Better error message for misplaced NgSwitchDefault

[jrsun]

🐞 bug report

Affected Package

The issue is caused by package @angular/common.

Is this a regression?

No.

Description

This is a request for clearer error messaging. When an NgSwitchDefault directive erroneously exists outside of a NgSwitch, the error message appears to be import-related, rather than a syntax error: No provider for NgSwitch found in NodeInjector...

🔬 Minimal Reproduction

1. https://proxy-ga.blitzz.co/proxy/123456/stackblitz.com/edit/angular-ivy-zexnwp?file=src/app/app.component.ts
2. See console for error.

🔥 Exception or Error

ERROR Error: NG0201: No provider for NgSwitch found in NodeInjector

🌍 Your Environment

Angular Version:

any

Anything else relevant?

[stefanoww]

I can take it. Some proposal for descriptive error message?

[jelbourn]

It would be something like "NgSwitchDefault must be inside NgSwitch". The error should also only be reported in dev mode

[petebacondarwin]

I imagine that this will have to be achieved by making the injection optional and then checking the argument for null in the constructor? This will add a small amount to the size of applications built with common. Any better ideas?

[AndrewKushnir]

This will add a small amount to the size of applications built with common. Any better ideas?

We can also wrap it in if (ngDevMode) { ... } (example) to tree-shake away extra code (the check itself + the error message) in prod bundles.

[AndrewKushnir]

Btw, I think it'd be worth adding the same check into the NgSwitchCase directive as well (in addition to the NgSwitchDefault one).

[stefanoww]

I am really egear to help with that, but for sure I will need your help. Current error as I well figuret out is quite generic and is throw by the throwProviderNotFoundError method. Does your proposal is to make the NgSwitch optional in NgSwitchDefault and check in the constructor wheter it's exist and if not throw an custom error in dev mode?

[petebacondarwin]

I am really egear to help with that, but for sure I will need your help. Current error as I well figuret out is quite generic and is throw by the throwProviderNotFoundError method. Does your proposal is to make the NgSwitch optional in NgSwitchDefault and check in the constructor wheter it's exist and if not throw an custom error in dev mode?

Yes - that was my suggestion. I don't know if there would be any better way...?