I have a working emacs setup in nix using home-manager emacs. init.el etc are not in the nix setup but usually; emacs config. It loads packages and includes code from extraConfig option in default.el. The extra config includes code like

(setq    envrc-direnv-executable "${pkgs.direnv}/bin/direnv")

Unfortunately this loads after my init.el

Has anyone got an example of getting code like that (using nix paths) to be loaded before or as part of init.el

Is there an issue with byte compilation and "internal" functions in a package? I started noticing a failure to call private functions.
relatively minimal example:

{ pkgs, ... }:
pkgs.emacsWithPackagesFromPackageRequires {
  packageElisp = ''
  (require anki-editor)
  '';
  extraEmacsPackages = epkgs: [
    epkgs.anki-editor
  ];
}

Error:

❯ nix build .#emacs-anki-editor && ./result/bin/emacs -Q --batch --eval "(progn (require 'anki-editor) (message \"%s\" (apropos-internal \"anki-editor--anki-connect-invoke\")) (anki-editor--anki-connect-invoke))"
(anki-editor--anki-connect-invoke)

Error: void-function (anki-editor--anki-connect-invoke)
  mapbacktrace(#f(compiled-function (evald func args flags) #<bytecode 0x63863d603aef0e5>))
  debug-early-backtrace()
  debug-early(error (void-function anki-editor--anki-connect-invoke))
  (anki-editor--anki-connect-invoke)
  (progn (require 'anki-editor) (message "%s" (apropos-internal "anki-editor--anki-connect-invoke")) (anki-editor--anki-connect-invoke))
  command-line-1(("--eval" "(progn (require 'anki-editor) (message \"%s\" (apropos-internal \"anki-editor--anki-connect-invoke\")) (anki-editor--anki-connect-invoke))"))
  command-line()
  normal-top-level()
Symbol’s function definition is void: anki-editor--anki-connect-invoke