Are you referring to the fact that pip appears to build such dependencies twice? Because if so, then again, we’ve already agreed that having pip reuse cached wheels here would be useful. And even if pip doesn’t do that at the moment, there’s a difference between “cannot install via wheels” and “is extremely slow due to building dependencies twice”.
If you’re referring to something different, then you’ve not managed to express the problem clearly yet, because even across about 3 different long threads, people are still not clear what it is that you’re insisting is currently “not quite possible”
Yes, I want to second this (not just clicking the “heart”). I think you (Jeroen) have already gotten the message across that this is an important issue, so I don’t think you need to state that further. Regarding your point on the other issue of saying “must,” I’m not sure the particular wording really matters because the bigger issue is finding someone to do the work (or doing it yourself) even if we agree it should be done. We can’t command volunteers to do work.
I probably really meant to say “their configuration”. I wanted to avoid starting up the “PEP 517 doesn’t support this because pip rebuilds dependencies” side issue. But apparently I failed
Note the difference to --no-binary :all:.
In that case, I expect that everything listed in pyproject.toml is downloaded per wheel and the project itself is build from source. Currently, the first step is just skipped.
Is there a work-around possible in which I tell pip to install everything listed in pyproject.toml? By that, I could at least write a "pip install build-dependencies; pip install --no-binary " two-liner to work around this.
@ax3l This is seems like maybe it belongs in a different thread, or possibly in an issue on the pip tracker? If I have kept track correctly, this thread is still about whether wheels are a necessary intermediate step for installation to pip, not about pre-built wheels or about what gets sourced from pre-built wheels.
I think you (Jeroen) have already gotten the message across that this is an important issue, so I don’t think you need to state that further. Regarding your point 
