Bug 987669 - Implement Xray support for the data properties on ErrorObject instances. r=gabor

js/xpconnect/src/XPCJSRuntime.cpp

@@ -87,6 +87,11 @@ const char* const XPCJSRuntime::mStrings[] = {
     "name",                 // IDX_NAME
     "undefined",            // IDX_UNDEFINED
     "",                     // IDX_EMPTYSTRING
+    "fileName",             // IDX_FILENAME
+    "lineNumber",           // IDX_LINENUMBER
+    "columnNumber",         // IDX_COLUMNNUMBER
+    "stack",                // IDX_STACK
+    "message"               // IDX_MESSAGE
 };
 
 /***************************************************************************/

js/xpconnect/src/xpcprivate.h

@@ -482,6 +482,11 @@ public:
         IDX_NAME                    ,
         IDX_UNDEFINED               ,
         IDX_EMPTYSTRING             ,
+        IDX_FILENAME                ,
+        IDX_LINENUMBER              ,
+        IDX_COLUMNNUMBER            ,
+        IDX_STACK                   ,
+        IDX_MESSAGE                 ,
         IDX_TOTAL_COUNT // just a count of the above
     };
 

js/xpconnect/wrappers/XrayWrapper.cpp

@@ -693,6 +693,33 @@ JSXrayTraits::resolveOwnProperty(JSContext *cx, const Wrapper &jsWrapper,
                     return true;
                 }
             }
+        } else if (IsErrorObjectKey(key)) {
+            // The useful state of error objects is (unfortunately) represented
+            // as own data properties per-spec. This means that we can't have a
+            // a clean representation of the data (free from tampering) without
+            // doubling the slots of Error objects, which isn't great. So we
+            // forward these properties to the underlying object and then just
+            // censor any values with the wrong type. This limits the ability
+            // of content to do anything all that confusing.
+            bool isErrorIntProperty =
+                id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_LINENUMBER) ||
+                id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_COLUMNNUMBER);
+            bool isErrorStringProperty =
+                id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_FILENAME) ||
+                id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_STACK) ||
+                id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_MESSAGE);
+            if (isErrorIntProperty || isErrorStringProperty) {
+                RootedObject waiver(cx, wrapper);
+                if (!WrapperFactory::WaiveXrayAndWrap(cx, &waiver))
+                    return false;
+                if (!JS_GetOwnPropertyDescriptorById(cx, waiver, id, desc))
+                    return false;
+                bool valueMatchesType = (isErrorIntProperty && desc.value().isInt32()) ||
+                                        (isErrorStringProperty && desc.value().isString());
+                if (desc.hasGetterOrSetter() || !valueMatchesType)
+                    FillPropertyDescriptor(desc, nullptr, 0, UndefinedValue());
+                return true;
+            }
         }
 
         // The rest of this function applies only to prototypes.
@@ -960,6 +987,15 @@ JSXrayTraits::enumerateNames(JSContext *cx, HandleObject wrapper, unsigned flags
                 if (!props.append(GetRTIdByIndex(cx, XPCJSRuntime::IDX_PROTOTYPE)))
                     return false;
             }
+        } else if (IsErrorObjectKey(key)) {
+            if (!props.append(GetRTIdByIndex(cx, XPCJSRuntime::IDX_FILENAME)) ||
+                !props.append(GetRTIdByIndex(cx, XPCJSRuntime::IDX_LINENUMBER)) ||
+                !props.append(GetRTIdByIndex(cx, XPCJSRuntime::IDX_COLUMNNUMBER)) ||
+                !props.append(GetRTIdByIndex(cx, XPCJSRuntime::IDX_STACK)) ||
+                !props.append(GetRTIdByIndex(cx, XPCJSRuntime::IDX_MESSAGE)))
+            {
+                return false;
+            }
         }
 
         // The rest of this function applies only to prototypes.