Parametrise EventListener

[zudov]

Since we provide types for various events (e.g. MessageEvent) it makes sense to have some way of using them in listeners.

Not quite sure, perhaps there is a better solution.

[garyb]

I had considered this too, but an alternative way: give EventType a phantom type variable.

I've not decided whether it's "too opinionated" to do so yet...

[zudov]

It would be nice to have what I've already commited and a phantom type variable to EventType. In that way event listeners would be able to handle arbitrary *Events, and EventTypes would be kept consistent with those *Events, when used with in things like addEventListener. Like so:

addEventListener :: forall eff ev. EventType ev -> EventListener ev (dom :: DOM | eff) -> Boolean -> EventTarget -> Eff (dom :: DOM | eff) Unit

[zudov]

Hmm. Looking at the table here
Some "Event Name"s (term used in the table) can have different "Event type"s. For example abort might be used in UIEvent, ProgressEvent or just Event. That means that we can't just say abort :: EventType ProgressEvent. It should be possible to express that table with type classes, but at that point it clearly gets opinionated.

Given that I think we'd have to leave addEventListener as it is without any restriction.

[zudov]

As for having EventListener :: * -> # ! -> *, here is an example of how I use it https://github.com/zudov/purescript-websocket-simple/blob/05dd8bdb6e4ca760851e0843040e3567b70feb38/src/WebSocket.purs#L105

[sharkdp]

(see also #23 for a workaround)

[zudov]

@sharkdp Oh, thanks for that reference. I should have checked existing issues :(

[garyb]

I don't think you need a class to express it, we'd just put the appropriate EventType smart constructor in a module for that event type.

I'll mock something up this weekend perhaps.