[rubygems/rubygems] Fix activation conflicts when circularly requiring a gem

If a gem is required circular, and there are unresolved specs depending
on it, we may end up in an activation conflict.

The solution is to not try to activate unresolved gems when requiring a
default gem, regardless of it having already been activated or not.

https://github.com/rubygems/rubygems/commit/3b2b8f4e3e

2 files changed, 13 insertions, 2 deletions

diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index 47b1ce69d2..ad7ab10756 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -1216,6 +1216,13 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
     ##
     # Find a Gem::Specification of default gem from +path+
 
+    def find_default_spec(path)
+      @path_to_default_spec_map[path]
+    end
+
+    ##
+    # Find an unresolved Gem::Specification of default gem from +path+
+
     def find_unresolved_default_spec(path)
       default_spec = @path_to_default_spec_map[path]
       default_spec if default_spec && loaded_specs[default_spec.name] != default_spec
diff --git a/lib/rubygems/core_ext/kernel_require.rb b/lib/rubygems/core_ext/kernel_require.rb
index 50e3ea89b4..073966b696 100644
--- a/lib/rubygems/core_ext/kernel_require.rb
+++ b/lib/rubygems/core_ext/kernel_require.rb
@@ -42,7 +42,11 @@ module Kernel
       # If +path+ belongs to a default gem, we activate it and then go straight
       # to normal require
 
-      if spec = Gem.find_unresolved_default_spec(path)
+      if spec = Gem.find_default_spec(path)
+        name = spec.name
+
+        next if Gem.loaded_specs[name]
+
         # Ensure -I beats a default gem
         resolved_path = begin
           rp = nil
@@ -60,7 +64,7 @@ module Kernel
           rp
         end
 
-        Kernel.send(:gem, spec.name, Gem::Requirement.default_prerelease) unless
+        Kernel.send(:gem, name, Gem::Requirement.default_prerelease) unless
           resolved_path
 
         next