>>>> But can we do better?  I see that 'treesit-major-mode-setup'
>>>> adds the notifier
>>>> 
>>>>     (treesit-parser-add-notifier
>>>>      treesit-primary-parser #'treesit--font-lock-mark-ranges-to-fontify)
>>>> 
>>>> to 'after_change_functions'.  But why the treesit
>>>> 'after_change_functions' notifier is called after the
>>>> 'after-change-functions' hook?  Can we change their order?
>>> 
>>> Because we parse lazily. And I should’ve called them after-parse functions
>>> in the docstring (good thing I named them notifiers, not
>>> after-change-functions)—they get called after the parser re-parses, but the
>>> parser doesn’t have to re-parse immediately after a buffer change. It only
>>> re-parses when some Lisp asks for a node from the parse tree.
>>> 
>>> In practice, that usually happens in pre-redisplay-function where we set
>>> ranges for embedded parsers, which causes the primary parser to re-parse
>>> and return a root node for querying. As a (intended) side-effect, the
>>> notifiers get called and mark relevant regions to be re-fontified.
>> 
>> Would it be possible on the first attempt of Lisp code to access a node
>> to detect such a situation that there are some outdated nodes and
>> to update their ranges automatically?
>
> Probably not, since you need to have correct ranges to know
> which parser to use to get nodes in the first place.