@Ericson2314, thanks for your PR! By analyzing the history of the files in this pull request, we identified @edolstra, @domenkozar and @rbvermaa to be potential reviewers.

http://hydra.nixos.org/eval/1317573 The good news is I didn't break any existing jobs, the bad news is that my assert ...; trues are not considered jobs.

Ah, I guess it has to be assert ...; someTrivialJob. But I don't really know how Hydra works.

Those assertions should be failing, so I figured Hydra would have no idea whether there is a derivation behind them. Maybe it has some magic, but in any event I don't want the job to dissapear if the assert isn't thrown. I'll try something like if .... then "passing-job" runCommand {} "touch $out" else runCommand "failing-job" {} "false"

FWIW they do show up in http://hydra.nixos.org/jobset/nixpkgs/cross-trunk#tabs-errors. But yes, you do need some sort of dummy derivations so they show up like the others.

Oh, that's a good start. It's weird that that tab is there with all the evaluations, rather than per-evaluation.

From this PR:

Converting to a string (drv path) before checking equality is probably a
good idea lest there be some irrelevant pass-through debug attrs that
cause false negatives.

Equality comparison of derivations seems to be special and different from equality comparison of a normal set. When you make the changes necessary to get those tests to pass, it proves that a derivation with a crossDrv inside it (for foosys and foolibc) can be equal to a derivation without a crossDrv. So I bet that debugging attributes also don't matter.