Run latexmk with luatex or pdflatex depending on the local variable

Question

I want to run Latexmk automatically with the correct TeX-engine as set in the local file variable at the end of the file, for example:

%% Local Variables:
%% TeX-engine: luatex
%% End:

In my .emacs file I tried something like:

(add-hook 'LaTeX-mode-hook (lambda ()
  (push 
    '("Latexmk" "latexmk %(-PDF) %s" TeX-run-TeX nil t
      :help "Run Latexmk on file")
    TeX-command-list)

'("%(-PDF)"
  (lambda ()
    (if (equal TeX-engine 'luatex)
        "-lualatex" "-pdf"))))

but it doesn't work.

So how can I get the desired result?

Answer 1

I am going out on a limb and guessing that what you want is more along these lines (totally untested):

(eval-after-load "tex"
  '(progn
     (push '("Latexmk" "latexmk %(-PDF) %s" TeX-run-TeX nil t
             :help "Run Latexmk on file")
           TeX-command-list)
     (push '("%(-PDF)"
             (lambda ()
               (if (equal TeX-engine 'luatex)
                   "-lualatex" "-pdf")))
           TeX-expand-list)))

By using eval-after-load instead of a hook variable, I avoid having the same value pushed over and over again each time the mode is run. (You could achieve the same by using pushnew, since we are trying to push literally the same object on each run. Or by arraning for a hook function to remove itself after running.)