Provide guidance on what to throw?

[marcoscaceres]

I'm wonder if the spec should provide some guidance on kind of DOM exception should be thrown?... we've got specs throwing:

• NotAllowedError (web share)
• SecurityError (Geolocation, Gamepad)
• Possibly others...

[clelland]

For existing features where policy control is being retrofitted, the current guidance (in integration.md) is

Existing web platform features which already have some mechanism for reporting errors, or signalling that the user chose not to grant permission, should use those existing mechanisms when disabled.

The goal there being to not break existing content by introducing a new failure mode, but instead have policy violations caught by existing error-handling code.

For new APIs, it's a different situation, for sure. We could provide some guidance, probably for both exception-based and promise-based APIs.

[marcoscaceres]

We could provide some guidance, probably for both exception-based and promise-based APIs.

That would be great. Personally, NotAllowedError in both cases would be fine:

[=throw=] a {{"NotAllowedError"}}` {{DOMException}}.

And:

Return [=a promise rejected with=] a {{"NotAllowedError"}} {{DOMException}}.