textDocument/formatting takes much longer than cargo fmt

[YaLTeR]

I'm using rust-analyzer cd24349 with autozimu/LanguageClient-neovim@12e65e7.

Running :call LanguageClient_textDocument_formatting() takes a really long while (upwards of 30 seconds on files from rav1e, like src/api/mod.rs), even though cargo fmt completes in half a second.

[matklad]

That seems pretty strage. For document formatting, we just shell out to rustfmt, so my best guess is that something weird is going on in the environment. I don't have a better advice than to just try to debug this issue.

[YaLTeR]

How do I go about debugging this?

[YaLTeR]

I noticed the same behavior in RLS: on some projects formatting via the request just takes a while for some reason. Maybe it's the language client that is to blame here.

[abbec]

I also get this when the lsp server has just been started and still has high CPU usage. After a while it settles though and becomes instant

[lnicola]

Maybe it's queued in the event loop?

[lnicola]

Let's close this as a dupe of #4054 (which is newer, but has more discussion and an arguably better title).