[Rd] Recursion error after upgrade to R_2.11.1 [Sec=Unclassified]

[Martin Morgan]

On 10/06/2010 06:12 PM, Troy Robertson wrote:
> Hi all,
> 
> After no replies to my previous message I thought I might show some code to demonstrate the change and again seek any explanation for the error now thrown by my code after upgrading from 2.10.1 to 2.11.1.
> 
> Thanks
> Troy
> --------------------------------------------------------
> setClass("PortableObject",
>         representation(test1    = "character"),
> 
>         prototype(      test1   = ""),
>           contains = ".environment"
> )
> 
> setMethod("initialize", "PortableObject",
>     function(.Object, ..., .xData=new.env(parent=emptyenv())) {
>                 .Object <- callNextMethod(.Object, ..., .xData=.xData)
> 
>                 .Object at test1 <- "Foo"
>                 # Following line works under 2.10.1 but now throws
>                 # Error: evaluation nested too deeply: infinite recursion / options(expressions=)?
>                 #####.Object[["test2"]] <- "Bar"
>                 # The following does what I want though
>                 .Object$test3 <- "Baa"
> 
>                 return(.Object)
>         }
> )
> 
> e <- new("PortableObject")

The explicit example does help -- it's clear what bug you are
encountering. Here's the code in R-2.10

> selectMethod("[[<-", ".environment")
Method Definition:

function (x, i, j, ..., value)
{
    call <- sys.call()
    call[[2]] <- x at .Data
    eval.parent(call)
    x
}


and 2.11.1

> selectMethod("[[<-", ".environment")
Method Definition:

function (x, i, j, ..., value)
{
    .local <- function (x, i, j, ..., exact = TRUE, value)
    {
        call <- sys.call()
        call[[2]] <- x at .Data
        eval.parent(call)
        x
    }
    .local(x, i, j, ..., value = value)
}

Apparently the 'exact' argument has been added, and because the method
signature differs from the generic, a .local function is created. That
'sys.call()' originally returned the environment in which the generic
was called, but now it returns the environment in which .local is
defined. And so eval() keeps evaluating .local(). This I think is a bug.

For what it's worth, if I were interested in minimizing copying I would
set up initialize so that it ended with callNextMethod(<...>), on the
hopes that the method eventually called would take care not to make too
many copies on slot assignment.

Martin

> 
> alterEGo <- function(o = "EPOCObject") {
>         o at test1 <- "Boo"
> 
>         # Following line works under 2.10.1 but now throws
>         # Error: evaluation nested too deeply: infinite recursion / options(expressions=)?
>         ####o[["test2"]] <- "Who"
>         # The following does what I want though
>         o$test3 <- "Hoo"
> 
>         # NOTE: No return
> }
> 
> alterEGo(e)
> e at test1
> e$test2
> e[["test3"]]
> e at .xData[["test3"]]
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