Commit d1b6d2d0 authored by Guillaume Bouchard's avatar Guillaume Bouchard Committed by sternenseemann
Browse files

haskellPackages.callHackage: updating all-cabal-hashes do not invalidate callHackage 

Packages built with `haskellPackages.callHackage` won't be rebuilt when
updating `all-cabal-hashes`.

The removed comment was keeping a reference to the `cabal2nix` call,
which itself depends on `all-cabal-hashes`, in order to keep this file
during a garbage collection.

The tradeoff is between:

- The current behavior: a mass rebuild, any change of `all-cabal-hashes`
  triggers a rebuild of all the packages built with `callHackage` and
  packages which depend on them. This can take hours, and may happen
  after a "small" unrelated change (i.e. an user is bumping
  `all-cabal-hashes` in order to use a new package from hackage). It
  also have global impacts in a project (long rebuild in CI, new entries
  in cache, developers need to fetch the new entries, ...). In this
  context, `cabal2nix` entries are not garbage collected.
- The new behavior: No mass rebuild, but `cabal2nix` derivations need to
  be recomputed after a garbage collection. This is usually fast (a few
  seconds by call), linear with the number of calls and should not
  happen a lot (i.e. users are not garbage collecting everyday).

See https://github.com/NixOS/nixpkgs/issues/194751 for details.
parent 81df6d7f

nixos/doc/manual/from_md/release-notes/rl-2211.section.xml

+16 −0
Original line number Diff line number Diff line
@@ -1694,6 +1694,22 @@ services.github-runner.serviceOverrides.SupplementaryGroups = [ 
          <literal>picom</literal> to quit instead.

        </para>

      </listitem>

      <listitem>

        <para>

          <literal>haskellPackage.callHackage</literal> is not always

          invalidated if <literal>all-cabal-hashes</literal> changes,

          leading to less rebuilds of haskell dependencies.

        </para>

      </listitem>

      <listitem>

        <para>

          <literal>haskellPackages.callHackage</literal> and

          <literal>haskellPackages.callCabal2nix</literal> (and related

          functions) no longer keep a reference to the

          <literal>cabal2nix</literal> call used to generate them. As a

          result, they will be garbage collected more often.

        </para>

      </listitem>

    </itemizedlist>

  </section>

</section>

nixos/doc/manual/release-notes/rl-2211.section.md

+4 −0
Original line number Diff line number Diff line
@@ -529,4 +529,8 @@ Available as [services.patroni](options.html#opt-services.patroni.enable). 


- The option `services.picom.experimentalBackends` was removed since it is now the default and the option will cause `picom` to quit instead.



- `haskellPackage.callHackage` is not always invalidated if `all-cabal-hashes` changes, leading to less rebuilds of haskell dependencies.



- `haskellPackages.callHackage` and `haskellPackages.callCabal2nix` (and related functions) no longer keep a reference to the `cabal2nix` call used to generate them. As a result, they will be garbage collected more often.



<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->

pkgs/development/haskell-modules/make-package-set.nix

+5 −9
Original line number Diff line number Diff line
@@ -161,17 +161,13 @@ let 
    src    = "${component}/${name}.cabal";

  };



  # Adds a nix file as an input to the haskell derivation it

  # produces. This is useful for callHackage / callCabal2nix to

  # prevent the generated default.nix from being garbage collected

  # (requiring it to be frequently rebuilt), which can be an

  # annoyance.

  # Adds a nix file derived from cabal2nix in the passthru of the derivation it

  # produces. This is useful to debug callHackage / callCabal2nix by looking at

  # the content of the nix file pointed by `cabal2nixDeriver`.

  # However, it does not keep a reference to that file, which may be garbage

  # collected, which may be an annoyance.

  callPackageKeepDeriver = src: args:

    overrideCabal (orig: {

      preConfigure = ''

        # Generated from ${src}

        ${orig.preConfigure or ""}

      '';

      passthru = orig.passthru or {} // {

        # When using callCabal2nix or callHackage, it is often useful

        # to debug a failure by inspecting the Nix expression