Separate `renderUI` in a module server - nested namespaces

[saturne]

Hello,

In some complex and large shiny apps, the UI parts are often rendered with renderUI and uiOutput. Consider this small one for illustration:

modUI <- function(id) {
  ns <- NS(id)
  uiOutput(ns("theUI"))
}

modServer <- function(id) {
  moduleServer(
    id, 
    function(input, output, session) {
      
      output[["plot"]] <- renderPlot({
        n <- input[["numb"]]
        plot(rnorm(n), rnorm(n), pch = 19L)
      })
      
      ns <- session$ns
      output[["theUI"]] <- renderUI({
        tagList(
          sliderInput(ns("numb"), "N", 10, 100, 50),
          plotOutput(ns("plot"))
        )
      })
    }
  )
}

ui <- basicPage(
  br(),
  modUI("myapp")
)

server <- function(input, output, session) {
  modServer("myapp")
}

Here modUI is ridiculously small. But in modServer, the renderUI could be large and there could be many other output components. Therefore it is desirable to split modServer:

renderPlotServer <- function(id) {
  moduleServer(
    id, 
    function(input, output, session) {
      
      output[["plot"]] <- renderPlot({
        n <- input[["numb"]]
        plot(rnorm(n), rnorm(n), pch = 19L)
      })
      
    }
  )
}

renderUIServer <- function(id) {
  moduleServer(
    id, 
    function(input, output, session) {
      
      ns <- session$ns
      output[["theUI"]] <- renderUI({
        tagList(
          sliderInput(ns("numb"), "N", 10, 100, 50),
          plotOutput(ns("plot"))
        )
      })
      
    }
  )
}

and to put them together one can use the same id:

modServer <- function(id) {
  moduleServer(
    id, 
    function(input, output, session) {
      renderPlotServer("mysubapp")
      renderUIServer("mysubapp")
    }
  )
}

but then we need a nested namespace in the UI part of the module:

modUI <- function(id) {
  ns <- NS(NS(id)("mysubapp"))
  uiOutput(ns("theUI"))
}

Do you agree or am I overcomplicating something? Is there a simpler way?

I prefer to wait for some reactions before sharing my other thoughts...

[saturne]

A simpler way, to avoid the nested namespace, would be:

modServer <- function(id) {
  moduleServer(
    id, 
    function(input, output, session) {
      renderPlotServer(NULL)
      renderUIServer(NULL)
    }
  )
}

Is it a good practice?

[saturne]

I think the NULL namespace is not a good practice, because it prevents to use the module multiple times.