Give warning when runApp is called within runApp

[burgerga]

EDIT: sorry, figured out the real problem, the 'Run App' button calls runApp with as argument the directory, however if you have an app.R with some custom shinyApp calls it fails. So in the example below if you simple select all and execute, it works fine. But you should not use the 'Run App' button.

In the documentation for shinyApp one of the examples shows how to make a shinyApp from an 'an explicit UI/server pair', however this example doesn't work. The example in question is

app <- shinyApp(
  ui = fluidPage(
    numericInput("n", "n", 1),
    plotOutput("plot")
  ),
  server = function(input, output) {
    output$plot <- renderPlot( plot(head(cars, input$n)) )
  }
)

runApp(app)

which fails with

Listening on http://127.0.0.1:3280
Warning: Error in handlers$add: Key / already in use
Stack trace (innermost first):
    43: handlers$add
    42: handlerManager$addHandler
    41: startApp
    40: runApp
     1: shiny::runApp
Error in handlers$add(handler, key, tail) : Key / already in use

[wch]

This works fine for me. I've seen that error before when reloading shiny in a development session. If you used install_github, something similar may have happened. Try restarting your R session and running it again.

[wch]

Oh wait, I just saw your edit. So you're calling runApp() inside of another runApp()? If that's the case, we could provide a more informative error message.

[burgerga]

Yes, I think that's what's happening. Would also explain the error the error message, since / is the default argument for uiPattern and then it tries to start 2 apps, both with uiPattern = "/". But I agree that the error could be clearer.

PS What I ended up doing is renaming the file (no longer app.R), then the button goes away ;)