Subject: bug#73414: eglot: using auto-revert-mode and git checkout corrupts diagnostics

From: Romain Ouabdelkader <[email-masked]>
Date: Sat, 21 Sep 2024 21:13:35 +0200

Hello,

With auto-revert-mode and eglot enabled, using a git checkout to change
branch will leave invalid buffer diagnostics.

Emacs version: GNU Emacs 30.0.91
Operating system: Mac OS X
Eglot version: reproduced with emacs -Q on emacs30 pretest.
Server used: pyright

Steps to reproduce:

Using the following file:

```
def print_lorem_ipsum():
    print("Lorem ipsum dolor sit amet, consectetur adipiscing elit.")

def print_lorem_ipsum_upper():
    print("LOREM IPSUM DOLOR SIT AMET, CONSECTETUR ADIPISCING ELIT.")
```

1. Initialize the git repository:

$ git init
$ git add a.py
$ git commit

$ git checkout -b test
# edit a.py and remove the function print_lorem_ipsum_upper
$ git add a.py
$ git commit

2. Start emacs on the test branch:

$ emacs -Q a.py
M-x auto-revert-mode
M-x eglot

3. Then go to the main branch:

$ git checkout main

After auto-revert-mode triggers a file reload, eglot will report that the
function print_lorem_ipsum_upper is duplicated. (See screenshot in
attachment)
See also the `eglot-events-buffer` logs in attachment.

In this state, even if you delete the function and rewrite it, the error
will stay.
The only way to fix the issue is to do a eglot-reconnect.

I can reproduce the issue on emacs30 with built-in eglot and I didn't have
the problem on emacs29 with eglot 1.15 from ELPA.

Thanks.