I would like to create a simple shiny app to let the user export a yaml file. Creating the structure of a yaml file can be tricky. When I want to use the selectInput to give the user multiple options it works when we only have that function. Here is some reproducible example:

library(shiny)
library(yaml)

ui <- fluidPage(
  selectInput("Letters", "Select a letter:", LETTERS[1:4]),
  downloadButton("export_yaml", "Export yaml")
)

server <- function(input, output) {
  data <- reactive({
    list(test_yaml = setNames(list(TRUE), input$Letters))
  })
  
  output$export_yaml <- downloadHandler(
    filename = function() {
      paste0('test_yaml', ".yaml")
    },
    content = function(file) {
      yaml_input <- as.yaml(data())
      cat(as.character(yaml_input), sep = "n", file = file, append = TRUE)
    }
  )
}

shinyApp(ui, server)

Output test_yaml.yaml:

test_yaml:
  A: yes

This is right, but when we add another option above the current function it returns an empty string as named value for the option. Here is the code:

library(shiny)
library(yaml)

ui <- fluidPage(
  selectInput("Letters", "Select a letter:", LETTERS[1:4]),
  downloadButton("export_yaml", "Export yaml")
)

server <- function(input, output) {
  data <- reactive({
    list(test_yaml = list(test = TRUE), # Changed code
         setNames(list(TRUE), input$Letters))
  })
  
  output$export_yaml <- downloadHandler(
    filename = function() {
      paste0('test_yaml', ".yaml")
    },
    content = function(file) {
      yaml_input <- as.yaml(data())
      cat(as.character(yaml_input), sep = "n", file = file, append = TRUE)
    }
  )
}

shinyApp(ui, server)

Output test_yaml.yaml:

test_yaml:
  test: yes
'':
  A: yes

This is not my expected output, It should be like this:

test_yaml:
  test: yes
  A: yes

Since we just give another input option and not a new nested name. So I was wondering how we could create such yaml structure?