Very slow performance with 'Svelte for VS Code' extension on Sapper projects on networked drives

[Runi-c]

After trying the extension on a fresh project & seeing how fast it is, I'd like to reach out for some assistance in figuring out why the language server takes 6-7 seconds on every edit to HTML to begin serving language features again on Sapper projects on a networked drive.

Setting debug trace to "verbose" produces this series of messages when typing the below snippet and expecting IDE features:

slowsvelte.mp4

[Trace - 7:19:58 PM] Sending notification 'textDocument/didChange' ("<").
[Trace - 7:19:58 PM] Sending request 'textDocument/completion - (5)'.
[Trace - 7:19:58 PM] Sending request 'textDocument/signatureHelp - (6)'.
[Trace - 7:19:58 PM] Sending notification 'textDocument/didChange' ("B").
[Trace - 7:19:58 PM] Sending notification '$/cancelRequest' - (6).
[Trace - 7:19:58 PM] Sending request 'textDocument/signatureHelp - (7)'.
[Trace - 7:19:58 PM] Sending request 'textDocument/semanticTokens/full - (8)'.
[Trace - 7:19:58 PM] Sending notification 'textDocument/didChange' ("u").
[Trace - 7:19:58 PM] Sending notification 'textDocument/didChange' ("t").
[Trace - 7:19:58 PM] Sending notification '$/cancelRequest' - (7).
[Trace - 7:19:58 PM] Sending request 'textDocument/signatureHelp - (9)'.
[Trace - 7:19:58 PM] Sending notification 'textDocument/didChange' ("t").
[Trace - 7:19:58 PM] Sending notification 'textDocument/didChange' ("t").
[Trace - 7:19:58 PM] Sending notification '$/cancelRequest' - (9).
[Trace - 7:19:58 PM] Sending request 'textDocument/signatureHelp - (10)'.
[Trace - 7:19:58 PM] Sending notification 'textDocument/didChange' ("o").
[Trace - 7:19:59 PM] Sending notification '$/cancelRequest' - (10).
[Trace - 7:19:59 PM] Sending request 'textDocument/signatureHelp - (11)'.
[Trace - 7:19:59 PM] Sending request 'textDocument/documentColor - (12)'.
[Trace - 7:19:59 PM] Sending request 'textDocument/codeAction - (13)'.
[Trace - 7:20:02 PM] Sending notification '$/cancelRequest' - (5).
[Trace - 7:20:03 PM] Received response 'textDocument/completion - (5)' in 5839ms.
Using Svelte v3.32.3 from ~\Frontend\node_modules\svelte\compiler
Using Svelte v3.32.3 from ~\Frontend\node_modules\svelte\compiler
[Trace - 7:20:03 PM] Received notification 'textDocument/publishDiagnostics'.
[Trace - 7:20:03 PM] Received response 'textDocument/signatureHelp - (6)' in 5775ms.
[Trace - 7:20:04 PM] Sending request 'textDocument/codeAction - (14)'.
[Trace - 7:20:04 PM] Sending notification '$/cancelRequest' - (13).
[Trace - 7:20:09 PM] Received response 'textDocument/signatureHelp - (7)' in 11269ms.
Using Svelte v3.32.3 from ~\Frontend\node_modules\svelte\compiler
Using Svelte v3.32.3 from ~\Frontend\node_modules\svelte\compiler
[Trace - 7:20:09 PM] Received notification 'textDocument/publishDiagnostics'.
[Trace - 7:20:09 PM] Received response 'textDocument/semanticTokens/full - (8)' in 11304ms.
[Trace - 7:20:09 PM] Received response 'textDocument/signatureHelp - (9)' in 11076ms.
[Trace - 7:20:09 PM] Received response 'textDocument/signatureHelp - (10)' in 10879ms.
[Trace - 7:20:09 PM] Received response 'textDocument/signatureHelp - (11)' in 10716ms.
[Trace - 7:20:09 PM] Received response 'textDocument/documentColor - (12)' in 10669ms.
[Trace - 7:20:09 PM] Received response 'textDocument/codeAction - (13)' in 10594ms.
[Trace - 7:20:09 PM] Received response 'textDocument/codeAction - (14)' in 5515ms.

Trying the clean Svelte template and Sapper webpack template in different environments with trace on yields these results:

Local drive - Svelte template: 22ms
Network drive - Svelte template: 34ms
Local drive - Sapper Webpack: 307ms
Network Drive - Sapper Webpack: 6002ms

There didn't seem to be much difference with/without Typescript or with/without sveltestrap.

[dummdidumm]

Could you provide more info on how to reproduce this? Ideally the repo itself. If not, some steps on how to replicate it, like the contents of your package.json and svelte.config.js (if you have one), if you are using TS or not, if yes your tsconfig.json, how many files you project has, if it happens in all files or only some, etc etc.

[Runi-c]

The specific repo in question is private, but as detailed above, the stock Sapper Webpack template took 6002ms for IDE features to start working again. It's wholly bearable on a local drive, but on a networked drive it's unbearable.

After a bit more testing, it seems to be specifically the Sapper Webpack template, after the Typescript conversion script is ran, and npm install is ran. Before any of those things, the time taken is a tiny fraction of what I'm experiencing, and if the Typescript script isn't ran, the time is also extremely fast.

Therefore, here's the repro steps:

1. Open a command prompt in a networked location (not hosted locally).
2. npx degit "sveltejs/sapper-template#webpack" my-app
3. cd my-app
4. npm i
5. open the my-app folder in VSC with the Svelte for VS Code extension
6. open src/components/Nav.svelte, go to the bottom, and experiment with typing a <, <a, <d, etc. and see how long the extension takes to re-check the file and provide suggestions

[Runi-c]

Given the fact that the performance only deteriorates this excessively after the npm install, I went and tried removing the packages added by the typescript setup script one by one. The offending package seems to be svelte-preprocess. Why would the addition of this package cause the language server's performance to deteriorate by up to 20x specifically when editing HTML?

[dummdidumm]

Oh I have an idea, thanks for investigating. Could be due to sveltejs/svelte-preprocess#328 , I'll check when I have time.

[PuruVJ]

Has this been fixed? My IDE went from instataneous perf in the starter vite template to 4 seconds for intellisense to kick in after just 15 components 🥲

[dummdidumm]

Is your issue about networked, drives, too? If not, please open a separate issue with more details, ideally a reproduction repository.

[PuruVJ]

Ah ok

[PuruVJ]

Done @dummdidumm #1139 👍

[dummdidumm]

The latest version of svelte-preprocess does cache the resolved tsconfig files. Previously, they were loaded for each file, which might be slow on networked drives because IO operations could be slower. Could you try and report back if the situation improved?

[Runi-c]

Apologies for the long delay. There does seem to be a considerable improvement. It's still slow, but I understand there's only so much that can be done about that over a networked drive and for this reason I've switched to remote windows with VSCode which has vastly improved my development experience. Svelte language features are quite snappy over the remote window.

I think I can consider this solved though, the delay now seems to be about 2 seconds instead of 6-7+. Thanks for your efforts!

[rafaelspring]

@Roryl-c I am also seeing very slow plugin performance for large-ish svelte files (> 1000 LOC).

Setting debug trace to "verbose" produces this series of messages when typing the below snippet and expecting IDE features:

Can you let me know how to do this? I tried googling "vs code debug trace verbose" but no good results came up.

[Ayfri]

Any update? The issue is still occurring!