nix: Base overridden packages on correct package versions

Previously we would use whatever version was in nixpkgs yet this may not be the version which the patch is supposed to be applied against.

Fixes #1 (closed).

changed the description

It's probably also a good idea to keep all-cabal-hashes.nix updated so that we don't end up trying to build a newer package that doesn't exist in all-cabal-hashes.

@vaibhavsagar indeed. The problem is I don't know of a convenient way to do this. Do you have any suggestions?

added 1 commit

• 1996de3e - nix: Base overridden packages on correct package versions

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@bgamari my preferred approach is to store the information in a .json file and use a bash script to update it, see here for example. This can be run as follows:

$ ./updater versions.json

to get an updated all-cabal-hashes.

added 2 commits

• a35f7b40 - nix: Base overridden packages on correct package versions
• 59852cd2 - Update cabal-hashes and add script to ease future updates

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added 1 commit

• de2bab6d - Update cabal-hashes and add script to ease future updates

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added 1 commit

• ef208584 - Update cabal-hashes and add script to ease future updates

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added 2 commits

• 07afc87c - nix: Fix infinite recursion
• 2de99c2c - Some changes from vaibhavsagar

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So this is a bit tricky as we don't have any easy way to ensure that the packages are called with the necessary native dependency derivations (e.g. zlib). We could override the version and src attributes, but this seems exceedingly hacky and the nix logic for fetching specific package sources from Hackage is not easily available.

For the record, here is the problem with the current approach in a nut-shell:

# test.nix
let
  nixpkgs = import <nixpkgs> {};
  haskellPackages = nixpkgs.haskellPackages.override (old: {
    overrides = self: super: {
      zlib = super.callHackage "zlib" "0.6.2" {};
    };
  });
in haskellPackages

You will find that nix build -f test.nix zlib fails with an infinite recursion since callHackage tries to pass haskellPackges.zlib to satisfy the zlib argument of the derivation produced by cabal2nix. However, the argument is supposed to be nixpkgs.zlib.

added 7 commits

• baeedd62 - Update cabal-hashes and add script to ease future updates
• e53f97d1 - nix: Fix infinite recursion
• 4b38c9cc - Some changes from vaibhavsagar
• b3bf1f8c - nix: Base overridden packages on correct package versions
• 418a98dc - Try something
• 01507bb1 - Another approach
• d63c861c - Revert buildHaskellPackages change

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This is no longer necessary with the new CI infrastructure.

closed