Updating input variable not triggering observeEvent if new value is the same

shiny
10

Hi,

The code still suffers from the same problem, meaning that it will execute the output$output1 <- renderTable twice when you change input1 and you have a different input2 (plust the code starts with an error message, but that's besides the point).

So, if the app is running and input1 = file1 and input2 = bread, and you change input1 to file2, the code is run once. But, if input1 = file1 and input2 = oranges and you change input1 to file2, the code is run twice.

Again, the main question I have is just why explicitly updating a reactive variable to the same value is not triggering it.

Here is another reprex:

library(shiny)

ui <- fluidPage(
  
  numericInput("input1", "Set a value", value = 0),
  actionButton("click", "Click")
  
)

server <- function(input, output, session) {
  
  myVal = reactiveVal()
  
  observeEvent(input$click, {
    print("click registered")
    myVal(input$input1)
  }, ignoreInit = T)
  
  observeEvent(myVal(), {
    showModal(modalDialog("Update"))
  }, ignoreInit = T)
  
}

shinyApp(ui, server)

If you click the button once after you changed the value, there will be a pop-up. But if you click the button again, nothing will happen, although in the code the value gets updated explicitly (with the same value)

It's really a theoretical question. I know you can solve this by putting the modal in the first observeEvent that looks for the click, but the point is that I don't get it why the value wont trigger reactivity if it gets updated with the exact same value.

In my real example, there is a lot more going on and there is need to have two separate observeEvents so I can't merge them. If I do, I end up with the double execution again.

Don't worry, I did find a workaround with some additional variables, but I just would like to know why this isn't updating the way you'd expect.

PJ

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