bug#64275: 30.0.50; [PATCH] Improve sigil font-lock match for elixir-ts-mode

[Wilhelm Kirschbaum]

Dmitry Gutov <dmitry@gutov.dev> writes:

> On 25/06/2023 12:00, Wilhelm Kirschbaum wrote:
> >         "~" @font-lock-string-face
> >         (sigil_name) @elixir-ts-font-sigil-name-face
> >         (:match "^[rR]$" @elixir-ts-font-sigil-name-face))
> >        @font-lock-regexp-face
> > -     (sigil
> > -      "~" @font-lock-string-face
> > -      (sigil_name) @elixir-ts-font-sigil-name-face
> > -      quoted_start: _ @font-lock-string-face
> > -      quoted_end: _ @font-lock-string-face
> > -      (:match "^[HF]$" @elixir-ts-font-sigil-name-face)))
> > -
> > +     (sigil) @font-lock-string-face)
>
> Hi Wilhelm!
>
> Should we continue to use elixir-ts-font-sigil-name-face, 
> though?

Hi :)

We still need to match only the sigil_name part, so can't use the
@font-lock-string-face as it will exclude the '~', therefore we 
need a
custom font for the match.  This is only true for ~r/regex content 
here/ and
~R/regex content here/, or variance ~r(regex content here) 
etc. where
the font for the regex part is different than the font for the 
sigil
prefix.

Perhaps there is another way to both apply a font with
@font-lock-string-face and exclude it from the :match, but last 
time I
checked this was not possible.

> With the new patch, it will continue highlight the sigil name 
> ("r") in
> regexps, but no in other sigil types (s/c/w).

Incorrect, just below there is a:

          (sigil) @font-lock-string-face)

without a match, so they will be highlighted, but just more 
generically
as we don't know which sigils the user might have assigned.

> What's your opinion on that?

As a baseline it makes sense to me to apply font-lock-string-face 
to all
sigils, as they can be user defined.  Some are language core 
sigils,
like the ~r and ~R sigils and then there are common library 
accepted
sigils like ~H and ~F which can effectively be seen as part of the
language, these can be added over time as we improve this mode. 
The
initial ideas was to try and match a complete list, but won't 
work.
Users can also define sigils in their projects, so its better to 
rely on
the grammar to tell us its a sigil.

I ran the current patch for over a month and feels correct.

Wilhelm