An extended HTML custom element is not activated when anything in that subtree is Blazor-controlled
- Dominant language
- C#
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Description
### Describe the bug
I have defined a HTML custom element that extends a built-in element. I can use this on pages, but only when the element or its children do not come in contact with Blazor in any way. This includes event handlers, interpolation (`Current count: @currentCount`) or referencing other components.
### To Reproduce
In the `index.html` of a new Blazor WASM project, I add
```html
window.customElements.define('my-custom-element', class MyCustomElement extends HTMLDivElement {
constructor() {
super();
console.log('instantiated');
}
}, { extends: 'div' });
```
to define a custom element that extends a `
In the `Counter.razor`, I can reference that component
```html
```
and the log message appears in the console.
However, as soon as I do something Blazory, the custom element is not instantiated anymore. All the following make the instantiation not happen:
```
```
### Further technical details
ASP.NET Core version 6 Preview 7
`dotnet --info`
```
.NET SDK (reflecting any global.json):
Version: 6.0.100-preview.7.21379.14
Commit: 22d70b47bc
Runtime Environment:
OS Name: Windows
OS Version: 10.0.19042
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.100-preview.7.21379.14\
Host (useful for support):
Version: 6.0.0-preview.7.21377.19
Commit: 91ba01788d
.NET SDKs installed:
5.0.400 [C:\Program Files\dotnet\sdk]
6.0.100-preview.3.21202.5 [C:\Program Files\dotnet\sdk]
6.0.100-preview.7.21379.14 [C:\Program Files\dotnet\sdk]
.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.29 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.29 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.18 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.0-preview.3.21201.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.0-preview.7.21378.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.29 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.18 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.0-preview.3.21201.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.0-preview.7.21377.19 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.18 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.0-preview.3.21201.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.0-preview.7.21378.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
```
- Visual Studio 17.0.0 Preview 3.1
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