Side effects stop working when runtime exception in subscribe

[WhileTruu]

If a runtime exception is caused in the subscribe function in js (such as calling an undefined function), commands are no longer being issued and subscriptions are ignored.

SSCCE

port module Main exposing (main)

import Browser
import Html exposing (Html, button, div, text)
import Html.Events exposing (onClick)
import Time


type alias Model =
    { time : Time.Posix }


initialModel : Model
initialModel =
    { time = Time.millisToPosix 0 }


type Msg
    = GotTime Time.Posix
    | ClickedCreateRuntimeExceptionInSubscribe


update : Msg -> Model -> ( Model, Cmd msg )
update msg model =
    case msg of
        GotTime time ->
            ( { model | time = time }, Cmd.none )

        ClickedCreateRuntimeExceptionInSubscribe ->
            ( model, createRuntimeExceptionInSubscribe () )


view : Model -> Html Msg
view model =
    div []
        [ div []
            [ text <| String.fromInt <| Time.toHour Time.utc model.time
            , text ":"
            , text <| String.fromInt <| Time.toMinute Time.utc model.time
            , text ":"
            , text <| String.fromInt <| Time.toSecond Time.utc model.time
            ]
        , button [ onClick ClickedCreateRuntimeExceptionInSubscribe ]
            [ text "create runtime exception in subscribe" ]
        ]


port createRuntimeExceptionInSubscribe : () -> Cmd msg


main : Program () Model Msg
main =
    Browser.element
        { init = \_ -> ( initialModel, Cmd.none )
        , view = view
        , update = update
        , subscriptions = \_ -> Time.every 1000 GotTime
        }

var app = Elm.Main.init({ node: document.querySelector('main') })
app.ports.createRuntimeExceptionInSubscribe.subscribe(() => yolo())

Expected

Subscriptions still update the model and cmds can still be issued through update.

Actual

Model can still be updated by user interactions, but subscriptions don't do anything and user interactions have no side effects.

• Elm: 0.19.0, elm-0.19.1-beta-1
• Browser: Chrome, Safari
• Operating System: MacOS, iOS

[rupertlssmith]

Been discussing this one on slack recently.

I think the call to the susbcription callback function is made here:

https://github.com/elm/core/blob/master/src/Elm/Kernel/Platform.js#L382

Will wrapping this in a try...catch block solve the problem? Have the catch block emmit an error message to the console if any unhandled exception falls through.

Another suggestion is to always use async:

myPort.subscribe(async (value) => {
       stuff();       
});

Can the Elm runtime always invoke the callback with async?

Which solution is better? Happy to make a PR for one.