Plural expression within ng-container with ngIf prevents following markup from being rendered

[anton-github]

🐞 bug report

Affected Package

It seems like any angular version with Ivy enabled is affected.

Is this a regression?

Since Ivy is enabled by default in the newer versions I would say yes, it's a regression.

Description

Plurals ICU expressions prevent following markup from being rendered when used within ng-container with ngIf on it. For version 10 it's true only for subsequent renderings, see examples in the next section.
Short code example:

  <ng-container *ngIf="true">
    you have {{ 1 }} {1, plural, one {task} other {tasks}} to do
  </ng-container>

On subsequent renderings the code above will render you have 1 task

🔬 Minimal Reproduction

Toggle block visibility by clicking button to see how the result is changed

https://stackblitz.com/edit/plural-ng8 - all is OK
https://stackblitz.com/edit/plural-ng9rc1 - is OK with Ivy disabled, otherwise the behavior is wrong for both first and subsequent renderings
https://stackblitz.com/edit/plural-ng10 - is OK with Ivy disabled, otherwise the behavior is wrong only for subsequent renderings

🔥 Exception or Error

Nothing is logged

🌍 Your Environment

Angular Version:
Please see stackblitz examples dependencies above

[petebacondarwin]

It appears that in the ɵɵtext() instruction for the " to do " string, the call to appendChild() fails because it is not able to find a renderParent - (getRenderParent() returns null).

[petebacondarwin]

Actually that is a redherring, since at the point the appendChild() is called, this node is not yet attached to the node tree, since it is part of an ngIf, which has not yet been applied.

On further digging, I see that on the first rendering, the tNode.next for the ICU does have a reference to the text node, but on the second rendering this property is null. So we need to work out why the ICU tNode is losing the link to the following text tNode on second rendering.

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