Bug in shiny::updateCheckboxGroupInput()

If you want unselected all checkboxes defined using updateCheckboxGroupInput, the syntax should be:
updateCheckboxGroupInput(session, inputId, selected = NULL)

However, it does not work.
You must indicate again the parameter choices explicitly


Look at this code:

rm(list = ls())
library(shiny)

runApp(list(
  ui = basicPage(
    checkboxGroupInput('chkGrp', 
                       label="Choix", 
                       choices=list("A"="a", "B"="b", "C"="c", "D"="d", "E"="e")),
    actionButton("all","All"),
    actionButton("noneWithChoices","None With Choices"),
    actionButton("noneWithoutChoices","None Without Choices"),
    actionButton("partial","Partial"),
    verbatimTextOutput("value")
  ),
  server = function(input, output, session) {
    output$value <- renderPrint({ input$chkGrp })
    observe({
      if ( is.null(input$all) || input$all == 0)
        return()
      updateCheckboxGroupInput(session,"chkGrp", selected= letters[1:5] )
    })
    
    observe({
      if ( is.null(input$partial) || input$partial == 0)
        return()
      updateCheckboxGroupInput(session,"chkGrp", selected= c("a", "c") )
    })
    observe({
      if ( is.null(input$noneWithChoices) || input$noneWithChoices == 0)
        return()
      updateCheckboxGroupInput(session,"chkGrp", 
                               choices=list("A"="a", "B"="b", "C"="c", "D"="d", "E"="e"), 
                               selected=NULL)
    })
    observe({
      if ( is.null(input$noneWithoutChoices) || input$noneWithoutChoices == 0)
        return()
      updateCheckboxGroupInput(session,"chkGrp", 
                               selected=NULL)
    })
    
  }
))