[Nix-dev] Proposal: adding fetchapt support to nixpkgs

[Profpatsch]

On 16-10-25 04:42am, Chuan-kai Lin wrote:
> Adding support for fetching binary packages in Debian format from an APT
> repository would solve this problem.  I envision that a nixpkg would
> specify:
> - the APT repository base URL
> - the release name (e.g., stable, testing, or unstable),
> - the binary package name,
> - repository signing key (for repositories that implement secure APT,
> https://wiki.debian.org/SecureApt).
> 
> And the fetchapt derivation would:
> - Fetch Release and Release.gpg files from the repository
> - Verify digital signature
> - Fetch Packages file
> - Check hash value of Packages file against the hash value listed in
> Release file
> - Extract binary package path that correspond to the given package name
> from Packages file
> - Fetch the binary package
> - Check hash value of binary package against the hash value listed in
> Packages file

That doesn’t work, and it’s by design.
In order for nix (the package manager) to be able to install something,
it needs to know the input files *beforehand*, by hash. So nix **cannot**
evaluate a derivation where the source hash changes.

The one thing that could be done is completely automating the
version-bumping process, that is write a program that follows debian
releases, bumps the hashes, tests the functionality of the resulting
executables (!!) and then commits the new version to nixpkgs.

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