R Shiny Datatable: Prevent already selected row from being deselected when it is clicked again

R (Version 3.4.1) I'm using the DT (Version 0.4) package in DT (Version 1.0.5) and need to prevent already selected rows from being deselected when the user clicks again. For example, in the image below, if the user clicks on row 3 again, the row should not be deselected. However, if the user selects a new row, that new row will be selected and the previous row will be deselected.

I think what I need is for the datatable to completely ignore click events on selected rows.

I tried using shinyjs::onclickthe method shown below, but it's not ideal, as it seems to "deselect and reselect" the selected row (the blue highlight disappears and reappears when clicked again), rather than preventing deselect .

library(shiny)
library(DT)
library(shinyjs)

shinyApp(
  ui <- shinyUI(
    fluidPage(
      shinyjs::useShinyjs(),
      DTOutput("test")
    )
  ),  
  server <- shinyServer(function(input, output, session) {

    output$test <- renderDT({
      datatable(head(iris), selection = 'single')
    })    
    shinyjs::onclick("test",
               selectRows(dataTableProxy("test"), selected = input$test_rows_selected)
             )    
  })
)

I wonder if there is an easy way to do this. Thanks!