[RFC]elements schema: add support for custom schemas

in @Compoent, schemas can currently only use the following values:

• CUSTOM_ELEMENTS_SCHEMA -> allow any custom-tag with any property,
• NO_ERRORS_SCHEMA -> allow any tag and any property

We need to implement a way to defined custom schemas, ie defining all polymer elements and their properties (and events).

@mprobst when would you be available so that we can discuss how to integrate with the security schema ?

[sijakret]

This issue has been around since 2016, is not hard to fix and would help EVERY angular project that uses web components. To me it feels like it is strategically ignored to keep up lock in.

[sijakret]

is there any reason to not just provide a way to customize the following checks? https://github.com/angular/angular/blob/b5ab7aff433a67cddaa55e621d17b1a1b07b57c2/packages/compiler/src/schema/dom_element_schema_registry.ts#L294 https://github.com/angular/angular/blob/b5ab7aff433a67cddaa55e621d17b1a1b07b57c2/packages/compiler/src/schema/dom_element_schema_registry.ts#L315

if these were pluggable users could already significantly refine which tags to bail out on. this would already be much better than just dropping everything when CUSTOM_ELEMENTS_SCHEMA is used

if i patch my local compiler with 3 lines i can get immediately it to do what i need!