Fix RubyGems not able to require the right gem:

lib/rubygems.rb

@@ -193,11 +193,12 @@ def self.try_activate(path)
     begin
       spec.activate
     rescue Gem::LoadError => e # this could fail due to gem dep collisions, go lax
-      spec_by_name = Gem::Specification.find_by_name(spec.name)
-      if spec_by_name.nil?
+      spec = Gem::Specification.find_unloaded_by_path(path)
+      spec ||= Gem::Specification.find_by_name(spec.name)
+      if spec.nil?
         raise e
       else
-        spec_by_name.activate
+        spec.activate
       end
     end
 

lib/rubygems/specification.rb

@@ -958,6 +958,15 @@ def self.find_by_path(path)
     specification_record.find_by_path(path)
   end
 
+  ##
+  # Return the best specification that contains the file matching +path+
+  # amongst the specs that are not loaded. This method is different than
+  # +find_inactive_by_path+ as it will filter out loaded specs by their name.
+
+  def self.find_unloaded_by_path(path)
+    specification_record.find_unloaded_by_path(path)
+  end
+
   ##
   # Return the best specification that contains the file matching +path+
   # amongst the specs that are not activated.

lib/rubygems/specification_record.rb

@@ -154,6 +154,19 @@ def find_by_path(path)
       spec.to_spec
     end
 
+    ##
+    # Return the best specification that contains the file matching +path+
+    # amongst the specs that are not loaded. This method is different than
+    # +find_inactive_by_path+ as it will filter out loaded specs by their name.
+
+    def find_unloaded_by_path(path)
+      stub = stubs.find do |s|
+        next if Gem.loaded_specs[s.name]
+        s.contains_requirable_file? path
+      end
+      stub&.to_spec
+    end
+
     ##
     # Return the best specification in the record that contains the file
     # matching +path+ amongst the specs that are not activated.

test/rubygems/test_require.rb

@@ -431,6 +431,22 @@ def test_default_gem_only
     assert_equal %w[default-2.0.0.0], loaded_spec_names
   end
 
+  def test_multiple_gems_with_the_same_path_the_non_activated_spec_is_chosen
+    a1 = util_spec "a", "1", nil, "lib/ib.rb"
+    a2 = util_spec "a", "2", nil, "lib/foo.rb"
+    b1 = util_spec "b", "1", nil, "lib/ib.rb"
+
+    install_specs a1, a2, b1
+
+    a2.activate
+
+    assert_equal %w[a-2], loaded_spec_names
+    assert_empty unresolved_names
+
+    assert_require "ib"
+    assert_equal %w[a-2 b-1], loaded_spec_names
+  end
+
   def test_default_gem_require_activates_just_once
     default_gem_spec = new_default_spec("default", "2.0.0.0",
                                         nil, "default/gem.rb")