shiny::downloadButton does not render in flexdashboard

rmarkdown

#1

I would like to include a download button in my flexdashboard, however shiny::downloadButton does not render while shiny::downloadLink does:


title: "Sidebar download button"
runtime: shiny
output:
flexdashboard::flex_dashboard:
orientation: columns
vertical_layout: fill

library(flexdashboard)

Column {.sidebar}

cars <- data("cars")

# renders

shiny::downloadLink(outputId = "save_link",
                    label = "Save cars.rds")

output$save_link <- downloadHandler(
    filename = function() {"cars.rds"},
    content = function(file) {
      saveRDS(cars, file)
    }
    )

# does not render

shiny::downloadButton(outputId = "save_button",
                    label = "Save cars.rds")

output$save_button <- downloadHandler(
    filename = function() {"cars.rds"},
    content = function(file) {
      saveRDS(cars, file)
    }
    )

Any help would be appreciated