Problem

I have a Shiny app in which I would like a selectInput to only take the unique values that are in the data. In the below example, even though Man is a possible value in the real world, it is not in the data, so I want the dropdown values to only include Woman and Child. When I run the below minimum working example, I recieve this error:

Warning: Error in : `x` must be 'data.frame', not 'environment'.
  47: hypothesize_fn
  46: predicate
  44: check_type
  43: calculate
  41: observe
  40: server [#2]
   3: runApp
   2: print.shiny.appobj
   1: <Anonymous>
Error : `x` must be 'data.frame', not 'environment'.

This error persists on three different machines (one Windows, Mac, and Linux), as well as when I deploy to shinyapps.io (it is present in the logs). I’ve also run the example code found here and here, and get errors, although different ones. It has worked before, but it started breaking a couple nights ago, and reverting back to a previously working version doesn’t fix it.

The reason I cant just pass sort(unique(data$cat1)) into the selectInput() directly is because in my full working project, ui.R and server.R are two different files, and the data is only loaded into server.R. Thanks, all.

Minimum working example

library(bslib)
library(shiny)
library(tidyverse)

data <- tibble("cat1" = c("Woman", "Woman", "Child"), "cat2" = c("b", "c", "c"))

ui <- page_navbar(
  sidebar = sidebar(
    selectInput(
      "filter_category",
      "Categories:",
      choices = NULL,
      selected = NULL,
      multiple = TRUE
    )
  )
)

server <- function(input, output, session) {
  observe({
    updateSelectInput(
      session,
      "filter_letter", 
      choices = sort(unique(data$cat1)),
      selected = sort(unique(data$cat1))
    )
  })
}

shinyApp(ui = ui, server = server)

Possibly related question here, but it hasn’t helped so far.

I have tried:

• Reverting to a previously-functional version. The error persists now.
• Removing the observe() function and returning to static selectInput choices (this works but itsn’t the functionality I want).
• Switching between a Mac, Windows, and Linux machine.
• Deploying to shinyapps.io and using whatever environment they use there.
• Manually setting choices and selected with static vectors inside of the updateSelectInput function.

I was expecting:

A dropdown selectInput in my UI and only contains the levels of the cat1 categorical variable that are present in the data.