Debounce textDocument/didChange events to avoid sending too many $/progress events

[jenanwise]

I'm using lsp-mode with Emacs. It sends a textDocument/didChange event with every keystroke, which causes rust-analyzer to respond with thousands of immediate $/progress events. In some clients, this can cause client performance issues (see e.g. #7590).

In my case, the issue is visual noise: lsp-mode displays each $/progress update in the modeline. These can be disabled by setting lsp-progress-function to 'ignore, but loses important information (particularly when loading a new project). See also brotzeit/rustic#251 which I believe has the same root issue.

The lsp-mode devs on discord suggested that rust-analyzer should be debouncing the textDocument/didChange events, and that a similar fix was made with clojure-lsp.

[lnicola]

I don't think we want debouncing just yet because it adds latency and makes for a worse user experience.

Instead, we should stop (doing the thing that's) sending those progress messages on each keypress, like in #9922. They don't even mean what they appear to mean.

[jenanwise]

Looks like 53d2050 solved it!