validObject throws non-caught error when slot doesn't exist

I have been retooling an S4 class definition to include another slot 
and have found that the methods::validObject function (defined in 
methods/R/SClasses.R) in R-devel throws an error that isn't caught 
internally (and thus not controllable by 'test' argument) when 
retrieving a non-existent slot. The offending line of code is shown 
below:

validObject

function (object, test = FALSE, complete = FALSE)
{
...
   for (i in seq_along(slotTypes)) {
       classi <- slotTypes[[i]]
       sloti <- slot(object, slotNames[[i]]) # offending line of code

One potential patch is to substitute the offending line with

       sloti <- try(slot(object, slotNames[[i]]), silent = TRUE)
       if (class(sloti) == "try-error") {
           errors <- c(errors, paste("missing slot \"", slotNames[[i]],
               "\"", sep = ""))
           next
       }

Here is a reproduce and an example using vaildObject2 that substitutes 
the offending line with the code given above:

setClass("Foo", representation(bar = "character"))

[1] "Foo"

a <- new("Foo", bar = letters)
setClass("Foo", representation(bar = "character", star = "numeric"))

[1] "Foo"

validObject(a, test = TRUE)

Error in slot(object, slotNames[[i]]) :
 no slot of name "star" for this object of class "Foo"

validObject2(a, test = TRUE)

[1] "missing slot \"star\""

sessionInfo()

R version 2.10.0 Under development (unstable) (2009-06-12 r48755)
i386-apple-darwin9.6.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base    


Patrick

Patrick,

Thanks for the bug report and the proposed patch.

There are some related ways that validObject can fail (e.g., if the 
revised class definition extends one of the object types or if the 
object is an S3 object), so the patch needs to be a little more 
general, but I will commit something to the 2.10 development version 
and send mail).

John

Patrick Aboyoun wrote:

I have been retooling an S4 class definition to include another slot 
and have found that the methods::validObject function (defined in 
methods/R/SClasses.R) in R-devel throws an error that isn't caught 
internally (and thus not controllable by 'test' argument) when 
retrieving a non-existent slot. The offending line of code is shown 
below:

validObject

function (object, test = FALSE, complete = FALSE)
{
...
   for (i in seq_along(slotTypes)) {
       classi <- slotTypes[[i]]
       sloti <- slot(object, slotNames[[i]]) # offending line of code

One potential patch is to substitute the offending line with

       sloti <- try(slot(object, slotNames[[i]]), silent = TRUE)
       if (class(sloti) == "try-error") {
           errors <- c(errors, paste("missing slot \"", slotNames[[i]],
               "\"", sep = ""))
           next
       }

Here is a reproduce and an example using vaildObject2 that 
substitutes the offending line with the code given above:

setClass("Foo", representation(bar = "character"))

[1] "Foo"

a <- new("Foo", bar = letters)
setClass("Foo", representation(bar = "character", star = "numeric"))

[1] "Foo"

validObject(a, test = TRUE)

Error in slot(object, slotNames[[i]]) :
 no slot of name "star" for this object of class "Foo"

validObject2(a, test = TRUE)

[1] "missing slot \"star\""

sessionInfo()

R version 2.10.0 Under development (unstable) (2009-06-12 r48755)
i386-apple-darwin9.6.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base   

Patrick