Bug 177722 – Support nullable and optional interfaces as members of a dictionary

• Status: NEW
• Component: Bindings

[Sam Weinig]

We currently treat a nullable interface that is an non-required member of a dictionary, just like we would a non-nullable interface that is an non-required member of a dictionary. That is for,

interface Test {
}

dictionary Foo {
    Test? test;
}

dictionary Bar {
    Test test;
}

Foo and Bar have the same backing struct:

struct Foo/Bar {
    RefPtr<Test> test;
}

To implement abort support for Fetch, we need to be able to distinguish these two cases to support the signal member on RequestInit (https://fetch.spec.whatwg.org/#requestinit) where differentiating between null and not-present is observable.

[Sam Weinig]

For more on why it is necessary, see https://github.com/whatwg/fetch/pull/523#discussion_r138886101