Local variables and mode hooks

[Lele Gaifax <lele@metapensiero.it>]

Hi all,

I'm trying to understand how can workaround a problem I'm facing when using
"local variables" I set in a `.dir-locals.el` file.

The problem is that the values are apparently assigned *after* the mode's hook
is run, so they are either "ignored" when I visit the source file, or
"considered" only when I actually modify it.

Let me try to explain.

In my Python sources, using Emacs python.el mode python-mode-hook, I usually
enable both `whitespace-mode` to highlight lines longer than `fill-column` (I
set `whitespace-line-column` to nil) and `flymake-python-pyflakes-load` to
check their syntax with pyflakes.

In a particular project I'm using Python 3, and I want to have a different
`fill-column` to make my coworkers happy, so I created a top level
`.dir-locals.el` file containing

  ((nil . ((fill-column . 75)))
   (python-mode . ((flymake-python-pyflakes-executable . "python3")
                   (flymake-python-pyflakes-extra-arguments . ("-m" "pyflakes")))))

When I visit/create a Python source, its local settings are changed
accordingly, but

a) whitespace highlights lines longer than the *global* value of
   `fill-column`, not its local setting

b) flymake shows syntax errors, because the "initial run" of pyflakes has been
   done with the standard settings, i.e. with its Python 2 variant

To make effect a) disappear I must execute M-: (whitespace-color-on), so it
"reinstall" its font-lock customization, while effect b) goes away as soon as
I change the buffer, triggering a new execution of pyflakes.

Is there some hook that I can use that runs *after* the major mode hooks *and*
the local variables settings got applied, so that I can force whitespace
refresh and trigger a flymake check?

Thanks in advance for any hint,
ciao, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.