bug#68246: 30.0.50; Add non-TS mode as extra parent of TS modes

[Yuan Fu <casouri@gmail.com>]

> On Jan 15, 2024, at 6:32 PM, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> 
>>> Please don't call it "language".  That'd be confusing.  LSP is about
>>> programming languages, so "language" is natural there.  But in Emacs,
>>> a major mode is more general than that.  For example, it is not
>>> unthinkable to consider mail-mode to be the extra-parent of
>>> message-mode (or vice versa) -- but what is the "language" in that
>>> case?
>> Isn't the language for such modes in this paradigm just the empty set?
> 
> I'm not too worried about those cases, indeed.
> I'm more worried about the taxonomy of languages.
> We currently have the taxonomy of major modes, with which we're pretty
> familiar, and we've had many years to learn about its downsides,
> complexity, as well as how to deal with them, but for languages we're
> only familiar with the easy cases, which makes us judge the idea in
> a way that may prove naive.

I don’t have anything insightful to contribute, but want to point out that in Emacs, “language” doesn’t always mean programming language. “Language” can also mean Chinese, English, etc, and Emacs are quite often used for editing natural language text. So it warrants some caution when using “language” to mean programming language specifically.

> 
> IME, deciding what is the type of the content of a buffer is usually
> trivial but with some notable caveats, such as XPM or Postscript files,
> or "container formats" (like `.deb` or `.odt`, as well as things like
> DocBook which can be considered either as their own format or as XML),
> or "sublanguages" such as C being a subset of C++, or Javascript being
> a subset of Typescript.  And I suspect the info we need will not always
> be quite the same.
> 
> So while there might be a good case to be made to add some API functions
> to query the language/type(s) of a given buffer (I'm not sure we'd need
> the language of a given major mode, OTOH), or to find the preferred
> mode(s) for a given language/type, I think it's worthwhile to try and
> tweak our major mode taxonomy because it is information we must have
> and information we know we will always have, so we should strive to make
> it as good as we can.
> 
> It shouldn't make it any harder to add language/type API functionality.
> On the contrary it should make it easier.
> 
> [ As suggested elsewhere in this thread, we could even try and merge
>  those taxonomies, e.g. using extra parents of the form `LANG-lang`.  ]
> 
> As I said at the very beginning of this long thread, I'm not completely
> sure how well my proposal will play out: the upsides are in plain sight,
> but it may bump into real problems.  [ I'm actually surprised by Eli's
> optimism about it 🙂 ]
> But we won't know until we try it.
> 
> 
>        Stefan
>