R Shiny: Nested tabPanels disable each other - r

Question

In the attached MWE Shiny example, I have a nested tabsetPanel within a tabPanel for a navbar. If you run the MWE with only one tabPanel within the tabSet you will see that Shiny behaves exactly as it is expected. However, if you run the MWE with two tabPanels, the result is not printed to the main panel of each tab.
Why does this behaviour occur? And how do I resolve this conundrum?
library(shiny)
ui <- shinyUI(navbarPage("tabalicious",
tabPanel("Nav1", value = "nav1",
mainPanel(h2("Hello"),
br(),
p("This is my app.")
)
)
,
tabPanel("Nav2", value = "nav2",
tabsetPanel(
tabPanel("tabsettab1",
sidebarLayout(
sidebarPanel(
helpText("Choose your settings"),
selectInput("zone_type",
label = "Choose a zone type to display",
choices = list("Industrial", "Residential"),
selected = "Industrial")
),
mainPanel(h2("A tab for a tabSet"),
textOutput('zone_type')
)
)
)
# Uncomment this to see the issue
# ,
# tabPanel("tabsettab2",
# sidebarLayout(
# sidebarPanel(
# helpText("Choose your settings"),
# selectInput("zone_type",
# label = "Choose a zone type to display",
# choices = list("Industrial", "Residential"),
# selected = "Industrial")
# ),
# mainPanel(h2("A tab for a tabSet"),
# textOutput('zone_type')
# )
# )
# )
)
)
)
)
server <- shinyServer(function(input, output) {
output$zone_type <- renderText({
paste("You have selected", input$zone_type)
})
})
# Run the application
shinyApp(ui = ui, server = server)

Answer 1

It doesn't have to do with tabs, but multiple calls to output the results of the same render* function. For example, a simplified page (with no tabs) will work fine, but if you uncomment the duplicated call, will fail to display zone_type:
library(shiny)
server <- shinyServer(function(input, output) {
output$zone_type <- renderText({paste("You have selected", input$zone_type)})
})
ui <- shinyUI(fluidPage(
selectInput("zone_type",
label = "Choose a zone type to display",
choices = list("Industrial", "Residential")),
# textOutput('zone_type'),
textOutput('zone_type')
))
runApp(shinyApp(server = server, ui = ui))
While your shinyUI function can only call each output of shinyServer once, within shinyServer you can call the inputs as many times as you like, so it's easy to duplicate outputs:
library(shiny)
server <- shinyServer(function(input, output) {
output$zone_type <- renderText({paste("You have selected", input$zone_type)})
output$zone_type2 <- renderText({paste("You have selected", input$zone_type)})
})
ui <- shinyUI(fluidPage(
selectInput("zone_type",
label = "Choose a zone type to display",
choices = list("Industrial", "Residential")),
textOutput('zone_type'),
textOutput('zone_type2')
))
runApp(shinyApp(server = server, ui = ui))
If you don't want to duplicate work for the server, you can't pass one output to another, but you can just save the render* results to a local variable which you can pass to both outputs:
server <- shinyServer(function(input, output) {
zone <- renderText({paste("You have selected", input$zone_type)})
output$zone_type <- zone
output$zone_type2 <- zone
})