrently, and the only time it need to wait for the other to finish is in the link process.

So instead of doing:

A->[B -> C] -> [D -> E] -> Link

We could basically do

[A, B, C, D, E] -> Link

The reason for that is: for building the libraries all the import paths are basically reparsed anyway, so they don't actually depend on each other, the requirements could be solved upfront by simply saving the version statements in each build.

I would like to get this stuff working ASAP, here is the issue for that: https://github.com/dlang/dub/issues/2702

I started working on that but unfortunately my time is really short so any help is appreciated.

The main problem right now is basically making dub less statefull (a little hard since it uses classes and intermediate state everywhere). The thing is that I know this isn't too hard to make it happen.

If someone is worried about the pre/postBuildCommands, we could just get this stuff done firstly and use the existing --parallel build flag which only works together with the --single flag and then it could be fixed later since this has a massive improvement potential with almost no work.