custom option is broken for *new* packages

[srid]

Triggered (if not introduced) by #253 which made it so that buildFromSdist is applied (alphabetically) before the custom option, and for some reason x: x in Nix is not lazily propagating the argument.

       error: attribute 'hello_rust' missing

         at /nix/store/lz0159maimglzlpd6gmn0f02047mmih0-source/nix/modules/project/settings/all.nix:325:19:

          324|             (x: log.traceDebug "${name}.buildFromSdist ${x.outPath}" x)
          325|           ]) else x: x;
             |                   ^
          326|     };

       error: attribute 'hello_rust' missing

       at /nix/store/lz0159maimglzlpd6gmn0f02047mmih0-source/nix/modules/project/settings/default.nix:75:20:

           74|           in
           75|           lib.pipe super.${name} (
             |                    ^
           76|             # TODO: Do we care about the *order* of overrides?

Repro & Details

https://nixos.zulipchat.com/#narrow/stream/413949-haskell-flake/topic/.60custom.60.20setting.20stopped.20working

Proposed design change

Replace custom with two setting options:

• settings.<name>.init : drv: assigns the initial value before settings are applied
• settings.<name>.final : drv -> drv: transforms the final drv after the other settings are applied.

Open question: putting these two options in the same namespace as other settings is a bit of hack, because they are semantically different. Main questions: a) Is this the best we can do as proposal? b) if so, where should these options live?

(See Zulip for further proposals/ refinements/ ideas)

[shivaraj-bh]

It probably doesn’t make sense to add non-haskell pkg dependencies in custom, it should only be used for managing haskell packages, which it is meant for.

It made more sense to move hello_rust to otherOverlays and that did the job: shivaraj-bh/haskell-rust-ffi-template@bb60ff1

[shivaraj-bh]

it should only be used for managing haskell packages, which it is meant for.

If we stick to that, we needn’t worry about the order in which the setting is applied, do we?

[srid]

People use custom option to add Haskell dependency too. See https://community.flake.parts/haskell-flake/dependency#nixpkgs

Regarding, otherOvelays it won't compose like settings does. So if somebody defines otherOverlays in their own project, and imports your FFI template (which also defines otherOverlays), they will get conflict, because of this:

haskell-flake/nix/types/haskell-overlay-type.nix

Line 12 in 5dcb739

merge = lib.mergeOneOption;

(The reason for preventing merging of overlay lists here is due to nondeterministic semantics of list merge)

[shivaraj-bh]

It is breaking again after #286

Reproducer:

nix build github:shivaraj-bh/haskell-rust-ffi-template --override-input haskell-flake github:srid/haskell-flake/51bcbc27194e734a1524ac3d36e1539fba9a3baa

[srid]

@shivaraj-bh It is breaking, but it is not the same error.

From the issue description:

error: attribute 'hello_rust' missing

What I'm seeing when using master branch:

       error: attribute 'override' missing

       at /nix/store/fjvkr94j3lwca8y66zccn15rjwzqn0rd-source/pkgs/development/haskell-modules/lib/compose.nix:38:28:

           37|    */
           38|   overrideCabal = f: drv: (drv.override (args: args // {
             |                            ^
           39|     mkDerivation = drv: (args.mkDerivation drv).override f;

Could you open a separate bug report?

[srid]

Could you open a separate bug report?

Actually, wait. Let me figure out what the issue is first.

[srid]

#292