Can shinyoutput entries be removed?

[mmuurr]

Can we remove elements from a shinyoutput object?
Some simple testing suggests no (at least not with the first few obvious guesses):

## in shinyServer(function(input, output, session)):

output$foo <- renderText("foo")

## rm(output[["foo"]]) ## doesn't work
## output[["foo"]] <- NULL ## also doesn't work

The reason for wanting such a function is to prevent server-side memory accumulation in long-running applications that frequently call insertUI() & removeUI().

For example, insertUI() might insert a dynamically-generated textOutput("foo", ...) element coupled to a corresponding output[["foo"]] <- renderText(...) assignment to the session's output object. Later, when removeUI() removes the textOutput("foo", ...) element, I'd like to 'clean-up' the session's output object by removing the output[["foo"]] entry. (In this example, "foo" is a randomly-generated unique ID.)

For applications where this is a frequent procedure the UI-side of the application can be kept tidy, but I suspect the server-side output object simply continues to accumulate these entries.

Is there any way to remove a specific entry in the output object by that entry's ID?
(I can't find any such function/procedure in the docs.)

[jcheng5]

Note: "doesn't work" means

Error in .subset2(x, "impl")$defineOutput(name, value, label) : 
  Unexpected NULL output for plot