The UI function cannot use the request argument

[kamilzyla]

Background

When using bookmarking in Shiny, the UI must be a function. According to the documentation of shiny::enableBookmarking() it should take request as an argument, but its contents are not documented and experiments prove that the function can also take no arguments.

Thus both UI definitions below should work in vanilla Shiny:

ui <- function() "Hello!"

ui <- function(request) {
  dput(request)
  "Hello!"
}

We encountered this while working on #283.

Problem

With legacy_entrypoint: source both UI definitions should work as in vanilla Shiny. However if the request argument is actually used in the function (dput(request)) it will not work in Rhino.