8000 Add Warning/Error if computed signals create a loop · Issue #61273 · angular/angular · GitHub
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marcelMaier opened this issue May 12, 2025 · 3 comments
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Add Warning/Error if computed signals create a loop #61273

marcelMaier opened this issue May 12, 2025 · 3 comments
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feature Issue that requests a new feature

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@marcelMaier
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Is your feature request related to a problem? Please describe.
No I can't find a related issue

🚀 feature request

Description

If I have for example a code like this:

 a = signal("A");
 b = signal("B");

 c = computed(() => {
  console.log("c");
  return this.a() + this.d();
 });

 d = computed(() => {
  console.log("d");
  return this.a() + this.c();
 });

// And a call like this in ngOnInit
  this.a.set("Ax");
  console.log(this.c());
  console.log(this.d());

Angular will show me the following in the developer console of the browser:

Image

I would expect angular to already show an error or warning right in VS Code etc.

Feature Type

I think it's related to both of them but I dont know for sure.

  • [ x ] Angular Language Service VSCode extension
  • [ x ] Angular Language Service server

Describe the solution you'd like

As described above the solution would be to already show an error before in the code editor so a bug like this can't be overseen also it would be useful if angular also wouldn't compile like that cause something has to be wrong if u have a loop inside of ur computed signals.

Describe alternatives you've considered

Have you considered any alternative solutions or workarounds?

Anything else relevant?
@marcelMaier marcelMaier added the feature Issue that requests a new feature label May 12, 2025
@atscott atscott transferred this issue from angular/vscode-ng-language-service May 12, 2025
@pkozlowski-opensource
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As described above the solution would be to already show an error before in the code editor so a bug like this can't be overseen also it would be useful if angular also wouldn't compile like that cause something has to be wrong if u have a loop inside of ur computed signals.

This is not feasible in general as signal dependency tracking is dynamic and a set of dependencies can change as the application runs - hence the runtime check / error.

@marcelMaier
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I know there will be cases where it's not possible to detect this but I think there are also cases like this where it is possible.

@alxhub
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alxhub commented May 12, 2025

As Pawel says, this is just not possible to determine statically in all but the simplest cases.

In your code snippet for example, the compiler cannot know that c or d aren't reassigned in a way that would avoid a cycle.

@alxhub alxhub closed this as not planned Won't fix, can't repro, duplicate, stale May 12, 2025
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@pkozlowski-opensource @alxhub @marcelMaier
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