How to use overrideScope' with Emacs configured via programs.emacs

[terlar]

Reading through the documentation at:
https://nixos.org/nixpkgs/manual/#sec-emacs-config

I see that the recommended way to override packages is through the following method:

overrides = self: super: rec {
  haskell-mode = self.melpaPackages.haskell-mode;
  ...
};
((emacsPackagesNgGen emacs).overrideScope' overrides).emacsWithPackages (p: with p; [
  # here both these package will use haskell-mode of our own choice
  ghc-mod
  dante
])

However it seems to be no way to hook into that part via home-manager.

It is possible to set emacs and the last of packages through package and extraPackages. Perhaps introduce a configuration option called overrides?
If it is defined it would wrap the command with overrideScope'.

Is this understanding correct?

[rycee]

Yeah, you made a good point! The current design didn't allow such overrides. I added an programs.emacs.overrides option in the referenced PR. Can be used like so:

programs.emacs.overrides = self: super: {
  haskell-mode = self.melpaPackages.haskell-mode;
};