Fix more warnings when running old Bundler with latest RubyGems

Also fix platform warnings when Bundler's entrypoint is bundler's
binstub.

Author: deivid-rodriguez

.github/workflows/install-rubygems.yml

@@ -87,6 +87,8 @@ jobs:
         run: |
           BUNDLER_VERSION=2.6.9 ruby -rbundler/setup -e1 2> errors.txt || (cat errors.txt && exit 1)
           test ! -s errors.txt || (cat errors.txt && exit 1)
+          bundle _2.6.9_ -v 2> errors.txt || (cat errors.txt && exit 1)
+          test ! -s errors.txt || (cat errors.txt && exit 1)
       - name: Build bundler
         run: gem build bundler.gemspec
         working-directory: ./bundler

lib/rubygems.rb

@@ -249,6 +249,16 @@ def self.bin_path(name, exec_name = nil, *requirements)
     find_spec_for_exe(name, exec_name, requirements).bin_file exec_name
   end
 
+  def self.find_and_activate_spec_for_exe(name, exec_name, requirements)
+    spec = find_spec_for_exe name, exec_name, requirements
+    Gem::LOADED_SPECS_MUTEX.synchronize do
+      spec.activate
+      finish_resolve
+    end
+    spec
+  end
+  private_class_method :find_and_activate_spec_for_exe
+
   def self.find_spec_for_exe(name, exec_name, requirements)
     raise ArgumentError, "you must supply exec_name" unless exec_name
 
@@ -273,6 +283,35 @@ def self.find_spec_for_exe(name, exec_name, requirements)
   end
   private_class_method :find_spec_for_exe
 
+  ##
+  # Find and load the full path to the executable for gem +name+.  If the
+  # +exec_name+ is not given, an exception will be raised, otherwise the
+  # specified executable's path is returned.  +requirements+ allows
+  # you to specify specific gem versions.
+  #
+  # A side effect of this method is that it will activate the gem that
+  # contains the executable.
+  #
+  # This method should *only* be used in bin stub files.
+
+  def self.activate_and_load_bin_path(name, exec_name = nil, *requirements)
+    spec = find_and_activate_spec_for_exe name, exec_name, requirements
+
+    if spec.name == "bundler"
+      # Make sure there's no version of Bundler in `$LOAD_PATH` that's different
+      # from the version we just activated. If that was the case (it happens
+      # when testing Bundler from ruby/ruby), we would load Bundler extensions
+      # to RubyGems from the copy in `$LOAD_PATH` but then load the binstub from
+      # an installed copy, causing those copies to be mixed and yet more
+      # redefinition warnings.
+      #
+      require_path = $LOAD_PATH.resolve_feature_path("bundler").last.delete_suffix("/bundler.rb")
+      Gem.load_bundler_extensions(spec.version) if spec.full_require_paths.include?(require_path)
+    end
+
+    load spec.bin_file(exec_name)
+  end
+
   ##
   # Find the full path to the executable for gem +name+.  If the +exec_name+
   # is not given, an exception will be raised, otherwise the
@@ -285,12 +324,7 @@ def self.find_spec_for_exe(name, exec_name, requirements)
   # This method should *only* be used in bin stub files.
 
   def self.activate_bin_path(name, exec_name = nil, *requirements) # :nodoc:
-    spec = find_spec_for_exe name, exec_name, requirements
-    Gem::LOADED_SPECS_MUTEX.synchronize do
-      spec.activate
-      finish_resolve
-    end
-    spec.bin_file exec_name
+    find_and_activate_spec_for_exe(name, exec_name, requirements).bin_file exec_name
   end
 
   ##

lib/rubygems/installer.rb

@@ -228,6 +228,7 @@ def check_executable_overwrite(filename) # :nodoc:
       ruby_executable = true
       existing = io.read.slice(/
           ^\s*(
+            Gem\.activate_and_load_bin_path\( |
             load \s Gem\.activate_bin_path\(
           )
           (['"])(.*?)(\2),
@@ -769,7 +770,11 @@ def app_script_text(bin_file_name)
         end
       end
 
-      load Gem.activate_bin_path('#{spec.name}', '#{bin_file_name}', version)
+      if Gem.respond_to?(:activate_and_load_bin_path)
+        Gem.activate_and_load_bin_path('#{spec.name}', '#{bin_file_name}', version)
+      else
+        load Gem.activate_bin_path('#{spec.name}', '#{bin_file_name}', version)
+      end
     TEXT
   end
 

test/rubygems/test_gem_installer.rb

@@ -48,7 +48,11 @@ def test_app_script_text
           end
         end
 
-        load Gem.activate_bin_path('a', 'executable', version)
+        if Gem.respond_to?(:activate_and_load_bin_path)
+          Gem.activate_and_load_bin_path('a', 'executable', version)
+        else
+          load Gem.activate_bin_path('a', 'executable', version)
+        end
       EOF
 
       wrapper = installer.app_script_text "executable"