Extended task example app

app.R

library(shiny)
library(bslib)
library(future)
library(promises)

future::plan(future::multisession)

ui <- page_sidebar(
  sidebar = sidebar(
    numericInput("x", "x", 5),
    numericInput("y", "y", 6),
    input_task_button("calc", "Calculate", type = "primary"),
    p(
      strong("Status: "),
      textOutput("status", inline = TRUE)
    ),
  ),
  h4("x * y (fast)"),
  verbatimTextOutput("result_fast"),
  h4("x + y (extended/slow)"),
  verbatimTextOutput("result", placeholder = TRUE)
)

server <- function(input, output, session) {
  adder_task <- ExtendedTask$new(function(x, y) {
    # This line would throw!
    # input$x

    future_promise({
      Sys.sleep(3)
      x + y
    })
  }) |> bind_button_to_task("calc")

  observeEvent(input$calc, {
    adder_task$invoke(input$x, input$y)
  })

  output$status <- renderText({
    adder_task$status()
  })

  output$result <- renderText({
    adder_task$result()
  })

  output$result_fast <- renderText({
    input$x * input$y
  })
}

shinyApp(ui, server)

Line 33 should be
}) |> bind_task_button("calc")