Mandate a default value for boolean dictionary members?

[saschanaz]

What is the issue with the Web IDL Standard?

It's very easy to just write boolean foo; in dictionaries even when it's not really expected to be tristate.

There are certainly intentional tristate booleans like passive of EventListenerOptions, but maybe we should guide the new specs to use enums for such multistate instead or use nullable booleans (boolean? foo = null)?

(I don't have a definite list of accidental tristate booleans in specs, for now this is just what I observed when dealing with Gecko IDL.)

[annevk]

I kinda like this idea, but how would we enforce it? We'd need to syntactically distinguish the intentional tri-state booleans somehow.

(https://dom.spec.whatwg.org/#dictdef-mutationobserverinit is also a valid use of tri-state booleans, in my opinion.)

[saschanaz]

I'm thinking of making the validator fail unless there's some extattr like [TriState] boolean foo;