Performance Issues: Slow Response, Requires Frequent Restarts, Affects TS Files

[bmitchenko]

Is this a regression?

Unknown, but recent updates seem to have worsened the issue.

Description

The Angular Language Service in VSCode is significantly slowing down development. The extension often becomes unresponsive, leading to delays in template and TypeScript file analysis. Restarting the extension temporarily resolves the issue but hampers workflow. These problems are consistent with the experiences shared by users in the VSCode Marketplace reviews.

Key Issues:

• Extremely slow response time when editing Angular templates or TypeScript files.
• The extension requires frequent restarts to restore functionality.
• Development performance is degraded even when working on non-template (TS) files.

Bug Type

What does this bug affect

• Angular Language Service VSCode extension
• Angular Language Service server

Reproduction

Steps to reproduce the behavior:

1. Open an Angular workspace in VSCode with the Angular Language Service enabled.
2. Begin editing a template or TypeScript file.
3. Observe the increasing latency in language features (e.g., intellisense, error highlighting).
4. Notice that restarting the extension temporarily improves performance, but the issue recurs.

Expected behavior

The Angular Language Service should provide quick and responsive language features without requiring frequent restarts or causing performance issues.

🌍 Your Environment

Angular Version:

Angular: 19.0.1
Angular CLI: 19.0.2
Node: 22.9.0
Package Manager: npm 10.8.3
OS: win32 x64

Extension Version:

19.0.3

VSCode Version:

Version: 1.96.1 (user setup)
Commit: 42b266171e51a016313f47d0c48aca9295b9cbb2
Date: 2024-12-17T17:50:05.206Z
Electron: 32.2.6
ElectronBuildId: 10629634
Chromium: 128.0.6613.186
Node.js: 20.18.1
V8: 12.8.374.38-electron.0
OS: Windows_NT x64 10.0.26100

Operating System:

Windows 11 Home 24H2 OS Build 26100.2314

Extension options:

Default settings.

[glued]

seeing this too ever since updating to Angular 19

[jpike88]

I wish the angular team would treat performance with higher consideration. I'm sick of vscode locking up and crashing after a bunch of work is done, it's a horrible way to work.

[ShacharHarshuv]

I'm not sure if it's the same issue, but I want to contribute my experience -

• As far as I can see it only affects "find references" / "go to definition" and similar. Intellisense seems to be working fine, but I might be missing cases where it's not.
• Disabling the Angular Language Service makes typescript functionality work fine (no excessive delays) but obviously it's not a solution because I won't get language support for html.
• It's reproducing in every extension version I checked, with my project being in Angular 19.
• I checked out an older version of my project that used Angular 18, the issue is still reproducing, even if I install the matching version of the extension.
• I don't notice restarting helping at all. (which makes we wonder if it's the same issue)

This is right now the only reason I don't use vscode (opting for WebStorm, which works fine). Would love some updates if this is something that is going to be fixed so I can try vscode again.

[Canolz]

cmd/ctrl clicking on an import and getting a result takes 5-15 seconds. Depending if it's in the node modules it takes even longer. After turning it off and doing the same it gives me instantaneous results no matter where it is located. I am on a M2 Macbook pro max 64 GB (Sequoia 15.3.2)

[atscott]

In the past for performance debugging, we have often used https://github.com/atscott/ng-speed-rebuild. I haven't observed performance issues that have previously come up when something is awry.

To those experiencing issues:

• Are you still seeing them
• Can you provide a reproduction repository
• Is it reproducible in https://github.com/atscott/ng-speed-rebuild
• Are you also seeing slow builds for the application? This could be a duplicate of AOT builds with TypeScript 5.6 or later are slower in Angular 19 angular#59040 in that case.

[jpike88]

Update: I moved to zed and am using the angular LSP on that. My performance issues have all disappeared!

(Note: they're about to release their debugger so I haven't tested with that open yet.)

[atscott]

Update: I moved to zed and am using the angular LSP on that. My performance issues have all disappeared!

Thats a really interesting datapoint. Since the extension uses the language server npm package that we publish here, there’s not much difference in how these should perform other than VSCode vs Zed as an IDE. There’s very little we do on the client side for the VSCode extension other than short-circuit prevention from even sending requests to the server when not in an Angular context.

[bmitchenko]

I'd like to point out that the issue is not with the build process, but with intellisense in VS Code. After disabling the Angular Language Service plugin, intellisense starts working instantly. With the plugin enabled, there are significant delays in autocompletion and other intellisense features.

This problem specifically occurs in large repositories, while performance is normal in smaller ones. This makes it difficult to create a simple reproduction case.

[atscott]

I'd like to point out that the issue is not with the build process, but with intellisense in VS Code

This is one and the same. The language service needs to compile the whole program in order to provide autocomplete features. NgModules require global knowledge. Standalone components can make this better and there is work necessary to improve partial compilation in this area.

Autocomplete is disabled in TypeScript contexts. It should not be affecting anything other than autocomplete inside templates. Incremental compilation for changes to template files should be reasonably fast.

[ShacharHarshuv]

I tried again now with both my repo and the example repo and it seems to work much better. There is a noticeable delay in the first "Go to action" but I've tried a bunch after it and the rest are smooth, which mean I can work.
I'm not sure what got updated though that fixed it (vscode / LS / windows..?)
I'll update if I see that happening again!

[atscott]

Given that many folks have reported not being able to reproduce this anymore, I'm going to close this rather than keeping it as a catch-all for any performance issues that might happen in the future, which may have different causes. If problems come up again, please feel free to open a new issue.