[ESS] distinguish busy from non-busy waiting

[Vitalie Spinu]

>> On Mon, Nov 30 2015 11:38, Andreas Leha wrote:

> Vitalie Spinu <spinuvit using gmail.com> writes:
>>>> On Thu, Nov 26 2015 14:30, Andreas Leha wrote:
>>
>>> So, you are basically suggesting that emacs should look at top for me, right?
>>> That would be possible, I guess.  But still, that might give wrong answers if
>>> R has to wait for I/O a lot, for instance.
>>
>> Maybe this is a feature request for R folks. If R is waiting for promt, it
>> should output a different prompt symbol from when the engine is actually
>> running.
>>

> I am not sure, I understand.  In the 'naked' R console, incomplete input
> seems to produce a '+' prompt, while complete input seems to produce an
> empty prompt.

That's what we are tracking right now - difference between + and >. That's not
enough for what you need.

Both of the following produce same result

## complete:
{
    Sys.sleep(10)
}

## incomplete:
{
    Sys.sleep(10


The current tracking is not even enough for what it was intended for. For
example evaluating the following paragraph will not show as busy:

Sys.sleep(.1)
Sys.sleep(100)

And that's the most annoying side of the current system. I see only one way for
a partial fix - sending a NOOP before every eldoc or completion command to check
for actual status of the sub-process. Not sure how reliably it will work though.

  Vitalie