[Rd] function remains loaded in the search space after detaching the package

[Joris Meys]

Indeed, when trying :

> detach('package:gdata',unload=TRUE)
> print(object.size(iris),units='Kb')
[1] 6424

However, when I do :
> unloadNamespace('gdata')
> gc()
         used (Mb) gc trigger (Mb) max used (Mb)
Ncells 380471 10.2     667722 17.9   597831 16.0
Vcells 353363  2.7     905753  7.0   902804  6.9

The function used is still print.object_size from gdata

> print(object.size(iris),units='Kb')
[1] 6424

But it can't be found any more...

> getAnywhere('print.object_size')
A single object matching ‘print.object_size’ was found
It was found in the following places
  registered S3 method for print from namespace utils
  namespace:utils
with value
... (here is indeed the code of the original print.object_size)

This is not some kind of behaviour one would expect. I have no clue
how to solve this, but I believe it's safe to say that there's room
for improvement somewhere to avoid calling a function that's
apparently not in the search space. Any other ideas?

Cheers
Joris

On Fri, Feb 24, 2012 at 1:08 PM, Prof Brian Ripley
<ripley at stats.ox.ac.uk> wrote:
> On 24/02/2012 11:20, Martin Maechler wrote:
>>>>>>>
>>>>>>> Joris Meys<jorismeys at gmail.com>
>>>>>>>     on Fri, 24 Feb 2012 11:24:35 +0100 writes:
>>
>>
>>     >  I ran into some very irritating behaviour I don't
>>     >  understand.  Let me illustrate with the package gdata()
>>     >  and the function print.object_size() :
>>
>>     >>  print(object.size(iris),units='Kb')
>>     >  6.3 Kb
>>     >>  getAnywhere(print.object_size)
>>     >  A single object matching ‘print.object_size’ was found It
>>     >  was found in the following places registered S3 method for
>>     >  print from namespace utils namespace:utils with value ...
>>
>>     >  All is well. So now I load gdata
>>
>>     >>  require(gdata)
>>     >  Loading required package: gdata ...  The following
>>     >  object(s) are masked from ‘package:utils’:
>>
>>     >      object.size
>>
>>     >  OK, this is what I would expect:
>>
>>     >>  print(object.size(iris),units='Kb')
>>     >  [1] 6424
>>     >>  getAnywhere(print.object_size)
>>     >  2 differing objects matching ‘print.object_size’ were
>>     >  found in the following places registered S3 method for
>>     >  print from namespace utils namespace:gdata namespace:utils
>>     >  Use [] to view one of them
>>
>>     >  Now I detach gdata again
>>
>>     >>  detach(package:gdata)
>>
>>     >  But the function print.object_size is still the default
>>     >  for object_size objects!
>>
>>     >>  print(object.size(iris),units='Kb')
>>     >  [1] 6424
>>
>>     >  And it can still be found as well:
>>
>>     >>  getAnywhere(print.object_size)
>>     >  2 differing objects matching ‘print.object_size’ were
>>     >  found in the following places registered S3 method for
>>     >  print from namespace utils namespace:gdata namespace:utils
>>     >  Use [] to view one of them
>>
>>     >  Am I missing something?
>>
>> Yes:  the argument  'unload'   of detach().
>>
>> In general: Now that every package has a namespace,
>> you (and others) should learn the difference between
>> attaching and loading - and hence  detach()ing and unloading
>> a package with its namespace.
>>
>>  ?detach
>>  ?library
>>
>> etc should give a good start.
>
>
> A very good point, but actually there is more to this one.  'gdata'
> registers an S3 method which overwrites the one from utils.  Unloading a
> namespace does not unregister its methods (and registration has no stack, so
> there is no way R knows what was there before).
>
> --
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595



-- 
Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Mathematical Modelling, Statistics and Bio-Informatics

tel : +32 9 264 59 87
Joris.Meys at Ugent.be
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