calling makeReactiveBinding on an object that already has a binding stops reactivity

[vnijs]

@jcheng5 FYI I was seeing some strange effects in my app using makeReactiveBinding where the data would stop being reactive at some point. Couldn't consistently reproduce. Then I added checks around all calls to makeReactiveBinding so the binding won't be 'created' if a binding already exists and the problem seemed to go away.

Below in screenshot and code to illustrate the issue. The code below runs in Report > R in radiant.data. Sorry, haven't had time to make an easier to reproduce example.

options(width = 100)

## diamonds is reactive
bindingIsActive(as.symbol("diamonds"), env = r_data)

## making sure we don't have extra variables
diamonds <- select(diamonds, price:z)

## add a variable
diamonds <- mutate(diamonds, extra1 = 42)

## column name is added and .get_data() reactive is updated
colnames(diamonds)
colnames(.get_data())

## recreate the binding
makeReactiveBinding("diamonds", env = r_data)

## add another variable
diamonds <- mutate(diamonds, extra2 = 42)

## diamonds is still listed as reactive but ...
bindingIsActive(as.symbol("diamonds"), env = r_data)

## column name is added BUT .get_data() reactive NOT updated
colnames(diamonds)
colnames(.get_data())

[vnijs]

Current work-around:

MRB <- function(x, env = parent.frame(), init = FALSE) {
  if (exists(x, envir = env)) {
    ## if the object exists and has a binding, don't do anything
    if (!bindingIsActive(as.symbol(x), env = env)) {
      shiny::makeReactiveBinding(x, env = env)
    }
  } else if (init) {
    ## initialize a binding (and value) if object doesn't exist yet
    shiny::makeReactiveBinding(x, env = env)
  }
}