use of meta.tests causes evaluation errors

[peti]

#44439 adds meta.tests to dovecot, but that attribute is not supported by Nix and causes evaluation errors, i.e.:

$ nix-env -qaP --meta --json  >/dev/null
derivation 'dovecot-2.3.3' has invalid meta attribute 'tests'
derivation 'opensmtpd-6.4.0p1' has invalid meta attribute 'tests'

This output breaks several scripts of mine (for updating the Haskell package set) and I would kindly request to make those warnings disappear one way or another.

Ping: @Ekleog, @timokau

[timokau]

This is weird since @Ekleog did add the tests attribute to metaTypes in pkgs/stdenv/generic/check-meta.nix.

[grahamc]

My guess is a derivations' meta can't contain derivations, but I'm not sure. I think this may be true because it raises this question: when evaluating and querying meta fields about a package (which is possible,) should the derivations be built or not? Yes, for consistency it should, but running a bunch of tests when querying packages doesn't make sense.

[Ekleog]

@timokau It appears to be also checked a second time in nix itself for some (but not all) operations: https://github.com/NixOS/nix/blob/f6a3dfe4e06980b2d060fd1a646cb5ca20f29779/src/nix-env/nix-env.cc#L872

This means either we need to change nix, or we need to use passthru. I'm opening an issue on nix for more thought on this.

[grahamc]

Probably should just use passthru.

[Ekleog]

OK, I'll include the switch to passthru in the refactoring I'm doing to address the cross-building issues.

[Ekleog]

This should be fixed in #50233

[timokau]

Checking this in nix itself seems out of place to me, but using patthru is probably the best quick fix.

[Ekleog]

Feel free to react to NixOS/nix#2532, which I opened as the issue seen from the nix point of view :)