I am trying to make a shiny app that takes a numerical value that is used to filter a dataset and returns the filtered data as a table. I can get the app to do what I want, but when I insert validate() to be able to return a custom message when the filter input is not a valid value.
This is the code that I have:

in_data <- mtcars %>%
  distinct(hp, .keep_all = T) 

ui <- navbarPage("demo",
                 collapsible = T,
                 tabPanel("Cars One", uiOutput("page1")),
                 tabPanel("Car Tool", uiOutput("page2"))
)

server <- function(input, output){
  output$page1 <- renderUI({
    renderText('Page One')
  })
  
  output$page2 <- renderUI({
    fluidPage(
      sidebarLayout(
        sidebarPanel(
          numericInput(
            'input_hp', 'Enter HP:', 1, min = 1
          )
        ),
        mainPanel(
          DTOutput('car_spec')
        )
      )
    )
  })
  
  car_data <- reactive({
    in_data %>%
      filter(hp == input$input_hp) %>%
      t() 
      
  })
  
  output$car_spec <- DT::renderDT({
    # check that the hp is available
    validate(need(nrow(car_data()) < 1,
                  "Choose a different HP."))
    DT::datatable(
      car_data(),
      options = list(
        pageLength = 20,
        autoWidth = F,
        scrollX=T,
        dom = 't'
      ) # end of options
    ) 
  })
}

# Run the application
shinyApp(ui = ui, server = server)

I am using a toy dataset here (mtcars), but in reality, what I want to filter doesn’t have solid boundaries (besides being a positive integer). Using the above code, everything works as expected when I enter a valid value (93, for example). However, with the validate() portion, nothing updates even when I entered a valid value. My original app is a 2 pager with something else on the first page, so that’s why I have the first page here. Not really related to the issue.