bug#51926: 29.0.50; Narrow to defun fails with Javascript async functions

bug#51926: 29.0.50; Narrow to defun fails with Javascript async functions

[Matthias Meulien]

1. Create a buffer and enable `js-mode' in that buffer
2. Enter the following function definition:

async function test_async() {
  return true;
}

3. Move cursor past the "f" of the "function" keyword.

4. Call `narrow-to-defun' (C-x n d) and observe that the buffer now
displays the following:

function test_async() {
    // nothing to do
}

This is wrong (async has disappeared).



In GNU Emacs 29.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo version 1.16.0)
 of 2021-11-14 built on carbon
Repository revision: 2ff42ad0e8468a5979a8c5db90333d9c2949bd2e
Repository branch: dev/mm
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)

Configured using:
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Configured features:
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bug#51926: 29.0.50; Narrow to defun fails with Javascript async functions

[Lars Ingebrigtsen]

Matthias Meulien <orontee@gmail.com> writes:

> 4. Call `narrow-to-defun' (C-x n d) and observe that the buffer now
> displays the following:
>
> function test_async() {
>     // nothing to do
> }
>
> This is wrong (async has disappeared).

Yup; I can reproduce this in Emacs 29, too.  I've poked at it now, and
it's surprisingly difficult to fix this, due to the way these functions
are constructed.  But I think I've got it working now in Emacs 29.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#51926: 29.0.50; Narrow to defun fails with Javascript async functions

[Matthias Meulien]

[-- Attachment #1: Type: text/plain, Size: 488 bytes --]

> Yup; I can reproduce this in Emacs 29, too.  I've poked at it now, and
> it's surprisingly difficult to fix this, due to the way these functions
> are constructed.


I must confess I tried to fix it before I create the bug report (as I
usually do since I feel like maintainers are already quite busy...) but
gave up: There are so many regexps to match the function keyword, the
cache, etc.


But I think I've got it working now in Emacs 29.


Thanks a lot! I'll test this this evening.

[-- Attachment #2: Type: text/html, Size: 1005 bytes --]

bug#51926: 29.0.50; Narrow to defun fails with Javascript async functions

[Matthias Meulien]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Yup; I can reproduce this in Emacs 29, too.  I've poked at it now, and
> it's surprisingly difficult to fix this, due to the way these functions
> are constructed.  But I think I've got it working now in Emacs 29.

I pulled last HEAD of master which includes:

   6cad3dc75e..: Lars Ingebrigtsen 2021-11-18 Fix `narrow-to-defun' in
   "async function" in js-mode

Unfortunately it has improved but it doesn't always work as
expected. With a buffer with following content:

async function test() {
    // cursor here
}

it now works when cursor is on the first line ("async function test...")
AND not after the opening brace. After that brace, on first line or
second line, it fails...
-- 
Matthias

bug#51926: 29.0.50; Narrow to defun fails with Javascript async functions

[Lars Ingebrigtsen]

Matthias Meulien <orontee@gmail.com> writes:

> Unfortunately it has improved but it doesn't always work as
> expected. With a buffer with following content:
>
> async function test() {
>     // cursor here
> }
>
> it now works when cursor is on the first line ("async function test...")
> AND not after the opening brace. After that brace, on first line or
> second line, it fails...

Hm, I thought I had tested that case...  Oh!  When fixing a compilation
warning, I messed up that code path.  This should work better now.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no