src: fix delete operator on vm context

In the implementation of the vm module,
if a property is successfully deleted
on the sandbox, we also need to delete it
on the global_proxy object. Therefore, we
must not call args.GetReturnValue().Set().

We only intercept, i.e., call
args.GetReturnValue().Set(), in the
DeleterCallback, if Delete() failed, e.g. because
the property was read only.

Fixes #6287

Author: fhinkel

src/node_contextify.cc

@@ -456,8 +456,12 @@ class ContextifyContext {
 
     Maybe<bool> success = ctx->sandbox()->Delete(ctx->context(), property);
 
-    if (success.IsJust())
-      args.GetReturnValue().Set(success.FromJust());
+    if (success.FromMaybe(false))
+      return;
+
+    // Delete failed on the sandbox, intercept and do not delete on
+    // the global object.
+    args.GetReturnValue().Set(false);
   }
 
 

test/known_issues/test-vm-deleting-property.js renamed to test/parallel/test-vm-deleting-property.js

@@ -12,4 +12,4 @@ const res = vm.runInContext(`
   Object.getOwnPropertyDescriptor(this, 'x');
 `, context);
 
-assert.strictEqual(res.value, undefined);
+assert.strictEqual(res, undefined);