pkgs.haskell.lib.packageSourceOverrides

The following is the current implementation of this function.

packageSourceOverrides =
    overrides: self: super:
    pkgs.lib.mapAttrs (
      name: src:
      let
        isPath = x: builtins.substring 0 1 (toString x) == "/";
        generateExprs = if isPath src then self.callCabal2nix else self.callHackage;
      in
      generateExprs name src { }
    ) overrides;