test if reactive value does not exist or is empty

I am trying to build an app that joins together different data sources conditional on user input. But I need to test the existence of reactives to do that, and can't figure it out.

I have one main dataset1 that I want to always pass back to the user (for a download, but here, a renderPrint) and then another dataset2 that I join to it, if it exists.

Here's a shiny reprex, key line at isTruthy:


app_ui <- function() {
    actionButton("get1", "Get dataset1"),
    actionButton("get2", "Get dataset2"),

app_server <- function(input, output) {
  dataset1 <-
    eventReactive(input$get1, {
      mtcars %>% head() %>% rowid_to_column()
  dataset2 <-
    eventReactive(input$get2, {
      chickwts %>% head() %>% rowid_to_column()
  dataset_joint <- reactive({
    if (isTruthy(dataset2())) {
      dataset1() %>%
    } else {
  output$view <-

shinyApp(app_ui, app_server)

I get the behavior I want if I replace isTruthy(dataset2()) with isTruthy(input$get2). But in my actual use-case, I am passing datasets between modules and testing the existence of a dataset is easier than passing around both the input and dataset and then testing the input.

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