I suppose you could fall back on the History module and use History.setPath, History.replacePath or possibly History.setHash (in the latest version), depending on whether you want to generate a history entry or not.

That is, the location2action for "" would not show the page directly ... instead, it would return a different action that would use one of the History methods (as an effect) to set the URL you want. That, in turn, would trigger a second round of location2action, which would now be for "home", which you'd handle normally.

At least, I think that sort of thing ought to work -- I haven't tried it lately.

The other possible approach would be to do something with deltaToUpdate that returns a HashUpdate to the desired URL. However, I have a feeling that might not work, because I think I disabled deltaToUpdate while processing the actions returned by location2action ... I was getting some infinite loops otherwise.

Thanks @rgrempel !

I have succeeded:

type Action 
  = ...
  | Redirect String
  | NoOp

location2action list = 
  case list of
    [ "" ] ->
      [ Redirect "home"]

update action model =
  case action of

    Redirect url ->
      ( model, History.replacePath (prefix ++ url) |> Task.map (\()-> NoOp) |> Effects.task)