ElmでpreventDefaultなフォームを作る

Elmのバージョンは0.19
以下の onSubmitWithPrevented のような関数を定義すればよい。

import Json.Decode as JD

-- 省略...

onSubmitWithPrevented msg =
    Html.Events.custom "submit" (JD.succeed { message = msg, stopPropagation = True, preventDefault = True })

view : Model -> Browser.Document Msg
view model =
  {
    title = "Simple form example",
    body = [
      Html.form [onSubmitWithPrevented StartsLoggingIn] [
        div [] [
          label [] [
            text "email:",
            input [type_ "email", placeholder "Your email", value model.newLogin.email, onInput UpdatesLoginEmail] []
          ]
        ],
        div [] [
          label [] [
            text "password:",
            input [type_ "password", placeholder "Your password", value model.newLogin.password, onInput UpdatesLoginPassword] []
          ]
        ],
        div [] [
          button [] [text "login"]
        ]
      ]
    ]
  }

参考: https://stackoverflow.com/questions/52541501/why-cant-i-use-onwithoptions-in-elm-0-19