Implement hasMetaParents/getMetaParents for RubyClass

Author: eregon

spec/truffle/interop/meta_object_spec.rb

@@ -9,7 +9,6 @@
 require_relative '../../ruby/spec_helper'
 
 describe "Truffle::Interop.meta_object" do
-
   it "returns Integer class for an integer" do
     Truffle::Interop.meta_object(14).should == Integer
   end
@@ -30,4 +29,15 @@
     Truffle::Interop.meta_object([1, 2, 3]).should == Array
   end
 
+  it "returns a Ruby class implementing all meta objects methods" do
+    meta = Truffle::Interop.meta_object("string")
+    Truffle::Interop.meta_simple_name(meta).should == 'String'
+    Truffle::Interop.meta_qualified_name(meta).should == 'String'
+    Truffle::Interop.meta_parents(meta).to_a.should == [Object]
+
+    Truffle::Interop.meta_simple_name(Enumerator::Lazy).should == 'Lazy'
+    Truffle::Interop.meta_qualified_name(Enumerator::Lazy).should == 'Enumerator::Lazy'
+
+    Truffle::Interop.should_not.has_meta_parents?(Enumerable)
+  end
 end

src/main/java/org/truffleruby/core/klass/RubyClass.java

@@ -13,9 +13,13 @@
 import java.util.Set;
 
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
+import com.oracle.truffle.api.interop.InteropLibrary;
+import com.oracle.truffle.api.library.ExportLibrary;
+import com.oracle.truffle.api.library.ExportMessage;
 import com.oracle.truffle.api.source.SourceSection;
 import org.truffleruby.RubyLanguage;
 import org.truffleruby.core.module.RubyModule;
+import org.truffleruby.debug.SingleElementArray;
 import org.truffleruby.language.RubyDynamicObject;
 import org.truffleruby.language.objects.ObjectGraph;
 import org.truffleruby.language.objects.ObjectGraphNode;
@@ -24,6 +28,7 @@
 
 import static org.truffleruby.language.RubyBaseNode.nil;
 
+@ExportLibrary(InteropLibrary.class)
 public final class RubyClass extends RubyModule implements ObjectGraphNode {
 
     private static final RubyClass[] EMPTY_CLASS_ARRAY = new RubyClass[0];
@@ -118,4 +123,16 @@ public void getAdjacentObjects(Set<Object> reachable) {
         ObjectGraph.addProperty(reachable, superclass);
     }
 
+    // region MetaObject
+    @ExportMessage
+    public boolean hasMetaParents() {
+        return true;
+    }
+
+    @ExportMessage
+    public Object getMetaParents() {
+        return new SingleElementArray(superclass);
+    }
+    // endregion
+
 }

src/main/java/org/truffleruby/debug/SingleElementArray.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2022 Oracle and/or its affiliates. All rights reserved. This
+ * code is released under a tri EPL/GPL/LGPL license. You can use it,
+ * redistribute it and/or modify it under the terms of the:
+ *
+ * Eclipse Public License version 2.0, or
+ * GNU General Public License version 2, or
+ * GNU Lesser General Public License version 2.1.
+ */
+package org.truffleruby.debug;
+
+import com.oracle.truffle.api.dsl.Cached;
+import com.oracle.truffle.api.interop.InteropLibrary;
+import com.oracle.truffle.api.interop.InvalidArrayIndexException;
+import com.oracle.truffle.api.interop.TruffleObject;
+import com.oracle.truffle.api.library.ExportLibrary;
+import com.oracle.truffle.api.library.ExportMessage;
+import com.oracle.truffle.api.profiles.BranchProfile;
+
+@ExportLibrary(InteropLibrary.class)
+public class SingleElementArray implements TruffleObject {
+
+    private final Object element;
+
+    public SingleElementArray(Object element) {
+        this.element = element;
+    }
+
+    @ExportMessage
+    protected boolean hasArrayElements() {
+        return true;
+    }
+
+    @ExportMessage
+    protected long getArraySize() {
+        return 1;
+    }
+
+    @ExportMessage
+    protected Object readArrayElement(long index,
+            @Cached BranchProfile errorProfile) throws InvalidArrayIndexException {
+        if (isArrayElementReadable(index)) {
+            return element;
+        } else {
+            errorProfile.enter();
+            throw InvalidArrayIndexException.create(index);
+        }
+    }
+
+    @ExportMessage
+    protected boolean isArrayElementReadable(long index) {
+        return index == 0;
+    }
+
+}