[GR-34943] Use a ConcurrentMap for @@stubs_by_name in Gem::Specification

* To fix frequent transient failures in CI.
* The proper fix will be to make Hash thread-safe instead.

Author: eregon

lib/mri/rubygems/specification.rb

@@ -181,7 +181,7 @@ class Gem::Specification < Gem::BasicSpecification
   def self.clear_specs # :nodoc:
     @@all = nil
     @@stubs = nil
-    @@stubs_by_name = {}
+    @@stubs_by_name = TruffleRuby::ConcurrentMap.new
     @@spec_with_requirable_file = {}
     @@active_stub_with_requirable_file = {}
   end
@@ -818,7 +818,9 @@ def self.stubs
       pattern = "*.gemspec"
       stubs = stubs_for_pattern(pattern, false)
 
-      @@stubs_by_name = stubs.select {|s| Gem::Platform.match_spec? s }.group_by(&:name)
+      stubs_by_name = TruffleRuby::ConcurrentMap.new
+      stubs.select {|s| Gem::Platform.match_spec? s }.group_by(&:name).each_pair { |k, v| stubs_by_name[k] = v }
+      @@stubs_by_name = stubs_by_name
       stubs
     end
   end
@@ -929,7 +931,9 @@ def self.all
   # -- wilsonb
 
   def self.all=(specs)
-    @@stubs_by_name = specs.group_by(&:name)
+    stubs_by_name = TruffleRuby::ConcurrentMap.new
+    specs.group_by(&:name).each_pair { |k, v| stubs_by_name[k] = v }
+    @@stubs_by_name = stubs_by_name
     @@all = @@stubs = specs
   end
 

test/mri/tests/rubygems/test_gem_specification.rb

@@ -996,9 +996,9 @@ def test_self_stubs_for_lazy_loading
     save_gemspec("b-1", "1", dir_standard_specs) {|s| s.name = "b" }
 
     assert_equal ["a-1"], Gem::Specification.stubs_for("a").map {|s| s.full_name }
-    assert_equal 1, Gem::Specification.class_variable_get(:@@stubs_by_name).length
+    assert_equal 1, Gem::Specification.class_variable_get(:@@stubs_by_name).size
     assert_equal ["b-1"], Gem::Specification.stubs_for("b").map {|s| s.full_name }
-    assert_equal 2, Gem::Specification.class_variable_get(:@@stubs_by_name).length
+    assert_equal 2, Gem::Specification.class_variable_get(:@@stubs_by_name).size
 
     assert_equal(
       Gem::Specification.stubs_for("a").map {|s| s.object_id },