promises support for new shiny async

[fabiangehring]

Shiny supports async evaluation in it's current dev (async branch merged a few days ago). Plotly does not seem to support this new functionaility yet.

The error of the following minimal app says: "no applicable method for 'ggplotly' applied to an object of class "promise""

library(shiny)
library(plotly)
library(promises)
library(future)
plan(multiprocess)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      sliderInput("n",
                  "Test:",
                  min = 1,
                  max = 50,
                  value = 30)
    ),
    
    mainPanel(
      plotlyOutput("plot")
    )
  )
)

server <- function(input, output) {
  getData <- function(n) {
    data.frame(x = sample(n), y = sample(n))
  }
  
  data <- reactive({
    n <- input$n
    future(getData(n))
  })
 
  output$plot <- renderPlotly({
    data() %...>%
      plot_ly(x = ~x, y = ~y)
  })
}

shinyApp(ui = ui, server = server)