R Shiny, shinyapps.io printing error messages for R codes

Question

I was trying to create a Shiny app that takes code blocks and runs the code then gives the output for that code block.

To do that I take a textInput, then with the following, tried to provide outputs for users.

Question1 <- reactive({
    eval(parse(text=input$Question1_code))
})

output$Question1_output <- renderText({
    input$Run_Code
    isolate(paste(Question1()))
})

Now, my problem is when I run this on locally, the output I get for wrong statements/codes e.g.

seq(1,10,-2)

is wrong sign in 'by' argument. (which is what I would like to see for a wrong statement)

However, when I run it on shinyapps.io, I get the following error message,

An error has occurred. Check your logs or contact the app author for clarification.

How can I print the same error message that I am getting locally (wrong sign in 'by' argument) on shinyapps.io too?

Answer 1

use shinyCatch from spsComps

Example for your case:

library(shiny)
library(spsComps)
ui <- fluidPage(
  actionButton("a", "blocking"),
  actionButton("b", "no blocking"),
)

server <- function(input, output, session) {
    observeEvent(input$a, {
      spsComps::shinyCatch({
          seq(1,10,-2)
      },
      # blocking recommended
      blocking_level = "error",
      prefix = "My-project" #change console prefix if you don't want "SPS"
      )
      # some other following actions will NOT  be run 
      print("other actions")
    })
    
    # if you dont want to block
    observeEvent(input$b, {
        spsComps::shinyCatch({
            seq(1,10,-2)
        }, prefix = "My-project")
        # some other following actions will run 
        print("other actions")
    })
}

shinyApp(ui, server)

or try more demos here