Add specs for ractors access to module instance variables

language/fixtures/variables.rb

@@ -154,4 +154,38 @@ class Node
       attr_accessor :left, :right
     end
   end
+
+  module RactorAccess
+    singleton_class.attr_accessor :ivar
+
+    SHAREABLE_VALUE = 3
+    UNSHAREABLE_VALUE = "3"
+    WRITE_VALUE = 4
+
+    class << self
+      def read_in_ractor(shareable = true)
+        run_in_ractor(shareable, :read)
+      end
+
+      def write_in_ractor(shareable = true)
+        run_in_ractor(shareable, :write)
+      end
+
+      def run_in_ractor(shareable, type)
+        @ivar = shareable ? SHAREABLE_VALUE : UNSHAREABLE_VALUE
+
+        r = Ractor.new(type) do |type|
+          if type == :read
+            RactorAccess.ivar
+          else
+            RactorAccess.ivar = WRITE_VALUE
+          end
+        rescue => e
+          e
+        end
+
+        r.take
+      end
+    end
+  end
 end

language/variables_spec.rb

@@ -937,3 +937,48 @@ def obj.foobar; $specs_uninitialized_global_variable_lazy ||= 42; end
     end
   end
 end
+
+describe "Module instance variables within Ractors" do
+  context "when the instance variable is shareable" do
+    ruby_version_is ""..."3.1" do
+      it "raises Isolation error if read from a non-main Ractor" do
+        result = VariablesSpecs::RactorAccess.read_in_ractor
+        result.should be_an_instance_of(Ractor::IsolationError)
+      end
+    end
+
+    ruby_version_is "3.1" do
+      it "can be read from a non-main Ractor" do
+        result = VariablesSpecs::RactorAccess.read_in_ractor
+        result.should == 3
+      end
+    end
+
+    it "raises Isolation error if written to in a non-main Ractor" do
+      result = VariablesSpecs::RactorAccess.write_in_ractor
+      result.should be_an_instance_of(Ractor::IsolationError)
+    end
+
+    it "raises no error if read/written in the main Ractor" do
+      VariablesSpecs::RactorAccess.ivar = 5
+      VariablesSpecs::RactorAccess.ivar.should == 5
+    end
+  end
+
+  context "when the instance variable is not shareable" do
+    it "raises Isolation error if read from a non-main Ractor" do
+      result = VariablesSpecs::RactorAccess.read_in_ractor(false)
+      result.should be_an_instance_of(Ractor::IsolationError)
+    end
+
+    it "raises Isolation error if written to in a non-main Ractor" do
+      result = VariablesSpecs::RactorAccess.write_in_ractor(false)
+      result.should be_an_instance_of(Ractor::IsolationError)
+    end
+
+    it "raises no error if read/written in the main Ractor" do
+      VariablesSpecs::RactorAccess.ivar = "totally different"
+      VariablesSpecs::RactorAccess.ivar.should == "totally different"
+    end
+  end
+end