Sorting a named list using actionButton Shiny

I have a named list as follows:

vegshop <- list(
    "FRUITS" = c("MANGO", "JACKFRUIT", "BANANA"),
    'VEGETABLES' = c("OKRA", "BEANS", "CABBAGE")
)

I am trying to order the list based on the names, and this works fine.

vegshop[order(names(vegshop), decreasing = F)]

However when I try to do using an actionButton(), I am getting the following error:

the condition has `length > 1` and only the first element will be used

or

Warning: Error in order: unimplemented type 'list' in 'orderVector1'

A workable example is as follows:

vegshop <- list(
    "FRUITS" = c("MANGO", "JACKFRUIT", "BANANA"),
    'VEGETABLES' = c("OKRA", "BEANS", "CABBAGE")
)
grocer <- list(
    "GROCERY" = c("CEREALS", "PULSES", "TOILETRIES"),
    "CLEANERS" = c("DETERGENTS", "FLOOR CLEANERS", "WIPES")
)

library(shiny)

ui <- shinyUI(
    fluidPage(
    actionButton(style = "font-size: 10px;",inputId = "a2z", label = "Sort-A-Z", icon = icon("sort-alpha-asc")),
    radioButtons(inputId = "shopsel", label = "SELECT SHOP", choices = c("SHOPS","SUPERMARKETS"), selected = "SHOPS", inline = TRUE),
    uiOutput("shoplist")))

server <- function(session,input, output) {
    output$shoplist <- renderUI({
        if(input$shopsel == "SHOPS") {
         selectInput(inputId = "vegShopList", label = "SHOPLIST", choices = vegshop, selected = c('MANGO', 'JACKFRUIT', 'BANANA'), multiple = TRUE, selectize = FALSE)   
        } else if(input$shopsel == "SUPERMARKETS") {
        selectInput(inputId = "smList", label = "SUPERMARKET", choices = grocer, selected = c('CEREALS', 'PULSES', 'TOILETRIES'), multiple = TRUE, selectize = FALSE)    
        }
    })

    observeEvent(input$a2z, {
        if(input$shopsel == "SHOPS") {
            updateSelectInput(session, inputId = "vegShopList", choices = vegshop[order(vegshop), decreasing = F], selected = NULL)
        } else if(input$shopsel == "SUPERMARKETS") {
            updateSelectInput(session, inputId = "smList", choices = grocer[order(grocer), decreasing = F], selected = NULL)
        }
        })
}

shinyApp(ui = ui, server = server)

How could I get the list sorted by the names using the actionButton().