GNU bug report logs - #75164
treesit-font-lock-fontify-region is easy to lost color on parse error. suggest to remain fontify on parse error.

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Eval Exec <execvy <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: treesit-font-lock-fontify-region is easy to lost color on parse
 error. suggest to remain fontify on parse error.
Date: Sun, 29 Dec 2024 00:25:24 +0800

Hello.
When I enable rust-ts-mode on a rust file, I found treesitter is easy
to make emacs buffer to lost color.
For example, on the following rust code:
```rust

struct Dog {
    name: String,
    age: u8,
}


struct ManyStruct {
    a: u8,
}

fn many_code(){
    fn fib(n: u32) -> u32 {
        if n == 0 {
            return 0;
        }
        if n == 1 {
            return 1;
        }
        fib(n - 1) + fib(n - 2)
    }
}

fn main() {
    // change below `//` to `/` to see the difference
    // {
}
```

the rust code is right, and the emacs buffer color is right on every
struct/functions.
But, if I change `// {` to `/ {`, then the rust code is wrong, this
buffer will lost all colors.
You can see the change on bellow images:

https://imgur.com/a/4Tnv0GJ

I suggest emacs can remain colors even if the code is wrong.

My emacs version info: GNU Emacs 31.0.50

Message #8 received at 75164 <at> debbugs.gnu.org (full text, mbox):

From: Charalampos Mitrodimas <charmitro <at> posteo.net>
To: Eval Exec <execvy <at> gmail.com>
Cc: 75164 <at> debbugs.gnu.org
Subject: Re: bug#75164: treesit-font-lock-fontify-region is easy to lost
 color on parse error. suggest to remain fontify on parse error.
Date: Mon, 30 Dec 2024 00:28:58 +0000

Hi,

Eval Exec <execvy <at> gmail.com> writes:

> Hello.
> When I enable rust-ts-mode on a rust file, I found treesitter is easy
> to make emacs buffer to lost color.
> For example, on the following rust code:
> ```rust
>
> struct Dog {
>     name: String,
>     age: u8,
> }
>
>
> struct ManyStruct {
>     a: u8,
> }
>
> fn many_code(){
>     fn fib(n: u32) -> u32 {
>         if n == 0 {
>             return 0;
>         }
>         if n == 1 {
>             return 1;
>         }
>         fib(n - 1) + fib(n - 2)
>     }
> }
>
> fn main() {
>     // change below `//` to `/` to see the difference
>     // {
> }
> ```
>
> the rust code is right, and the emacs buffer color is right on every
> struct/functions.
> But, if I change `// {` to `/ {`, then the rust code is wrong, this
> buffer will lost all colors.

Thanks for reporting this.

I attempted to reproduce this, using your example, when I change `// {`
to `/{` only "main" from `fn main()` loses color. The rest of the syntax
highlighting remains intact in my setup.


                            C. Mitrodimas

> You can see the change on bellow images:
>
> https://imgur.com/a/4Tnv0GJ
>
> I suggest emacs can remain colors even if the code is wrong.
>
> My emacs version info: GNU Emacs 31.0.50

Message #11 received at 75164 <at> debbugs.gnu.org (full text, mbox):

From: Yuan Fu <casouri <at> gmail.com>
To: Charalampos Mitrodimas <charmitro <at> posteo.net>
Cc: Eval Exec <execvy <at> gmail.com>, 75164 <at> debbugs.gnu.org
Subject: Re: bug#75164: treesit-font-lock-fontify-region is easy to lost color
 on parse error. suggest to remain fontify on parse error.
Date: Tue, 31 Dec 2024 13:02:52 -0800

> On Dec 29, 2024, at 4:28 PM, Charalampos Mitrodimas <charmitro <at> posteo.net> wrote:
> 
> Hi,
> 
> Eval Exec <execvy <at> gmail.com> writes:
> 
>> Hello.
>> When I enable rust-ts-mode on a rust file, I found treesitter is easy
>> to make emacs buffer to lost color.
>> For example, on the following rust code:
>> ```rust
>> 
>> struct Dog {
>>    name: String,
>>    age: u8,
>> }
>> 
>> 
>> struct ManyStruct {
>>    a: u8,
>> }
>> 
>> fn many_code(){
>>    fn fib(n: u32) -> u32 {
>>        if n == 0 {
>>            return 0;
>>        }
>>        if n == 1 {
>>            return 1;
>>        }
>>        fib(n - 1) + fib(n - 2)
>>    }
>> }
>> 
>> fn main() {
>>    // change below `//` to `/` to see the difference
>>    // {
>> }
>> ```
>> 
>> the rust code is right, and the emacs buffer color is right on every
>> struct/functions.
>> But, if I change `// {` to `/ {`, then the rust code is wrong, this
>> buffer will lost all colors.
> 
> Thanks for reporting this.
> 
> I attempted to reproduce this, using your example, when I change `// {`
> to `/{` only "main" from `fn main()` loses color. The rest of the syntax
> highlighting remains intact in my setup.

It’s indeed strange to see the whole buffer lost fontification. I don’t see it either.

Yuan

Message #14 received at 75164 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: Yuan Fu <casouri <at> gmail.com>
Cc: Charalampos Mitrodimas <charmitro <at> posteo.net>, Eval Exec <execvy <at> gmail.com>,
 75164 <at> debbugs.gnu.org
Subject: Re: bug#75164: treesit-font-lock-fontify-region is easy to lost color
 on parse error. suggest to remain fontify on parse error.
Date: Sun, 2 Mar 2025 04:20:55 +0000

Yuan Fu <casouri <at> gmail.com> writes:

>> On Dec 29, 2024, at 4:28 PM, Charalampos Mitrodimas <charmitro <at> posteo.net> wrote:
>>
>> Hi,
>>
>> Eval Exec <execvy <at> gmail.com> writes:
>>
>>> Hello.
>>> When I enable rust-ts-mode on a rust file, I found treesitter is easy
>>> to make emacs buffer to lost color.
>>> For example, on the following rust code:
>>> ```rust
>>>
>>> struct Dog {
>>>    name: String,
>>>    age: u8,
>>> }
>>>
>>>
>>> struct ManyStruct {
>>>    a: u8,
>>> }
>>>
>>> fn many_code(){
>>>    fn fib(n: u32) -> u32 {
>>>        if n == 0 {
>>>            return 0;
>>>        }
>>>        if n == 1 {
>>>            return 1;
>>>        }
>>>        fib(n - 1) + fib(n - 2)
>>>    }
>>> }
>>>
>>> fn main() {
>>>    // change below `//` to `/` to see the difference
>>>    // {
>>> }
>>> ```
>>>
>>> the rust code is right, and the emacs buffer color is right on every
>>> struct/functions.
>>> But, if I change `// {` to `/ {`, then the rust code is wrong, this
>>> buffer will lost all colors.
>>
>> Thanks for reporting this.
>>
>> I attempted to reproduce this, using your example, when I change `// {`
>> to `/{` only "main" from `fn main()` loses color. The rest of the syntax
>> highlighting remains intact in my setup.
>
> It’s indeed strange to see the whole buffer lost fontification. I don’t see it either.

Eval Exec, are there any steps missing in the recipe to reproduce this?

Can you reproduce it starting from emacs -Q?

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