@ContentChildren not populating from parent <ng-content>

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[ ] feature request
[ ] support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior @ContentChildren does not seem to work on Parent <ng-content> containers. Even if the ng-content is a child of the component.

Expected behavior I expect that ContentChildren is filled if it is a child of the component

Minimal reproduction of the problem with instructions https://plnkr.co/edit/J5itJmDfwKwtBsG6IveP?p=preview

Main HTML:

<div>
  <child>
    <test></test>
    <test></test>
    <test></test>
  </child>
  <br><br>
  <parent>
    <test></test>
    <test></test>
    <test></test>
  </parent>
</div>

Child Component:

<h2>Child</h2>
<parent>
  <ng-content></ng-content>
</parent>

Parent Component:

<h3>Parent</h3>
<ng-content></ng-content>
<div class='length'>Line count : {{length}}</div>

Please tell us about your environment: Windows, Angular4

[ReneWerner87]

bug is still open in angular 9 and 10 … please solve it

[mkurcius]

Any news on this?