How to debug unexported functions from required packages?

Question

A function, in a package I am using is giving me not so informative errors. I don't know what is going on. This function is called internally by the function I call. Something like this:

myres <- the.func(x)

the.func <-function(x){
    unexported.func(x)
}

How do I debug unexported.func ? Using debug doesn't work:

>debug(unexported.func)
Error in debug(undexported.func) : object 'unexported.func' not found

Update: Currently I do nested debug like the following. But I find it inconvenient:

>debug(the.func) # Initiate debugging for the outer function, so I get unexported.func loaded.
>myres <- the.func(x)
Browse[2]>debug(unexported.func) # Now I can call debug with this. 

Answer 1

You can access an unexported function via the ::: (triple-colon) operator, prefacing it with the package namespace name (i.e. the package name).

Assuming the pkgA contains the unexported function unexported.func(), we would set the debugging flag on unexported.func() using:

debug(pkgA:::unexported.func)

If you don't know which package (hence namespace) to use for a given unexported function, you can always determine this using getAnywhere().