title: Actionbutton stops display of datatable when file is uploaded for first time
body: <p>I have the shiny app below in which the user uploads a csv. Then the pickerInput gets the unique values of the first column of that csv and uses them to subset the dataframe and display it in a table. The issue is that I want to use an actionButton in order to apply changes but when the csv is uploaded for first time it should be displayed full and not displayed empty because the actionButton is not triggered yet. For the purpose of the example I have used <code>iris</code> dataset instead of a csv.</p>
  
  <pre><code># app.R ##
  library(shiny)
  library(DT)
  library(shinyWidgets)
  ui &lt;- pageWithSidebar(
    headerPanel('Iris k-means clustering'),
    sidebarPanel(
      fileInput("file1", "Choose CSV File",
                accept = c(
                  "text/csv",
                  "text/comma-separated-values,text/plain",
                  ".csv")
      ),
      uiOutput("id"),
  
      actionButton("go","Go")
    ),
    mainPanel(
      uiOutput('contents')
    )
  )
  
  server &lt;- function(input, output, session) {
    output$id&lt;-renderUI({
      #inFile &lt;- input$file1
      #df2&lt;-data.frame(read.csv(inFile$datapath, header = TRUE))
      pickerInput("select", "Select ID", 
                  choices = as.character(unique(iris$Species)), 
                  multiple = T,options = list(`actions-box` = TRUE),
                  selected = as.character(unique(iris$Species)))
    })
    output$contents &lt;- renderUI({
      input$goButton
      #inFile &lt;- input$file1
      #df&lt;-data.frame(read.csv(inFile$datapath, header = TRUE))
      df&lt;-data.frame(iris)
      df&lt;-subset(iris,Species %in% isolate(input$select))
  
        renderDataTable({
          datatable(
            df,
            options = list(scrollX = TRUE,pageLength=5)
          )
          })
  
    })
  }
  
  shinyApp(ui = ui, server = server)
  </code></pre>