Re: Average-user-facing interface for tree-sitter

[Theodor Thornhill <theo@thornhill.no>]

Yuan Fu <casouri@gmail.com> writes:
>> 
>> It seems we've had some regressions _after_
>> 851a8f65e9a6b00b51f6a41f4c8f2ec2a797862b, I presume with the major mode
>> toggles, so font-locking has ceased to work properly.  One thing I see
>> is that the "warn" isn't a symbol in the new toggle mechanism, so it
>> errors out.  But even after that has been fixed it still doesn't work.
>> 
>> Why would we want to init the whole js-mode if we already know that we
>> don't want to use it?
>
> Yes, sorry, I made some further changes to js-mode. Could you have a look and see if it makes sense?
>
> Thanks,
> Yuan

I'm not sure I really like the new changes.  Now we init everything in
js-mode in addition to everything treesitter related.  So now stuff like

```
  (setq-local font-lock-defaults
              (list js--font-lock-keywords nil nil nil nil
                    '(font-lock-syntactic-face-function
                      . js-font-lock-syntactic-face-function)))
  (setq-local syntax-propertize-function #'js-syntax-propertize)
  (add-hook 'syntax-propertize-extend-region-functions
            #'syntax-propertize-multiline 'append 'local)
  (add-hook 'syntax-propertize-extend-region-functions
            #'js--syntax-propertize-extend-region 'append 'local)
  (setq-local prettify-symbols-alist js--prettify-symbols-alist)

  (setq-local parse-sexp-ignore-comments t)

```
And many before/after change functions are enabled.  I don't see any
reason why they should be, and in many cases this will _absolutely_
be difficult to reason about.  That's why I did the 'avoid cc-mode
altogether' approach earlier.  I'm interested to know why this is
perceived as better than the 'js-use-treesitter' thing we had earlier.
Why not just check for 'global-treesit-mode' or something and then just
jump over everything else than treesit inits?


Also see suggested diff to get ts-mode to work again, as it couldn't
activate in the current revision.  This means that the only reason that
js-mode works is because we set the font-lock-defaults earlier.
Wouldn't that mean it works only by accident?


diff --git a/lisp/progmodes/ts-mode.el b/lisp/progmodes/ts-mode.el
index c23f2bec05..670e103eec 100644
--- a/lisp/progmodes/ts-mode.el
+++ b/lisp/progmodes/ts-mode.el
@@ -276,6 +276,8 @@ ts-mode
                       "function_declaration"
                       "lexical_declaration")))
   ;; Font-lock.
+  (unless font-lock-defaults
+    (setq font-lock-defaults '(nil t)))
   (setq-local treesit-font-lock-settings ts-mode--font-lock-settings)
   (setq-local treesit-font-lock-feature-list '((minimal) (moderate) (full)))
 


Thanks,
Theo