Hello,

I’m a bit at a loss with file uploads in Phoenix liveview. Everything works great, except that when I get validation errors I am unable to assign a value inside the socket. I have a custom progress handler (which also works just fine), but when user tries to upload too many files at once, I would like to cancel the uploads and set :upload_progress back to 0. Not only is there some initial progress, but I’m also unable to reset it back to 0. I see the flash error but assign() seems to do nothing here.

  @impl true
  def handle_event("validate", _params, %{assigns: assigns} = socket) do
    photoset = assigns.uploads.photoset
    {:noreply, socket |> update_socket_based_on_errors(photoset)}
  end

  defp update_socket_based_on_errors(socket, photoset) do
    if !Enum.empty?(photoset.errors) do
      Enum.reduce(photoset.errors, socket, fn error, acc_socket ->
        handle_error(error, acc_socket)
      end)

      Enum.each(photoset.entries, &cancel_upload(socket, :photoset, &1.ref))
      socket |> assign(:upload_progress, 0) # this doesn't update the HTML correctly, no error is thrown.
    else
      socket
    end
  end

  defp handle_error({picture, :too_large}, socket) do
    socket
    |> put_flash!(:error, "File size of photo #{picture} is too large")
  end