no longer use require() in low-level code needing namespace

git-svn-id: https://svn.r-project.org/R/trunk@87247 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: maechler

doc/NEWS.Rd

@@ -103,6 +103,13 @@
       convert row names used for indexing using \code{I()}, which will
       lead to faster execution in cases where \code{sort = TRUE} and
       \code{all.x} and/or \code{all.y} are set to \code{TRUE}.
+
+      \item \pkg{methods} package internal \code{.requirePackage()} now
+      calls \code{requireNamespace(p)} instead of \code{require(p)}, hence
+      no longer adding packages to the \code{search()} path in cases
+      methods or class definitions are needed.  Consequently, previous
+      workflows relying on the old behaviour will have to be amended by
+      adding corresponding \code{library(p)} calls.
     }
   }
 

src/library/methods/R/RClassUtils.R

@@ -1807,46 +1807,41 @@ substituteFunctionArgs <-
 
 ## bootstrap version:  all classes and methods must be in the version of the methods
 ## package being built in the toplevel environment: MUST avoid require("methods") !
-.requirePackage <- function(package, mustFind = TRUE)
+.requirePackage <- function(package, mustFind = TRUE, quietly = FALSE)
     topenv(parent.frame())
 
 ## real version of .requirePackage
-..requirePackage <- function(package, mustFind = TRUE) {
-    value <- package
+..requirePackage <- function(package, mustFind = TRUE, quietly = FALSE) {
     if(nzchar(package)) {
         ## lookup as lightning fast as possible:
-	if (.Internal(exists(package, .Internal(getNamespaceRegistry()),
-			     "any", FALSE)))
-            value <- getNamespace(package)
+        if(!is.null(ns <-.Internal(getRegisteredNamespace(package))))
+           return(ns)
         else {
             if(identical(package, ".GlobalEnv"))
                 return(.GlobalEnv)
             if(identical(package, "methods"))
                 return(topenv(parent.frame())) # booting methods
+            ## else continue
         }
     }
-    if(is.environment(value))
-        return(value)
-    topEnv <- getOption("topLevelEnvironment")
-    if(is.null(topEnv))
-        topEnv <- .GlobalEnv
+    topEnv <- getOption("topLevelEnvironment", default = .GlobalEnv)
     if(!is.null(pkgN <- get0(".packageName", topEnv, inherits=TRUE)) &&
        .identC(package, pkgN))
         return(topEnv) # kludge for source'ing package code
+
     ## If called from .findInheritedMethods which disables S4 primitive dispatch,
     ## allow it here, as namespace loading hooks may need it:
     if(!.allowPrimitiveMethods(TRUE))
         on.exit(.allowPrimitiveMethods(FALSE))
-    if(nzchar(package) && require(package, character.only = TRUE)) {}
+    if(nzchar(package) && requireNamespace(package, quietly=quietly))
+        getNamespace(package)
     else {
         if(mustFind)
           stop(gettextf("unable to load required package %s",
                         sQuote(package)),
                domain = NA)
-        else
-          return(NULL)
     }
-    getNamespace(package)
+    ## else return(NULL)
 }
 
 .classDefEnv <- function(classDef) {