Expose local package derivations from .project

[mightybyte]

Currently, if I have to depend on a reflex-platform project alpha from another reflex-platform project beta, I've been using callCabal2nix. This is workable, but requires that I duplicate substantial amounts of alpha's nix expression in beta's default.nix file. This kind of situation would be improved if reflex-platform's project infrastructure exposed two things:

• The individual local package derivations generated by project so I don't have to use callCabal2nix when I depend on them.
• The full overridden package set that project generates so I can use that as my initial package set and avoid duplicating code specifying the transitive dependencies.

Is this doable?

[Ericson2314]

CC @ElvishJerricco

[3noch]

Seems like you could use passthru to pass just about anything through, though I think having a built-in API for this makes sense.

[ElvishJerricco]

I'm planning on moving project over to the NixOS module system at some point, which will make this trivial.

[ElvishJerricco]

For now the easiest thing to do is probably factor out the bits of alpha that need to be shared in dependent projects into a different file that alpha then imports in its default.nix. Then your other project can just import that.

[matthewbauer]

You should be able to get a package set from a reflex or obelisk project through the reflex attr like reflex.ghc:

nix build -f. reflex.ghc.hello

[ElvishJerricco]

@matthewbauer I think this is more about needing to duplicate a lot of your project's nix expressions. #225 will fix this by letting you define a module that can being merged into other projects easily.