make finalize() a no-op for never-constructed module objects

An object created without arguments for a class without a default
constructor holds the dummy pointer, which is an environment rather
than an external pointer. Its finalize() method passed it to
CppObject__finalize, which failed, and the failure surfaced as
"Expecting an external pointer: [type=environment]" during garbage
collection.

Author: kevinushey

ChangeLog

@@ -1,3 +1,11 @@
+2026-10-22  Kevin Ushey  <kevinushey@gmail.com>
+
+	* R/Module.R (cpp_refMethods): Make finalize() a no-op for a module
+	object that was never constructed (created without arguments for a class
+	without a default constructor); it used to fail on the dummy pointer, and
+	the failure surfaced as an error message at garbage collection
+	* inst/tinytest/test_module.R: Add test
+
 2026-10-22  Michael Sumner <mdsumner@gmail.com>
 
 	* R/00_classes.R: Define C++Field, C++OverloadedMethods and C++Constructor

R/Module.R

@@ -400,14 +400,18 @@ method_wrapper <- function( METHOD, where ){
 ## create a named list of the R methods to invoke C++ methods
 ## from the C++ class with pointer xp
 cpp_refMethods <- function(CLASS, where) {
+    # an object created without arguments for a class lacking a default
+    # constructor holds the dummy pointer (see cpp_object_dummy), which is
+    # not an external pointer: there is nothing to finalize for it
     finalizer <- eval( substitute(
             function(){
-                .Call( CppObject__finalize, class_pointer , .pointer )
+                if( ! identical( .pointer, dummy ) )
+                    .Call( CppObject__finalize, class_pointer , .pointer )
             },
             list(
-                CLASS = CLASS@pointer,
                 CppObject__finalize = CppObject__finalize,
-                class_pointer = CLASS@pointer
+                class_pointer = CLASS@pointer,
+                dummy = .dummyInstancePointer
             )
         ) )
         mets <- c(

inst/tinytest/test_module.R

@@ -123,3 +123,10 @@ gctorture(TRUE)
 res <- gadget$value()
 gctorture(FALSE)
 expect_identical( res, c(1, 2, 3) )
+
+#    test.Module.finalize.dummy <- function(){
+## an object created without arguments for a class lacking a default
+## constructor holds the dummy pointer; finalizing it must be a no-op
+## rather than an error (which used to surface at garbage collection)
+r <- new( ModuleRandomizer )
+expect_identical( r$finalize(), NULL )