Support different types of swapping?

[adithyaov]

hx-swap like feature may actually be very useful. Primarily to append a new
element to the list of elements.

Right now, since the entire hyperview is replaced, I have to think about the
entire view rather than just adding a new element at the end of a hyper view. I
also have to fetch the entire list again from my store on every addition.

In the Todo example, we do Todos.loadAll every time there is a SubmitTodo.

[seanhess]

Where would the right place to specify this behavior be? In the view or the handler?

[adithyaov]

If I've understood your question correctly, then the right place would be in the
handler.

The swap mode can be associated with the Action.

data Swap = InnerHTML | BeforeEnd

class (ViewId id, ViewAction (Action id)) => HyperView id es where

  data Action id

  swap :: Action id -> Swap
  swap _ = InnerHTML

I've not thought about the implementation-specific details. I can share a brief
write-up on how I would go about implementing it after finalizing how the usage
would look like.

---

So the usage would look like so:

instance (Todos :> es) => HyperView AllTodos es where
  type Require AllTodos = '[TodoView]

  swap SubmitTodo = BeforeEnd
  swap _ = InnerHTML

  data Action AllTodos
    = SubmitTodo
    | ...
    deriving (Generic, ViewAction)

  update action = do
    case action of
      SubmitTodo -> do
        TodoForm task <- formData @(TodoForm Identity)
        todoId <- Todos.create task
        pure $ displayTodo todoId
      ...

[seanhess]

I don't hate it, but this complicates the idea of what a HyperView is. Hyperbole is trying to give the developer an HTMX-like experience, but adds the concept of a typed HyperView to help organize the chaos. Forcing a simple model helps keep things sane as projects get big. Right now, the developer is guaranteed:

1. Any action the compiler allows is valid
2. The entire hyperview will be replaced
3. Using view functions, the view is only a function of its input state / data.

The only reason you would want to append is for performance, right? Imagine for a minute that there were no performance cost to re-rendering the whole view. There is great value in avoiding the need to track DOM state: if the view is always a function of the input, it's impossible for the data and the view to get out of sync.

Performance can be a real consideration, but preserving our sanity as developers is much more important. I don't think we can ignore the desire to append data forever, but we need a really clean way to do this that doesn't break what makes Hyperbole happy for developers. Let's wait until after our next release.