Re: Add a separate mode for .dir-locals.el

[Eli Zaretskii <eliz@gnu.org>]

> From: João Távora <joaotavora@gmail.com>
> Date: Thu, 17 Oct 2019 22:35:33 +0100
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>, 
> 	Clément Pit-Claudel <cpitclaudel@gmail.com>, 
> 	emacs-devel@gnu.org
> 
>  Which class of problems is that?  I see only one problem that was
>  clearly identified and described: the .dir-locals.el file, and the
>  problem is that Flymake erroneously reports problems in that file.
> 
> The class can informally be described by "functionality not applicable and thus harmful to the manipulation of
> non-code lisp data files."

We already handle this in several places by explicitly exempting
.dir-locals.el from some operations that make no sense with it.  Why
ios this problem different?

>  What misdesign is that?
> 
> A failure to correctly model the differences between lisp code and
> lisp data.

There is no difference, not in general, not in Lisp.

>  I don't think I understand what you are saying here.  Can we step back
>  a notch and start by describing the problem in more detail?  What
>  diagnostics does Flymake produce in the case of .dir-locals.el, and
>  why does it produce that diagnostics?
> 
> I haven't checked, but if I had to guess, I would say it tries to invoke the byte-compiler on the file, which
> doesn't make any sense, as you know. As a result, bogus diagnostics are produced.

The byte compiler already knows to ignore .dir-locals.el, at least in
one of its commands.  If this is the only problem, maybe we need to
add that exemption in a couple of more places.

So I think we do need a detailed description of the problem, because
otherwise I think this discussion might be based on different
perceptions of what the problem is, and thus we have no common ground
for assessing the proposed solutions.

>  No, because this new mode is defined in a place that is not Flymake.
>  So when some change is done in Flymake that affects that mode, someone
>  needs to remember to update an unrelated mode in an unrelated source
>  file.
> 
> No. Simply no. We might be miscommunicating, but when a change happens in Flymake, the new mode
> proposed by Stefan need not be changed. At all.

I don't think I agree.  If Flymake is modified to do some meaningful
checks of .dir-locals.el, we may wish to remove this special major
mode as not needed anymore.

Anyway, I think this discussion needs to have a detailed description
of the problem, before we can continue talking about solutions.