App that shows catching of duplicate IDs across static and dynamic UI

library(shiny)

ui <- fluidPage(
    sidebarLayout(
        sidebarPanel(
            sliderInput("bins",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30),
            checkboxInput("showDynamicPlot", "Show dynamic plot")
        ),
        mainPanel(
           plotOutput("distPlot"),
           # Uncomment this line to trigger initialization duplicate error
           # plotOutput("distPlot", width = "50%"),
           uiOutput("dynamicPlot"),
        )
    )
)

server <- function(input, output) {

    output$distPlot <- renderPlot({
        x    <- faithful[, 2]
        bins <- seq(min(x), max(x), length.out = input$bins + 1)

        hist(x, breaks = bins, col = 'darkgray', border = 'white',
             xlab = 'Waiting time to next eruption (in mins)',
             main = 'Histogram of waiting times')
    })

    output$dynamicPlot <- renderUI({
      if (input$showDynamicPlot) {
        sliderInput("bins",
          "Number of bins:",
          min = 1,
          max = 50,
          value = 30)
      }
    })
}

shinyApp(ui = ui, server = server)

Hello @nstrayer, great addition - it certainly has the potential to reduce confusion occasionally. I'm curious, though: could there be a feature to switch this off, perhaps through a setting, for instances where it might be preferable to keep it concealed in a production environment?

Best,
Michael

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Hello @nstrayer, great addition - it certainly has the potential to reduce confusion occasionally. I'm curious, though: could there be a feature to switch this off, perhaps through a setting, for instances where it might be preferable to keep it concealed in a production environment?

Best, Michael

Hi Michael,

This is a good point. Right now this only should catch errors that would have otherwise broken your app. We're going to try bringing it in where it is always active and then run our large suite of tests on Shiny to see if we're going to start causing spurious error messages to appear. If it becomes a problem then the plan would be to make it only show up when devmode is turned on for Shiny.

In 34cf27e, I switched where the logic for throwing on duplicate ID bindings was. Now we let Shiny run through all the input and output bindings. Then after both bindInputs() and bindOtuputs() have run, we validate and throw a much more helpful error message that contains all the duplicates. This means we can get error messages like this:

The following IDs were repeated: 
"vars": (2 inputs and 1 output), 
"bins": (2 inputs)

This is what the current error messages look like, since the previous screenshots are out-of-date: