PickerInput subcategories with only one element

Question

I've been trying to make a pickerInput from package ShinyWidgets with subcategories.

library(shiny)
library(shinyWidgets)

ui <- fluidPage(
  tags$h2("Select / Deselect all"),
  pickerInput(
    inputId = "p1",
    label = "Select all option",
    choices = list(subA = c("a","b","c"),
                   subB = c("a"),
                   subC = c("a","b")),
    multiple = TRUE,
    options = list(`actions-box` = TRUE)
  ),
  verbatimTextOutput("r1")
)

server <- function(input, output, session) {
  output$r1 <- renderPrint(input$p1)
}

shinyApp(ui = ui, server = server)

The problem is when one subcategory has only one element, the output is a bit weird and does not show as the same as the other subcategories. In my example, I can choose the name of the subcategory (subB) but not the element of this one ("a")

Is there a way to fix this?

Answer 1

Make it a list as

    choices = list(subA = list("a","b","c"),
                   subB = list("a"),
                   subC = list("a","b"))