Handling dependencies not specified in the IDL

[danyao]

I'm using webidl2js to generate JavaScript interfaces for web API polyfills. My IDL may depend on other interfaces that are already natively supported in a browser. webidl2js seems to expect to be part of a complete system generating all dependent interfaces from scratch. So it generate require statements for these dependent interfaces as well.

Manually removing the require statements from the generate JS is not a full solution because there are accesses to <DependentType>.interface.prototype and built-in types don't have the interface field.

Perhaps webidl2js could assume any interfaces not specified in the IDL directory are provided already?

[TimothyGu]

With suppressErrors option and unknown types (types whose IDL definition is not available), no require statements are generated. For better support for interfaces not implemented through webidl2js, see #69.

[domenic]

@TimothyGu what happens to the output? Do we have tests? Do they use e.g. global.EventTarget or do they try to use global.EventTarget.interface? I'm not sure we should close this so hastily, although indeed suppressErrors might be the right answer.

[TimothyGu]

what happens to the output?

In @danyao's case I assume they add all the IDL fragments into webidl2js even for the interfaces not implemented with webidl2js. If only the IDL interfaces that are to be implemented with webidl2js are added to the transformer (as is the case for jsdom), we currently try to convert it by checking if the given object has our impl symbol, and if so unwrap the value using that symbol.

Do we have tests?

No, because our tests don't have suppressErrors enabled at the moment.

[danyao]

Our IDLs looked like this:

interface PaymentRequestUpdateEvent : Event {
    void updateWith(Promise<PaymentDetailsUpdate> detailsPromise);
};

PaymentRequestUdateEvent is to be implemented by webidl2js, but Event is already supported in the user agent natively. webidl2js generated JavaScript that looks like this:

const Event = require("./Event.js");
...
Object.setPrototypeOf(PaymentRequestUpdateEvent.prototype, Event.interface.prototype);

This results in two errors:

• require can't find "./Event.js"
• Event.interface.prototype fails because Event doesn't have an interface attribute.

[domenic]

Solving this would be helpful for the Streams Standard reference implementation, which runs its own webidl2js-generated code inside a jsdom environment, and would like to use that jsdom environment's AbortSignal. Currently the AbortSignal is not type-checked at all.