Reusing leaflet map elements in custom functions in Shiny/R

Question

I have an application that reuses several leaflet elements, so I'm trying to build functions to streamline my code.

All of my logical attempts failed, so I utilized an example I was familiar with here. I copied the format and created functions for markers and polygons, seen in the example below:

library(leaflet)
library(shiny)


markerFunction <- function(map, x, y){
  addCircleMarkers(
    map, x, y, 
    color = "red"
  )
}

polygonFunction <- function(map, polygon){
  addPolygons(
    map, polygon, 
    color = "red"
  )
}

# shinyapp 
shinyApp(
  # ui
  ui = fixedPage(
    # leaflet output 
    leafletOutput("map", height = 600)
  ),  # END UI

  # server
  server = function(input, output, session){

    # map output 
    output$map <- renderLeaflet({
      leaflet() %>% 
        addTiles
    })  # END RENDER LEAFLET 

    # map proxy
    proxy <- leafletProxy("map")

    # observe
    observe({
      proxy %>% 
        markerFunction(40, 50) %>% 
        polygonFunction(gadmCHE)
    })
  }  # END SERVER 
)

The marker function works fine, but the polygon function spits the error:

Warning: Error in derivePolygons: addPolygons must be called with both lng and lat, or with neither.

which is the error I get when I don't include data = explicitly. When I add data = polygon to the function definition and data = gadmCHE to the polygonFunction() call, I get the error:

Warning: Error in polygonFunction: unused argument (data = gadmCHE)

Running the markerFunction() on its own yields the expected result, but I'm perplexed how it works without including the map argument. When I remove it from the function, it no longer works.

I've tried many configurations and can't get any of them to work except for the markerFunction() as it exists in the above example app. I have tried including and excluding the map argument, explicitly defining other arguments (like x, y, and data) in both the function definition and function calls, excluding the explicit arguments with no luck. I want to create similar functions for polygons as well, but haven't found a solution.

Answer 1

As @TimSalabim pointed out, the following function definition and call work (in their respective places):

polygonFunction <- function(map, polygon){
  addPolygons(
    map, data = polygon, 
    color = "red"
  )
} 


polygonFunction(gadmCHE)