R devel - Aug 2020 - utils::isS3stdGeneric chokes on primitives and identity

Dear R-devel,

utils::isS3stdGeneric tries to subset the body of the function it's fed,
primitives don't like that because they don't have a body, identity
doesn't
like it either because it's body is a symbol.

According to the doc, any function is a legal input.

See below:

identity
#> function (x)
#> x
#> <bytecode: 0x0000000013d6da28>
#> <environment: namespace:base>

max
#> function (..., na.rm = FALSE)  .Primitive("max")

isS3stdGeneric(identity)
#> Error in bdexpr[[1L]]: objet de type 'symbol' non indi?able

isS3stdGeneric(max)
#> Error in while (as.character(bdexpr[[1L]]) == "{") bdexpr <-
bdexpr[[2L]]: l'argument est de longueur nulle

Here is a simple fix :

isS3stdGeneric <- function(f) {
  {
    bdexpr <- body(f)
    if(is.null(bdexpr) || !is.call(bdexpr)) return(FALSE)
    while (as.character(bdexpr[[1L]]) == "{") bdexpr <-
bdexpr[[2L]]
    ret <- is.call(bdexpr) && identical(bdexpr[[1L]],
as.name("UseMethod"))
    if (ret)
      names(ret) <- bdexpr[[2L]]
    ret
  }
}

isS3stdGeneric(identity)
#> [1] FALSE
isS3stdGeneric(max)
#> [1] FALSE

Best,

Antoine

	[[alternative HTML version deleted]]

I added that so I can look at the proposed fix and put it or something
similar in bugzilla for review final review.

Apologies for the oversight.

~G

On Wed, Aug 19, 2020 at 3:40 PM Antoine Fabri <antoine.fabri at gmail.com>
wrote:
> Dear R-devel,
>
> utils::isS3stdGeneric tries to subset the body of the function it's
fed,
> primitives don't like that because they don't have a body, identity
doesn't
> like it either because it's body is a symbol.
>
> According to the doc, any function is a legal input.
>
> See below:
>
> identity
> #> function (x)
> #> x
> #> <bytecode: 0x0000000013d6da28>
> #> <environment: namespace:base>
>
> max
> #> function (..., na.rm = FALSE)  .Primitive("max")
>
> isS3stdGeneric(identity)
> #> Error in bdexpr[[1L]]: objet de type 'symbol' non indi?able
>
> isS3stdGeneric(max)
> #> Error in while (as.character(bdexpr[[1L]]) == "{") bdexpr
<-
> bdexpr[[2L]]: l'argument est de longueur nulle
>
> Here is a simple fix :
>
> isS3stdGeneric <- function(f) {
>   {
>     bdexpr <- body(f)
>     if(is.null(bdexpr) || !is.call(bdexpr)) return(FALSE)
>     while (as.character(bdexpr[[1L]]) == "{") bdexpr <-
bdexpr[[2L]]
>     ret <- is.call(bdexpr) && identical(bdexpr[[1L]], as.name
> ("UseMethod"))
>     if (ret)
>       names(ret) <- bdexpr[[2L]]
>     ret
>   }
> }
>
> isS3stdGeneric(identity)
> #> [1] FALSE
> isS3stdGeneric(max)
> #> [1] FALSE
>
> Best,
>
> Antoine
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
	[[alternative HTML version deleted]]

>>>>> Gabriel Becker writes:
> I added that so I can look at the proposed fix and put it or something
> similar in bugzilla for review final review.
> Apologies for the oversight.
Fixed now with

-    while(as.character(bdexpr[[1L]]) == "{")
+    while(is.call(bdexpr) && (as.character(bdexpr[[1L]]) ==
"{"))

(the suggested fix does not work on things like
foo <- function(x) {{ x }} 
...)

Best
-k
> ~G
> On Wed, Aug 19, 2020 at 3:40 PM Antoine Fabri <antoine.fabri at
gmail.com>
> wrote:
>> Dear R-devel,
>> 
>> utils::isS3stdGeneric tries to subset the body of the function it's
fed,
>> primitives don't like that because they don't have a body,
identity doesn't
>> like it either because it's body is a symbol.
>> 
>> According to the doc, any function is a legal input.
>> 
>> See below:
>> 
>> identity
>> #> function (x)
>> #> x
>> #> <bytecode: 0x0000000013d6da28>
>> #> <environment: namespace:base>
>> 
>> max
>> #> function (..., na.rm = FALSE)  .Primitive("max")
>> 
>> isS3stdGeneric(identity)
>> #> Error in bdexpr[[1L]]: objet de type 'symbol' non
indi?able
>> 
>> isS3stdGeneric(max)
>> #> Error in while (as.character(bdexpr[[1L]]) == "{")
bdexpr <-
>> bdexpr[[2L]]: l'argument est de longueur nulle
>> 
>> Here is a simple fix :
>> 
>> isS3stdGeneric <- function(f) {
>> {
>> bdexpr <- body(f)
>> if(is.null(bdexpr) || !is.call(bdexpr)) return(FALSE)
>> while (as.character(bdexpr[[1L]]) == "{") bdexpr <-
bdexpr[[2L]]
>> ret <- is.call(bdexpr) && identical(bdexpr[[1L]], as.name
>> ("UseMethod"))
>> if (ret)
>> names(ret) <- bdexpr[[2L]]
>> ret
>> }
>> }
>> 
>> isS3stdGeneric(identity)
>> #> [1] FALSE
>> isS3stdGeneric(max)
>> #> [1] FALSE
>> 
>> Best,
>> 
>> Antoine
>> 
>> [[alternative HTML version deleted]]
>> 
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>> 
> 	[[alternative HTML version deleted]]
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel