Bug 839088 part 2. Add way to indicate to a CallSetup that it should propagate any exceptions thrown during the call out to the ErrorResult for the call. r=peterv

dom/bindings/CallbackObject.cpp

@@ -33,8 +33,12 @@ NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(CallbackObject)
   NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mCallback)
 NS_IMPL_CYCLE_COLLECTION_TRACE_END
 
-CallbackObject::CallSetup::CallSetup(JSObject* const aCallback)
+CallbackObject::CallSetup::CallSetup(JSObject* const aCallback,
+                                     ErrorResult& aRv,
+                                     ExceptionHandling aExceptionHandling)
   : mCx(nullptr)
+  , mErrorResult(aRv)
+  , mExceptionHandling(aExceptionHandling)
 {
   xpc_UnmarkGrayObject(aCallback);
 
@@ -123,14 +127,40 @@ CallbackObject::CallSetup::CallSetup(JSObject* const aCallback)
 
   // And now we're ready to go.
   mCx = cx;
+
+  // Make sure the JS engine doesn't report exceptions we want to re-throw
+  if (mExceptionHandling == eRethrowExceptions) {
+    mSavedJSContextOptions = JS_GetOptions(cx);
+    JS_SetOptions(cx, mSavedJSContextOptions | JSOPTION_DONT_REPORT_UNCAUGHT);
+  }
 }
 
 CallbackObject::CallSetup::~CallSetup()
 {
   // First things first: if we have a JSContext, report any pending
-  // errors on it.
+  // errors on it, unless we were told to re-throw them.
   if (mCx) {
-    nsJSUtils::ReportPendingException(mCx);
+    bool dealtWithPendingException = false;
+    if (mExceptionHandling == eRethrowExceptions) {
+      // Restore the old context options
+      JS_SetOptions(mCx, mSavedJSContextOptions);
+      mErrorResult.MightThrowJSException();
+      if (JS_IsExceptionPending(mCx)) {
+        JS::Value exn;
+        if (JS_GetPendingException(mCx, &exn)) {
+          mErrorResult.ThrowJSException(mCx, exn);
+          JS_ClearPendingException(mCx);
+          dealtWithPendingException = true;
+        }
+      }
+    }
+
+    if (!dealtWithPendingException) {
+      // Either we're supposed to report our exceptions, or we're supposed to
+      // re-throw them but we failed to JS_GetPendingException.  Either way,
+      // just report the pending exception, if any.
+      nsJSUtils::ReportPendingException(mCx);
+    }
   }
 
   // If we have an mCtx, we need to call ScriptEvaluated() on it.  But we have

dom/bindings/CallbackObject.h

@@ -81,6 +81,11 @@ public:
     return mCallback;
   }
 
+  enum ExceptionHandling {
+    eReportExceptions,
+    eRethrowExceptions
+  };
+
 protected:
   explicit CallbackObject(CallbackObject* aCallbackFunction)
     : mCallback(aCallbackFunction->mCallback)
@@ -112,7 +117,8 @@ protected:
      * non-null.
      */
   public:
-    CallSetup(JSObject* const aCallable);
+    CallSetup(JSObject* const aCallable, ErrorResult& aRv,
+              ExceptionHandling aExceptionHandling);
     ~CallSetup();
 
     JSContext* GetContext() const
@@ -149,6 +155,12 @@ protected:
     // JSContext.  Though in practice we'll often manually order those two
     // things.
     Maybe<JSAutoCompartment> mAc;
+
+    // An ErrorResult to possibly re-throw exceptions on and whether
+    // we should re-throw them.
+    ErrorResult& mErrorResult;
+    const ExceptionHandling mExceptionHandling;
+    uint32_t mSavedJSContextOptions;
   };
 };
 

dom/bindings/Codegen.py

@@ -7707,7 +7707,7 @@ class CGCallback(CGClass):
         argsWithoutThis = list(args)
         args.insert(0, Argument("const T&",  "thisObj"))
 
-        setupCall = ("CallSetup s(mCallback);\n"
+        setupCall = ("CallSetup s(mCallback, aRv, eReportExceptions);\n"
                      "if (!s.GetContext()) {\n"
                      "  aRv.Throw(NS_ERROR_UNEXPECTED);\n"
                      "  return${errorReturn};\n"
@@ -7970,7 +7970,7 @@ class CallbackMember(CGNativeMember):
             # It's been done for us already
             return ""
         return string.Template(
-            "CallSetup s(mCallback);\n"
+            "CallSetup s(mCallback, aRv, eReportExceptions);\n"
             "JSContext* cx = s.GetContext();\n"
             "if (!cx) {\n"
             "  aRv.Throw(NS_ERROR_UNEXPECTED);\n"