why "optional" in share(optional ShareData data)?

[marcoscaceres]

Given that the first thing we need to check is if data has some members, shouldn't the share() signature actually make data required?

Alternatively, the method signature should default to the empty dictionary:

[SecureContext] Promise<void> share(optional ShareData data = {});

However, I think we should just make data required.

[ewilligers]

See the first note in https://wicg.github.io/web-share/level-2/#navigator-interface

The data argument is marked as "optional", but it is effectively required; share() will return a rejected promise with a TypeError if called with no arguments. WebIDL mandates that it be optional because the dictionary members are all optional. See WebIDL Issue #130.

https://heycam.github.io/webidl/#idl-operations

If the type of an argument is a dictionary type or a union type that has a dictionary type as one of its flattened member types, and that dictionary type and its ancestors have no required members, and the argument is either the final argument or is followed only by optional arguments, then the argument must be specified as optional and have a default value provided.

We should add = {}