filterSource does not compose

[ElvishJerricco]

This is pretty frustrating, as it means we can't create nix expressions that reliably filter sources provided by users, e.g. callCabal2nix. With the current implementations, a user cannot use filterSource to filter out e.g. dist/ before passing it to callCabal2nix unless they want to sacrifice the cabal file filtering. In this case, they can use overrideCabal after the fact to reset the source to their own filtered version, but I think this just demonstrates why filterSource really ought to compose.

[shlevy]

Can't you do something like this in nixpkgs lib (obviously can be made easier to actually compose)?

composableFilterSource = f: s: { outPath = builtins.filterSource f s; inherit f; }

[shlevy]

Hell, you can even have composableFilterSource check s to see if it's the result of a previous call and compose automatically.

[ElvishJerricco]

@shlevy Yea I guess that works. Is it not desirable to fix this in builtins?

[shlevy]

Why write C++ when you could write nix? 😀

[ElvishJerricco]

Should we close this since we have cleanSourceWith in nixpkgs now?

[FRidh]

cleanSourceWith cannot be used with builtins.path to prevent the basename of the source to leak in.
Related issue regarding filterSource #885.

[stale]

I marked this as stale due to inactivity. → More info