Why does compiling angular dependencies from es2015 to esm2015 remove html tags in environment?

Question

As soon as the generating browser application bundle is over intellij can't resolve the html tags anymore. Why is that?

Also i found out if i don't add the AngularMaterialModule to the AppModule i keep all angular material html tags.

Compiling @angular/cdk/accordion : es2015 as esm2015

Compiling @angular/material/expansion : es2015 as esm2015

Compiling @angular/common/http : es2015 as esm2015

Compiling @angular/material/icon : es2015 as esm2015

Compiling @angular/cdk/text-field : es2015 as esm2015

Compiling @angular/material/input : es2015 as esm2015

Compiling @angular/material/list : es2015 as esm2015

Compiling @angular/material/menu : es2015 as esm2015

Compiling @angular/material/select : es2015 as esm2015

Compiling @angular/cdk/layout : es2015 as esm2015

Compiling @angular/material/tooltip : es2015 as esm2015

Compiling @angular/material/paginator : es2015 as esm2015

Compiling @angular/material/progress-spinner : es2015 as esm2015

Compiling @angular/material/sidenav : es2015 as esm2015

Compiling @angular/material/snack-bar : es2015 as esm2015

Compiling @angular/material/sort : es2015 as esm2015

Compiling @angular/cdk/table : es2015 as esm2015

Compiling @angular/material/table : es2015 as esm2015

Compiling @angular/material/tabs : es2015 as esm2015

Compiling @angular/material/toolbar : es2015 as esm2015

Compiling @angular/material/tree : es2015 as esm2015

Compiling @angular/material/badge : es2015 as esm2015

Compiling @angular/material/grid-list : es2015 as esm2015

Compiling @angular/material/radio : es2015 as esm2015

Compiling @angular/material/datepicker : es2015 as esm2015

Unknown html tag

Answer 1

Must be WEB-50675, it's fixed in upcoming 2021.1.2 update