[GR-14940] Expose the value in a ValueWrapper in Chrome Inspector debug.

PullRequest: truffleruby/2388

Author: aardvark179

CHANGELOG.md

@@ -3,6 +3,7 @@
 New features:
 
 * Access to local variables of the interactive Binding via language bindings is now supported: `context.getBindings("ruby").putMember("my_var", 42);` (#2030).
+* `VALUE`s in C extensions now expose the Ruby object when viewed in the debugger, as long as they have not been converted to native values.
 
 Bug fixes:
 

src/main/java/org/truffleruby/cext/ValueWrapper.java

@@ -13,13 +13,15 @@
 import org.truffleruby.cext.ValueWrapperManager.AllocateHandleNode;
 import org.truffleruby.cext.ValueWrapperManager.HandleBlock;
 import org.truffleruby.core.MarkingServiceNodes.KeepAliveNode;
+import org.truffleruby.debug.VariableNamesObject;
 import org.truffleruby.interop.TranslateInteropExceptionNode;
 
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.dsl.Cached;
 import com.oracle.truffle.api.dsl.Cached.Exclusive;
 import com.oracle.truffle.api.interop.InteropLibrary;
 import com.oracle.truffle.api.interop.TruffleObject;
+import com.oracle.truffle.api.interop.UnknownIdentifierException;
 import com.oracle.truffle.api.interop.UnsupportedMessageException;
 import com.oracle.truffle.api.library.ExportLibrary;
 import com.oracle.truffle.api.library.ExportMessage;
@@ -121,4 +123,30 @@ protected static long asPointer(ValueWrapper wrapper,
 
         return handle;
     }
+
+    @ExportMessage
+    protected boolean hasMembers() {
+        return true;
+    }
+
+    @ExportMessage
+    protected Object getMembers(boolean includeInternal) {
+        return new VariableNamesObject(new String[]{ "value" });
+    }
+
+    @ExportMessage
+    protected boolean isMemberReadable(String member) {
+        return "value".equals(member);
+    }
+
+    @ExportMessage
+    protected static Object readMember(ValueWrapper wrapper, String member,
+            @Cached @Exclusive BranchProfile errorProfile) throws UnknownIdentifierException {
+        if ("value".equals(member)) {
+            return wrapper.object;
+        } else {
+            errorProfile.enter();
+            throw UnknownIdentifierException.create(member);
+        }
+    }
 }