[Rd] Inspect a "delayed" assigned whose value throws an error?

[Hadley Wickham]

If it was any other environment than the global, you could use substitute:

e <- new.env()
delayedAssign("foo", stop("Hey!"), assign.env = e)
substitute(foo, e)

delayedAssign("foo", stop("Hey!"))
substitute(foo)

Hadley

On Mon, Jan 26, 2015 at 12:53 PM, Henrik Bengtsson <hb at biostat.ucsf.edu> wrote:
> Hi, I got an interesting programming challenge:
>
> How do you inspect an object which is assigned via delayedAssign() and
> that throws an error as soon as it is "touched" (=the value is
> evaluated)?  Is it possible?
>
>
> MINIMAL EXAMPLE:
>
> $ R --vanilla
>> delayedAssign("foo", stop("Hey!"))
>
> (If you find this minimal example silly/obvious, please skip down to
> the real example at the end)
>
>> foo
> Error: Hey!
>
>> str(foo)
> Error in str(foo) : Hey!
> In addition: Warning message:
> In str(foo) : restarting interrupted promise evaluation
>
>> mode(foo)
> Error in mode(foo) : Hey!
> In addition: Warning message:
> In mode(foo) : restarting interrupted promise evaluation
>
>> .Internal(inspect(foo))
> Error: Hey!
> In addition: Warning message:
> restarting interrupted promise evaluation
>
>> traceback()
> 1: stop("Hey!")
>
> Is there anyway I can inspect this object using the R API without
> evaluating the value in the delayed assignment?  Is it possible to
> test if this is a delayed assigned or not?
>
>
> BACKGROUND:
> The background to this is where I have a function in the R.oo package
> that scans namespaces for functions with a certain class attribute.
> For this I use is.function() and inherits() to inspect each object.
> An aroma.affymetrix user reported on a problem that boiled down to the
> following:
>
> # source("http://bioconductor.org/biocLite.R"); biocLite("hgu133a.db")
>> library("hgu133a.db")
>> is.function(hgu133aPFAM)
> Error: hgu133aPFAM is defunct. Please use select() if you need access to PFAM
>   or PROSITE accessions.
>> .Internal(inspect(hgu133aPFAM))
>
>> traceback()
> 3: stop(paste(msg, collapse = ""), call. = FALSE, domain = NA)
> 2: .Defunct(msg = msg)
> 1: (function ()
>    {
>        if (grepl("PFAM", x)) {
>            bimapName <- paste0(prefix, "PFAM")
>        }
>        else {
>            bimapName <- paste0(prefix, "PROSITE")
>        }
>        x <- dc[[bimapName]]
>        msg = wmsg(paste0(bimapName, " is defunct. ", "Please use select() if you
>  need access to PFAM or PROSITE accessions. \n"))
>        if (interactive()) {
>            .Defunct(msg = msg)
>        }
>    })()
>
> My immediate solution is to perform those tests using tryCatch(), but
> this is interesting, because this function is such that the error is
> only thrown in interactive() sessions, i.e. the following works:
>
> $ Rscript -e "hgu133a.db::hgu133aPFAM"
> [...]
> NULL
>
> This is probably also why none of my aroma.affymetrix system tests
> caught this.  Without tracing the source code behind, which seems
> quite nested, the above is why I believe the assignment is "delayed";
> traceback() shows a body source code, the object evaluates to
> different things depending on interactive().
>
> /Henrik
>
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