add strictUnusedTemplate to template type checker

[sod]

Which @angular/* package(s) are relevant/related to the feature request?

compiler

Description

referencing @angular/compiler 17.2.0

I like your addition of lint like features to your template compiler, listed on https://angular.dev/tools/cli/template-typecheck#troubleshooting-template-errors

Another warning it could throw. Unused templates:

<ng-template #foo>contents</ng-template>

If nobody accesses foo in the template or no @ViewChild('foo') annotation exists, this could be an error.

This could catch errors that happen because someone removed *ngTemplateOutlet but forgot to either remove or use the template otherwise.

[alxhub]

This is a little difficult to conceive, since it's hard to tell if the <ng-template> is used or not. It might be in the projected content of another component, where it could be queried by the name foo or simply TemplateRef. The compiler could theoretically know which content would be projected and thus subject to querying, but that's getting very nuanced. I think this is a good candidate for a lint error.

[sod]

I thought it was possible, as my intellij IDEA grays out unused templates:

But I admit it's not 100% accurate.

I didn't even know that child components could yoink templates from projected content. That of course complicates this inspection. Will see if I suggest this at angular-eslint instead.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}