file-notify-add-watch watch a directory doesn't work when backup file disabled or edit file in vscode?

[jadestrong]

Thank you for the bug report

• I am using the latest version of lsp-mode related packages.
• I checked FAQ and Troubleshooting sections
• You may also try reproduce the issue using clean environment using the following command: M-x lsp-start-plain

Bug description

I use doom-emacs and rust-analyzer, when edit the Cargo.toml file in doom-emacs or vscode it will not trigger the workspace/didChangeWatchedFiles event.

lsp-mode use file-notify-add-watch to watch a directory change to trigger workspace/didChangeWatchedFiles.

It works in vanilla Emacs because it enabled backup file feature, when edit and save a file will trigger a create or rename or delete event .
When disable this feature such as doom-emacs or edit the file in vscode, it only change the file content, only trigger a file change event, so directory change event will not work as expect.

Steps to reproduce

doomemacs/doomemacs#5630
brotzeit/rustic#322

When edit and save Cargo.toml file in doom-emacs and vscode, only file change event:

When edit in vanilla Emacs:

Expected behavior

When edit Cargo.toml in vscode or emacs without backup file, can also reload rust-analyzer

Which Language Server did you use?

rust-analyzer

OS

MacOS

Error callstack

No response

Anything else?

No response

[laampui]

similar issue: #facebook/create-react-app#9056

same here...

[danp]

Running into this myself, on macOS. Maybe related to me using backup-by-copying t that I learned from #3516 / #4112? Not sure.

It does seem less than ideal that file-notify-add-watch can't detect changes to existing files, at least the way it's ending up working on macOS. There was some talk about improving in this bug but it was closed.

Is there something else lsp-mode could do? Would having (optional) support for using an external process for watching directories/files for changes help at all? At least then there would be a way to plug something in that can detect all creates/changes/deletes, I think.