cc @basvandijk in case the codeowners ping gets lost in the storm. :-)

Shouldn't this already be covered by preferLocalBuild? According to the manual:

If this attribute is set to true, it has two effects. First, the derivation will always be built, not substituted, even if a substitute is available. Second, if distributed building is enabled, then, if possible, the derivaton will be built locally instead of forwarded to a remote machine. This is appropriate for trivial builders where the cost of doing a download or remote build would exceed the cost of building locally.

@lheckemann The manual was misleading, but has been corrected: NixOS/nix@5a3f140 NixOS/nix@1109193

Aah, I see. Thanks!

Good change! Thank you

Is there a way to override this change easily?
Context: My team has a fairly big project and we a few forked dependencies and a few pinned dependencies. In all running callCabal2nix over and over again on them takes about 3 minutes in our CI. These would almost always be a cache hit for us.

@akshaymankar you can just override all your callCabal2nix with allowSubstitutes = true;, this could be done in a overlay, something like:

selfh: superh: {
    callCabal2nix = name: path: args: (superh.callCabal2nix name path args).overrideAttrs(_old: { allowSubstitutes = true; });
}

However, I'm curious you are raising this question right now. Maybe it is related to #194753 that I'm trying to merge now?

Thanks for the pointer, I ended up with this:

hself: hsuper: {
    haskellSrc2nix = args: (hsuper.haskellSrc2nix args).overrideAttrs(_old: {allowSubstitutes = true;});
}

But in all I gained almost no time for about 40 packages, so I removed it.

However, I'm curious you are raising this question right now. Maybe it is related to #194753 that I'm trying to merge now?

I never had to pin so many packages in any of my other projects, so I never even noticed that substitutes were not allowed for this derivation. So, it is not related.