Derivation file not found: Old version <version>" not present in <branch>

[henrirosten]

While manually updating libidn2, I notice nixpkgs-update failed with message:

Old version 2.3.2" not present in master derivation file with contents ...

I believe this occurs due to nix edit libidn2 -f . not finding the derivation file for libidn2. I see this issue is also mentioned in the FAQ.

Eyeing the nixpkgs-update logs, I see at least some other instances of this same issue for other packages too.

Would it be possible to change the nixpkgs-update to fallback to running a find with appropriate search terms when nix edit fails to find the derivation for the target package? Something like:

# In nixpkgs root dir
find ./pkgs -type f -ipath "*/libidn2/default.nix" -print -quit

If that, too, fails to find a derivation with matching old version, then error-out with a proper error message.

[rhendric]

Why does nix edit fail for libidn2?

I'm under the impression that most of the time when we see this sort of error, it's because the version number is stored in a file that doesn't look like */$pname/default.nix. nix edit, as far as I was aware, will pull up the file in which the meta.description attribute is set. It surprises me that this doesn't happen for this library.