Fix singleton class lookup bug when singleton class is replaced on the instance.

Co-authored-by: Kevin Menard <[email protected]>
Co-authored-by: Peter Arato <[email protected]>

Author: itarato

CHANGELOG.md

@@ -6,6 +6,7 @@ New features:
 Bug fixes:
 
 * Fix `Dir.glob` returning blank string entry with leading `**/` in glob and `base:` argument (@rwstauner).
+* Fixing singleton class lookup after an object's singleton class has been replaced (@itarato).
 
 Compatibility:
 

spec/ruby/language/method_spec.rb

@@ -176,6 +176,22 @@ def m(x)
       m('a', &nil).should == [false]
     end
   end
+
+  context "with a replaced singleton class" do
+    it "looks up singleton methods from the fresh singleton class after an object instance got a new one" do
+      require "socket"
+      proxy = -> (io) { io.foo }
+
+      io = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM)
+      io.define_singleton_method(:foo) { "old" }
+      proxy.call(io).should == "old"
+
+      # `IO#reopen` is an example where an object's singleton class is replaced.
+      io.reopen(Socket.new(Socket::AF_INET, Socket::SOCK_STREAM))
+      io.define_singleton_method(:foo) { "new" }
+      proxy.call(io).should == "new"
+    end
+  end
 end
 
 describe "An element assignment method send" do

src/main/java/org/truffleruby/core/VMPrimitiveNodes.java

@@ -68,6 +68,7 @@
 import org.truffleruby.core.proc.ProcOperations;
 import org.truffleruby.core.proc.RubyProc;
 import org.truffleruby.core.string.RubyString;
+import org.truffleruby.core.support.RubyIO;
 import org.truffleruby.core.symbol.RubySymbol;
 import org.truffleruby.core.thread.RubyThread;
 import org.truffleruby.extra.ffi.Pointer;
@@ -425,7 +426,7 @@ public abstract static class VMSetClassNode extends PrimitiveArrayArgumentsNode
 
         @TruffleBoundary
         @Specialization
-        protected RubyDynamicObject setClass(RubyDynamicObject object, RubyClass newClass) {
+        protected RubyDynamicObject setClass(RubyIO object, RubyClass newClass) {
             SharedObjects.propagate(getLanguage(), object, newClass);
             synchronized (object) {
                 object.setMetaClass(newClass);

src/main/java/org/truffleruby/language/RubyGuards.java

@@ -33,6 +33,7 @@
 import org.truffleruby.core.regexp.RubyRegexp;
 import org.truffleruby.core.string.ImmutableRubyString;
 import org.truffleruby.core.string.RubyString;
+import org.truffleruby.core.support.RubyIO;
 import org.truffleruby.core.symbol.RubySymbol;
 import org.truffleruby.interop.ToJavaStringNode;
 import org.truffleruby.language.arguments.ArgumentsDescriptor;
@@ -137,6 +138,11 @@ public static boolean isRubyModule(Object value) {
         return value instanceof RubyModule;
     }
 
+    @Idempotent
+    public static boolean isRubyIO(Object value) {
+        return value instanceof RubyIO;
+    }
+
     public static boolean isRubyRegexp(Object value) {
         return value instanceof RubyRegexp;
     }

src/main/java/org/truffleruby/language/objects/MetaClassNode.java

@@ -42,7 +42,11 @@ public final RubyClass executeCached(Object value) {
     public abstract RubyClass execute(Node node, Object value);
 
     @Specialization(
-            guards = { "isSingleContext()", "object == cachedObject", "metaClass.isSingleton" },
+            guards = {
+                    "isSingleContext()",
+                    "object == cachedObject",
+                    "metaClass.isSingleton",
+                    "!isRubyIO(cachedObject)" },
             limit = "1")
     protected static RubyClass singleton(Node node, RubyDynamicObject object,
             @Cached("object") RubyDynamicObject cachedObject,