Context: Omit as prop in types

[mirka]

Description

This is an attempt to actually omit the as prop from WordPressComponentProps when polymorphism is disabled.

Given some code like this with a component flagged as non-polymorphic:

// some-file.tsx
const InvalidDivider = () => <Divider as="a" />;

The current implementation still acknowledges as as an actual prop type, only that it has to be undefined. This will cause some docgens to list as as a member of the props. It also gives us a TS error like this:

Type 'string' is not assignable to type 'undefined'.

Whereas, if it were any other non-existent prop, it should give you an error like:

Type '{ as: string; }' is not assignable to type 'IntrinsicAttributes & Props & Omit<Pick<DetailedHTMLProps<HTMLAttributes<HTMLHRElement>, HTMLHRElement>, "key" | keyof HTMLAttributes<...>> & { ...; }, "as" | ... 1 more ... | keyof Props>'.

Property 'as' does not exist on type 'IntrinsicAttributes & Props & Omit<Pick<DetailedHTMLProps<HTMLAttributes<HTMLHRElement>, HTMLHRElement>, "key" | keyof HTMLAttributes<...>> & { ...; }, "as" | ... 1 more ... | keyof Props>'.

I'm not 100% sure if the approach in this PR is the best way to achieve it though. Let me know if there are better ways.

Testing Instructions

1. In some .tsx file, add a code snippet like const InvalidDivider = () => <Divider as="a" /> for a non-polymorphic component. It should give you the expected TS error.
2. Similarly, try a snippet like const ValidSpacer = () => <Spacer as="aside" /> for a polymorphic component. It should not emit TS errors.

Types of changes

New feature

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).
• I've updated related schemas if appropriate.

[sarayourfriend]

I don't know why this wasn't the original solution to begin with 🤦 Thank you for noticing this improvement! It makes a lot more sense and the types are easier to understand this way too.