Add mapAsync

[zyla]

Asynchronous version of map, for easily integrating e.g. network requests into a FRP computation.

data AsyncComputation a = Sync a | Async (Aff a)

data AsyncState a
  = InProgress (Maybe (Either Error a))
  | Finished (Either Error a)

-- | Map a possibly-asynchronous function over a Dynamic.
-- |
-- | When the source dynamic changes, the mapping function is re-evaluated. If it returns `Sync`,
-- | this works like `map` - the change is propagated in the same cycle.
-- |
-- | If it returns `Async`, then the dynamic will first transition to `InProgress` and start the async computation.
-- | After it finished, it will transition to `Finished` (which might contain an error).
mapAsync :: forall a b. (a -> I.AsyncComputation b) -> Dynamic a -> Dynamic (I.AsyncState b)

[kozak]

LG.

[kozak]

Suggested change

	killFiber (error "Cancelled") fiber
	killFiber cancelledError fiber

[zyla]

Good catch. But I wonder why tests didn't catch it.

[kozak]

There are no tests for cancel I think.

[zyla]

No direct test, but this one should cancel the task internally

[zyla]

You're right, mapAsync doesn't call cancel, only run which calls killFiber directly. So this function is unnecessary