Removing ViewRef causes error in Ivy

🐞 bug report

Affected Package

The issue is caused by package @angular/core

Is this a regression?

Yes, the previous version in which this bug was not present was: 8

Description

I have a dropdown directive that creates a new view in a ViewContainerRef of dropdowns host component. If that new view also has this directive it can create another view. In ngOnDestroy of that directive I remove this view from ViewContainerRef.

When parent dropdown is removed, I get an error in Ivy on destruction of nested directive created view.

Seems like destruction of first view causes destruction of the second view in sync and when I attempt to remove second view I get error, because length is already updated as if parent view is removed (length is 1): https://github.com/angular/angular/blob/0879d2e85d29c33c10e7314e49f5e4f0cc6ce2ba/packages/core/src/render3/view_engine_compatibility.ts#L209-L211

However both views are still there in indexOf: https://github.com/angular/angular/blob/0879d2e85d29c33c10e7314e49f5e4f0cc6ce2ba/packages/core/src/render3/view_engine_compatibility.ts#L299-L302

So nested view reports being at index of 1 and this assertion fails thinking there is only index of 0 because it thinks length is 1: https://github.com/angular/angular/blob/0879d2e85d29c33c10e7314e49f5e4f0cc6ce2ba/packages/core/src/render3/view_engine_compatibility.ts#L321-L331

🔬 Minimal Reproduction

Toggle parent, then toggle child, then toggle parent again to have them both removed https://stackblitz.com/edit/angular-ivy-viewref-bug

Here’s working example on Angular 8 with ViewEngine: https://stackblitz.com/edit/angular-ve-viewref

🔥 Exception or Error

ERROR
Error: ASSERTION ERROR: index [Expected=> 1 < 1 <=Actual]

🌍 Your Environment

Angular Version:

10.0.5

[waterplea]

I think removing function should be fine. I’ll look into it more later, @pkozlowski-opensource I will try to make a PR.

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