R Shiny module: input not updated with uiOutput / renderUI inside callModule - r

Question

I've been searching around and cannot find an answer to my question. I've constructed a simple app to demonstrate my problem. Basically, the problem is that I am trying to use a renderUI inside my module server to conditionally create a uiOutput in the module UI. I've included a few print statements that lead me to believe that the renderUI is evaluated without input being updated. It is killing me that I can't figure this out, and I'd appreciate any help possible!
Example code:
library(shiny) # shiny_1.0.0
library(DT) # DT_0.2
testModuleUI <- function(id) {
ns = NS(id)
tagList(
br(),
sidebarPanel(width = 12, id = "inputBar",
fluidRow(
column(width = 2, checkboxInput(ns("buttonA"), label = "Button A", value = F)),
column(width = 2, uiOutput(ns("getButtonB")))
),
dataTableOutput(outputId = ns("tableOutput"))
)
)
}
testModule <- function(input, output, session, showB = F ){
ns = session$ns
output$getButtonB <- renderUI({
if( showB ){
print("call checkboxInput")
checkboxInput(ns("buttonB"), label = "Button B", value = F)
}else{
NULL
}
})
getTable <- reactive({
print("inside getTable")
out = c()
if( input$buttonA ) {
out = paste0(out, "A")
}
if( input$buttonB ){
out = paste0(out, "B")
}
data.frame(var = out)
})
output$tableOutput <- renderDataTable({
print("call getTable")
datatable( getTable() )
})
}
server <- function(input, output, session) {
callModule( module = testModule, id = "test1", showB = T )
session$onSessionEnded( stopApp )
}
ui <- pageWithSidebar(
headerPanel( title = "Test app" ),
sidebarPanel(
width = 3,
selectInput(inputId = "whatever", label = "This button doesn't matter", choices = c("A", "B"))
),
mainPanel(
tabsetPanel(
tabPanel("Tab 1", testModuleUI("test1"))
)
)
)
shinyApp( ui = ui, server = server, options = list(launch.browser = T)
)
Thank you!!