Subject: Re: bug#67684: 30.0.50; Font lock rule conflict in js-ts-mode at level 4

From: Yuan Fu <[email-masked]>
Date: Sun, 10 Dec 2023 17:37:35 -0800

On 12/7/23 5:33 PM, Dmitry Gutov wrote:
> Hi!
>
> On 07/12/2023 12:07, Loïc Lemaître wrote:
>> I have noticed a font coloration issue in js-ts-mode when setting the 
>> treesit font lock level to 4: JSX attributes color is not the same 
>> than at level 3.
>> There should have a conflict between rules for "property_identifier" 
>> treesit type. The feature that triggers the conflict is "property" 
>> (of the level 4).
>>
>> You can reproduce the issue by following these steps:
>> - M-: (setq treesit-font-lock-level 4)
>> - M-x js-ts-mode on a JSX buffer
>>
>> Note that the bug already exists in Emacs 29.1.
>
> The attached patch seems to fix that.
>
> But it removes a function added by Yuan in e78e69b33189, while 
> reshuffling the highlights to reorder priorities.
>
> Yuan, do you remember why you did it that way back then? Perhaps I'm 
> missing some other conflict.
For a method invocation like obj.fn(), the "fn" should be fontified in 
function-call-face. However, "fn" is a property_identifier in the parse 
tree, so it would be fontified in property-use-face by the property 
feature. The predicate in the property feature makes sure we skip 
properties that are function invocations. And down the line in function 
feature, you'll see

(call_expression
       function: [(identifier) @font-lock-function-call-face
                  (member_expression
                   property:
                   (property_identifier) @font-lock-function-call-face)])

Here, the property_identifier is fontified in function-call-face.

Yuan