[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

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

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

test/rubygems/test_require.rb

@@ -560,6 +560,45 @@ class TestGemRequire < Gem::TestCase
     assert_require "net/http"
   end
 
+  def test_default_gem_required_circulary_with_unresolved_gems_depending_on_it
+    net_http_old = util_spec "net-http", "0.1.1", nil, "lib/net/http.rb"
+    install_gem net_http_old
+
+    net_http_default = new_default_spec "net-http", "0.3.0", nil, "net/http.rb"
+    net_http_default_path = File.join(@tempdir, "default_gems", "lib", "net/http.rb")
+    install_default_gems net_http_default
+    File.write(net_http_default_path, 'require "net/http"')
+
+    faraday_1 = util_spec "faraday", "1", { "net-http" => ">= 0" }
+    install_gem faraday_1
+
+    faraday_2 = util_spec "faraday", "2", { "net-http" => ">= 0" }
+    install_gem faraday_2
+
+    chef = util_spec "chef", "1", { "faraday" => [">= 1", "< 3"] }, "lib/chef.rb"
+    install_gem chef
+
+    assert_require "chef"
+
+    out, err = capture_output do
+      assert_require "net/http"
+    end
+
+    assert_empty out
+
+    circular_require_warning = false
+
+    err_lines = err.split("\n").reject do |line|
+      if line.include?("circular require")
+        circular_require_warning = true
+      elsif circular_require_warning # ignore backtrace lines for circular require warning
+        circular_require_warning = line.start_with?(/[\s]/)
+      end
+    end
+
+    assert_empty err_lines
+  end
+
   def loaded_spec_names
     Gem.loaded_specs.values.map(&:full_name).sort
   end