feat: improve Typescript support for exactOptionalPropertyTypes

[aeharding]

Prerequisites

• I have read the Contributing Guidelines.
• I agree to follow the Code of Conduct.
• I have searched for existing issues that already include this feature request, without success.

Describe the Feature Request

exactOptionalPropertyTypes makes TypeScript truly enforce the definition provided matches the actual javascript value.

It's a recently added feature (v4.4) that is increasing in use.

However, many of Ionic's types are incompatible with exactOptionalPropertyTypes. This is because they define types as this:

  "shape"?: 'round';

and not this:

  "shape"?: 'round' | undefined;

It is worth noting that core React types follow the latter convention. Example:

Describe the Use Case

See above.

Describe Preferred Solution

Unless there is a specific reason, all Ionic attributes with ? also list undefined as an explicit accepted value.

Describe Alternatives

Not using exactOptionalPropertyTypes will opt the user out of many benefits, but it is a workaround for now.

Related Code

No response

Additional Information

This could also be considered a bug for certain attributes, since certain types, like className defined here don't actually conform with the React className attribute: