updateAceEditor causes out of memory error on chrome

[stewerner]

I'm currently trying to use aceEditor() to display a log file (which is continuously updated). For this I set readOnly = TRUE.

However, despite the fact that (as intended) I can't undo (CTRL + Z) the changes caused by updateAceEditor the undo stack is updated for each modification of the displayed text, which finally leads to chrome's out of memory error:

Here is an example to reproduce this behaviour (exaggerated updating rate):

library(shiny)
library(shinyAce)

ui <- fluidPage(
  aceEditor(
    outputId = "myeditor",
    height = "82vh",
    value = "",
    mode = "text",
    readOnly = TRUE
  )
)

server <- function(input, output, session) {
  log <- reactiveVal()
  observe({
    invalidateLater(300)
    log(c(isolate(log()), paste(Sys.time(), "- This is going to pile-up in the ace.js undo stack, despite using readOnly = TRUE")))
  })
  observeEvent(log(), {
    updateAceEditor(session, "myeditor", value = paste0(log(), collapse = "\n"))
  })
}

shinyApp(ui, server)

I think it would be useful to disable the undo stack when readOnly = TRUE or updateAceEditor is used. Another option would be to provide a function to reset the undo stack.

Edit: introducing the editor option mergeUndoDeltas: true | false | 'always'; could be another approach.

[vnijs]

That makes sense. I'd be happy to review a PR.