Delete corresponding input element when using removeUI

Question

Question

How do I delete/invalidate the corresponding input element, when deleting a control by removeUI?

You can see in the reprex below that even after the textInput is deleted, input$x is still 'truthy'. Ideally, I could tell shiny that input$x is not valid anymore and any reactives relying on input$x treat it as if empty.

Update

Reading the answers so far, I think I was not clear, what I want to achieve. I really want to know whether one can conceptually 'nullify' input$x. In this case I would not have to take any care that something would break down the line.

---

Reprex

library(shiny)

ui <- fluidPage(
  div(textInput("x", "Text"), id = "killme"),
  actionButton("del", "Delete"),
  verbatimTextOutput("out")
)

server <- function(input, output) {
  output$out <- renderPrint(req(input$x))
  observeEvent(input$del, removeUI("#killme"))
}

shinyApp(ui, server)

Answer 1

You could use reactiveValues for the printed output and assign it to NULL when deleting the div. I dont know if there is a more elegant solution.

library(shiny)

ui <- fluidPage(
  div(textInput("x", "Text"), id = "killme"),
  actionButton("del", "Delete"),
  verbatimTextOutput("out")
)

server <- function(input, output) {
  textX <- reactiveValues(x = NULL)

  observe({
    textX$x = input$x
  })

  observeEvent(input$del, {
    textX$x = NULL
    removeUI("#killme")
    })

  output$out <- renderPrint({
    req(textX$x)
    textX$x
    })
}

shinyApp(ui, server)

Answer 2

This SO question, shows how to nullify an input. With this the solution becomes:

ui <- fluidPage(
  tags$script("
    Shiny.addCustomMessageHandler('resetValue', function(variableName) {
      Shiny.onInputChange(variableName, null);
    });
  "),
  div(textInput("x", "Text"), id = "killme"),
  actionButton("del", "Delete"),
  verbatimTextOutput("out")
)

server <- function(input, output, session) {
  output$out <- renderPrint(req(input$x))
  observeEvent(input$del, {
    removeUI("#killme")
    session$sendCustomMessage("resetValue", "x")})

}

shinyApp(ui, server)

Thanks for the answers though, becuase only thanks to the discussion I could make my question clearer and was able to find the right solution.

---

Short form using library(shinyjs):

library(shiny)
library(shinyjs)

ui <- fluidPage(
  useShinyjs(debug = TRUE),
  div(textInput("x", "Text"), id = "killme"),
  actionButton("del", "Delete"),
  verbatimTextOutput("out")
)

server <- function(input, output, session) {
  output$out <- renderPrint(req(input$x))
  observeEvent(input$del, {
    removeUI("#killme")
    runjs('Shiny.onInputChange("x", null)')
  })

}

shinyApp(ui, server)