Bug 688691. Warn when LenientThis actually causes us to not throw. r=ms2ger

content/base/public/nsDeprecatedOperationList.h

@@ -29,3 +29,4 @@ DEPRECATED_OPERATION(Components)
 DEPRECATED_OPERATION(PrefixedVisibilityAPI)
 DEPRECATED_OPERATION(NodeIteratorDetach)
 DEPRECATED_OPERATION(MozAudioData)
+DEPRECATED_OPERATION(LenientThis)

dom/bindings/BindingUtils.cpp

@@ -1688,5 +1688,15 @@ InterfaceHasInstance(JSContext* cx, JSHandleObject obj, JSMutableHandleValue vp,
   return InterfaceHasInstance(cx, obj, &vp.toObject(), bp);
 }
 
+void
+ReportLenientThisUnwrappingFailure(JSContext* cx, JS::Handle<JSObject*> obj)
+{
+  GlobalObject global(cx, obj);
+  nsCOMPtr<nsPIDOMWindow> window = do_QueryInterface(global.Get());
+  if (window && window->GetDoc()) {
+    window->GetDoc()->WarnOnceAbout(nsIDocument::eLenientThis);
+  }
+}
+
 } // namespace dom
 } // namespace mozilla

dom/bindings/BindingUtils.h

@@ -1695,6 +1695,10 @@ JSBool
 InterfaceHasInstance(JSContext* cx, JSHandleObject obj, JSMutableHandleValue vp,
                      JSBool* bp);
 
+// Helper for lenient getters/setters to report to console
+void
+ReportLenientThisUnwrappingFailure(JSContext* cx, JS::Handle<JSObject*> obj);
+
 } // namespace dom
 } // namespace mozilla
 

dom/bindings/Codegen.py

@@ -4586,6 +4586,7 @@ class CGGenericGetter(CGAbstractBindingMethod):
             name = "genericLenientGetter"
             unwrapFailureCode = (
                 "MOZ_ASSERT(!JS_IsExceptionPending(cx));\n"
+                "ReportLenientThisUnwrappingFailure(cx, obj);\n"
                 "JS_SET_RVAL(cx, vp, JS::UndefinedValue());\n"
                 "return true;")
         else:
@@ -4662,6 +4663,7 @@ class CGGenericSetter(CGAbstractBindingMethod):
             name = "genericLenientSetter"
             unwrapFailureCode = (
                 "MOZ_ASSERT(!JS_IsExceptionPending(cx));\n"
+                "ReportLenientThisUnwrappingFailure(cx, obj);\n"
                 "return true;")
         else:
             name = "genericSetter"

dom/locales/en-US/chrome/dom/dom.properties

@@ -136,3 +136,5 @@ BothCSPHeadersPresent=This site specified both an X-Content-Security-Policy/Repo
 NodeIteratorDetachWarning=Calling detach() on a NodeIterator no longer has an effect.
 # LOCALIZATION NOTE: Do not translate "Mozilla Audio Data API" and "Web Audio API".
 MozAudioDataWarning=The Mozilla Audio Data API is deprecated.  Please use the Web Audio API instead.
+# LOCALIZATION NOTE: Do not translate "LenientThis" and "this"
+LenientThisWarning=Ignoring get or set of property that has [LenientThis] because the "this" object is incorrect.