fix S4 lookup in debugcall() (PR#18143)

git-svn-id: https://svn.r-project.org/R/trunk@86532 00db46b3-68df-0310-9c12-caf00c1e9a41

doc/NEWS.Rd

@@ -108,6 +108,10 @@
 
       \item The internal help server on Windows can again serve requests
       sent in quick succession, fixing a regression in \R 4.4.0.
+
+      \item \code{debugcall(\var{S3Generic}())} now also works when a
+      corresponding S4-generic version is in the \pkg{methods} cache
+      (\PR{18143}).
     }
   }
 }

src/library/utils/R/debugcall.R

@@ -1,7 +1,7 @@
 ##  File src/library/utils/R/debugcall.R
 ##  Part of the R package, https://www.R-project.org
 ##
-##  Copyright (C) 1995-2023 The R Core Team
+##  Copyright (C) 1995-2024 The R Core Team
 ##
 ##  This program is free software; you can redistribute it and/or modify
 ##  it under the terms of the GNU General Public License as published by
@@ -30,7 +30,8 @@
     mcall <- match.call(func, call)
 
     env <- parent.frame(2L)
-    if(!(have.methods && methods::isGeneric(funsym))) { # not S4-generic
+    isS4Generic <- have.methods && methods::isGeneric(funsym, env)
+    if(!isS4Generic) {
         s3ret <- isS3stdGeneric(func)
         if(s3ret) {
             genname <- names(s3ret)

tests/reg-tests-1e.R

@@ -1380,6 +1380,7 @@ stopifnot(exprs = {
 })
 ## the last lost row.names => dim(.) was 0 x 3  instead of  d0's  2 x 3, in R <= 4.4.0
 
+
 ## Scan should not treat "NA" as double/complex when na.strings doesn't
 ## include it (PR#17289)
 (r <- tryCid(scan(text="NA", what=double(), na.strings=character())))
@@ -1388,6 +1389,22 @@ stopifnot(inherits(r, "error"))
 stopifnot(inherits(r, "error"))
 
 
+## PR#18143: debugcall(<S3Generic>()) when an S4-generic version is cached
+stopifnot(exprs = {
+    isGeneric("summary", getNamespace("stats4"))
+    isNamespaceLoaded("stats4")
+    isS3stdGeneric(summary) # cached S4 generic is not visible
+})
+debugcall(summary(factor(1)))
+## failed in R <= 4.4.0 with Error in fdef@signature :
+##   no applicable method for `@` applied to an object of class "function"
+stopifnot(isdebugged(summary.factor))
+undebug(summary.factor)
+stopifnot(!isdebugged(summary.factor))
+unloadNamespace("stats4")
+
+
+
 ## keep at end
 rbind(last =  proc.time() - .pt,
       total = proc.time())