Constructing the class while traversing list of pre-import(script.src) promise is wrong. This make some logic that involve slot attribute being buggy. All class module should be instantiated at the same time right after shadow.append(...host.children). It also prevent some unknown ES modules to traverse element outside the host.
Note when wait attributes #6 detected, it will inject :root { display: none } into shadow root style sheet and remove that style rule when all waited classes instantiated.
Constructing the class while traversing list of pre-
import(script.src)promise is wrong. This make some logic that involveslotattribute being buggy. All class module should be instantiated at the same time right aftershadow.append(...host.children). It also prevent some unknown ES modules to traverse element outside the host.