Pregunta

¿Por qué unsliderInput() que se genera en elserver, y prestados en elui conuiOutput() no se muestra en unmenuItem()?

Ejemplo

En esta sencilla aplicación estoy generando unsliderInput sobre elserver (nota lamenuItem está deliberadamente comentado), y funciona como se esperaba

library(shiny)
library(shinydashboard)

rm(ui, server)

ui <- dashboardPage(
    dashboardHeader(),

    dashboardSidebar(
        sidebarMenu(
            #menuItem(text = "data options",
                      checkboxGroupInput(inputId = "cbg_group1", label = "group 1", 
                                         choices = c("some","check","boxes","to","choose","from") ),
                       uiOutput("sli_val1"),
                       checkboxGroupInput(inputId = "cbg_group2", label = "group 2", 
                                          choices = c("another","set","of","check","boxes") ),
            #                ),
            menuItem(text = "another tab")
            )
    ),
    dashboardBody()
)

server <- function(input, output, session){

    withProgress(message = "loading page", value=0.1, {
        ## simulate loading some data
        Sys.sleep(3)

        ## slider input
        output$sli_val1 <- renderUI({
            sliderInput(inputId = "sli_val1", 
                        label = "values", min = 0, max = 100,
                        value = c(25, 75) )
        })
        setProgress(value=1, detail="Complete")
    })
}

shinyApp(ui = ui, server = server)

Sin embargo, cuando muevo eluiOutput dentro de unamenuItem( ), la salida ya no representa:

ui <- dashboardPage(
    dashboardHeader(),

    dashboardSidebar(
        sidebarMenu(
            menuItem(text = "data options",
                     checkboxGroupInput(inputId = "cbg_group1", label = "group 1", 
                                        choices = c("some","check","boxes","to","choose","from") ),
                     uiOutput("sli_val1"),
                     checkboxGroupInput(inputId = "cbg_group2", label = "group 2", 
                                        choices = c("another","set","of","check","boxes") )
                             ),
            menuItem(text = "another tab")
            )
    ),
    dashboardBody()
)