[Rd] Class not found when search in .onLoad

From: Renaud Gaujoux <renaud_at_mancala.cbio.uct.ac.za>
Date: Thu, 23 Jun 2011 13:22:06 +0200


Hi,

I am facing with a strange behaviour of isClass and extends when these are called in .onLoad in both R 2.12.1 and R 2.13.0. This is preventing my package from doing some object initializations at a proper place (i.e. in .onLoad).

Suppose one defines two S4 classes in a package, and that one needs to check the inheritance between these two when loading the package (e.g. to validate slots in objects).
See package attached or code below (not sure attachments can go through).

in R 2.13.0:
At the loading check after installation, the classes are not found by `isClass` and `extends` when these are called in .onLoad, but are correctly found when called in .onAttach. However findClass correctly finds the class in both case, as well as isClass if it is called with the argument `where=asNamespace('<THE.PACKAGE.NAME>')`. When the package is loaded from an open R session, the behaviour is the same.

in R 2.12.1:
the classes are correctly found by isClass and extends when these are called in .onLoad or .onAttach, but only at installation (i.e. at the loading check after R CMD INSTALL).
When the package is loaded from an open R session, one fails to find the classes only in .onLoad while in .onAttach they are correctly found.

This is really an issue as up to now I was using .onAttach to do my checks and initialization, but it is not a wise thing as package that would only need to import my package (load and not attach) will not get internal objects properly initialized. All this should be done in .onLoad, but I cannot do it due to this behaviour of `extends`.

Can someone provide some explanations or work around.

Thank you,
Renaud

############

# script.R
############

setClass('A', representation(data='numeric'))

setClass('B', contain='A')

check.classes <- function(){

a <- new('A')
b <- new('B')

message("isClass('A'): ", methods::isClass('A')) message("isClass('A') in namespace: ", methods::isClass('A', where=asNamespace('anRpackage')))
message("findClass('A'): ")
print(methods::findClass('A'))

message("isClass('B'): ", methods::isClass('B')) message("isClass('B') in namespace: ", methods::isClass('B', where=asNamespace('anRpackage')))
message("findClass('B'): ")
print(methods::findClass('B'))

message("extends('B', 'A'): ", methods::extends('B', 'A'))
message("is(a, 'A'): ", is(a, 'A'))
message("inherits(a, 'A'): ", inherits(a, 'A'))
message("is(b, 'A'): ", is(b, 'A'))

}

.onLoad <- function(libname, pkgname=NULL){ cat("\n## .onLoad ##\n")
check.classes()
}

.onAttach <- function(libname, pkgname){ cat("\n## .onAttach ##\n")
check.classes()
}
############

################################################
################################################

# Output

################################################
################################################

################################################
# R-2.13.0 CMD INSTALL anRpackage_1.0.tar.gz
################################################
* installing *source* package ‘anRpackage’ ... ** R ** preparing package for lazy loading ** help *** installing help indices

** building package indices ...
** testing if installed package can be loaded

## .onLoad ##

isClass('A'): FALSE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): FALSE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): FALSE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE

## .onAttach ##

isClass('A'): TRUE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): TRUE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): TRUE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE

################################################
# From a R-2.12.1 Console
################################################

## .onLoad ##

isClass('A'): FALSE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): FALSE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): FALSE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE

## .onAttach ##

isClass('A'): TRUE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): TRUE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): TRUE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE

################################################
# R-2.12.1 CMD INSTALL anRpackage_1.0.tar.gz
################################################

## .onLoad ##

isClass('A'): TRUE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): TRUE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): TRUE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE

## .onAttach ##

isClass('A'): TRUE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): TRUE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): TRUE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE

################################################
# From a R-2.12.1 Console
################################################

## .onLoad ##

isClass('A'): FALSE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): FALSE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): FALSE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE

## .onAttach ##

isClass('A'): TRUE
isClass('A') in namespace: TRUE
findClass('A'):

[[1]]
<environment: namespace:anRpackage>
isClass('B'): TRUE
isClass('B') in namespace: TRUE
findClass('B'):

[[1]]
<environment: namespace:anRpackage>

extends('B', 'A'): TRUE
is(a, 'A'): TRUE
inherits(a, 'A'): TRUE
is(b, 'A'): TRUE  

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