Additonal schema with predefined non-angular elements

[BaerMitUmlaut]

🚀 feature request

Relevant Package

This feature request is for @angular/core

Description

Currently there are two schemas available to allow non-angular custom elements and attributes:

• CUSTOM_ELEMENTS_SCHEMA - ignores everything unknown
• NO_ERRORS_SCHEMA - allows anythin dash-cased

However, there is no way to limit the allowed elements any further or to specify a number of allowed elements, for example to check for typos.

Describe the solution you'd like

I'd expand the SchemaMetadata interface like this:

export interface SchemaMetadata {
  name: string;
  tokenValid?: (token: string) => boolean;
}

The functions would check if the given token (element or attribute name) is valid, it's optional for full backwards compatibility (though that's probably not even necessary). Alternatively this could be split into two functions (attributeValid & elementValid).

Then there could be a class or helper function that generates an object which simply checks if the given token is within a set of previously defined tokens.

This would also clean up existing code because you don't have to hardcode the logic of the schema everywhere it's used.

If you approve, I can implement this and PR, should be pretty simple.

[lacolaco]

this is similar to #12045.

[BaerMitUmlaut]

Oh I'm sorry, didn't find that one, looks like I made a duplicate. I will post my suggestion over there.

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