Proposal: A new way to do feature detection for members

[beaufortfrancois]

Web APIs are relying more and more on dictionaries. And doing feature detection of such members requires ugly and unnecessary complicated code. Following WICG/EventListenerOptions#31, #491, and many more over the years, I'm proposing WebIDL allows us to expose interfaces under a specific "namespace/scope" to avoid polluting the global scope.

Current state for an API called MyAPI

1. A dictionary makes it unnecessarily hard to detect its members.

dictionary MyDictionaryOptions {
  boolean foo;
};

2. An interface pollutes global scope as window.MyDictionaryOptions now unnecessarily exists.

[Exposed=Window]
interface MyDictionaryOptions {
  boolean foo;
}

Proposal

Use interfaces instead of dictionaries when possible and expose them under a specific member of the API.

[Exposed=Window.MyAPI] // <-- NEW!
interface MyDictionaryOptions {
  boolean foo;
}

if ("foo" in window.MyAPI.MyDictionaryOptions) {
  // 1. It's easy to detect foo exists in MyDictionaryOptions 
  // 2. Detecting it does not pollute global scope
  // 3. It does not require executing some methods to test it.
}

What do you folks think about this?

[annevk]

Why would we not continue the discussion in whatwg/webidl#107?

[eladalon1983]

Why would we not continue the discussion in whatwg/webidl#107?

Do you mean to say that you'd like to conclude the discussion on whatwg/webidl#107 first? Or move the issues to that repo? Or that you would like François and I to both copy/paste our proposals into that specific thread as-is and continue there?

[annevk]

Primarily the first. And I recommend not focusing on specific solutions for now.