Cleanup and unify Isolate::ReportPendingMessages.

Note that this is a pure cleanup CL and shouldn't have an observable
impact on the functional behavior of message reporting.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/999923004

Cr-Commit-Position: refs/heads/master@{#27276}

src/isolate.cc

@@ -1143,7 +1143,7 @@ void Isolate::ScheduleThrow(Object* exception) {
   // When scheduling a throw we first throw the exception to get the
   // error reporting if it is uncaught before rescheduling it.
   Throw(exception);
-  PropagatePendingExceptionToExternalTryCatch();
+  ReportPendingMessages();
   if (has_pending_exception()) {
     thread_local_top()->scheduled_exception_ = pending_exception();
     thread_local_top()->external_caught_exception_ = false;
@@ -1410,32 +1410,50 @@ bool Isolate::IsExternalHandlerOnTop(Object* exception) {
 void Isolate::ReportPendingMessages() {
   Object* exception = pending_exception();
 
-  // Try to propagate the exception to an external v8::TryCatch handler. If
-  // propagation was unsuccessful, then we will get another chance at reporting
-  // the pending message if the exception is re-thrown.
-  bool has_been_propagated = PropagatePendingExceptionToExternalTryCatch();
-  if (!has_been_propagated) return;
-
-  // Clear the pending message object early to avoid endless recursion.
-  Object* message_obj = thread_local_top_.pending_message_obj_;
-  clear_pending_message();
-
-  // For uncatchable exceptions we do nothing. If needed, the exception and the
-  // message have already been propagated to v8::TryCatch.
-  if (!is_catchable_by_javascript(exception)) return;
+  // Propagation is unsuccessful because there still is a JavaScript handler on
+  // top that might catch the exception and hence prevent message reporting.
+  if (IsJavaScriptHandlerOnTop(exception)) {
+    thread_local_top_.external_caught_exception_ = false;
+    return;
+  }
 
   // Determine whether the message needs to be reported to all message handlers
-  // depending on whether and external v8::TryCatch or an internal JavaScript
-  // handler is on top.
+  // depending on whether an external v8::TryCatch handler is on top.
   bool should_report_exception;
+  Object* message_obj = thread_local_top_.pending_message_obj_;
+  DCHECK(message_obj->IsJSMessageObject() || message_obj->IsTheHole());
   if (IsExternalHandlerOnTop(exception)) {
+    // Propagate the exception to an external v8::TryCatch handler.
+    if (!is_catchable_by_javascript(exception)) {
+      try_catch_handler()->can_continue_ = false;
+      try_catch_handler()->has_terminated_ = true;
+      try_catch_handler()->exception_ = heap()->null_value();
+    } else {
+      try_catch_handler()->can_continue_ = true;
+      try_catch_handler()->has_terminated_ = false;
+      try_catch_handler()->exception_ = exception;
+      // Propagate to the external try-catch only if we got an actual message.
+      if (!message_obj->IsTheHole()) {
+        try_catch_handler()->message_obj_ = message_obj;
+      }
+    }
+
     // Only report the exception if the external handler is verbose.
+    thread_local_top_.external_caught_exception_ = true;
     should_report_exception = try_catch_handler()->is_verbose_;
   } else {
-    // Report the exception if it isn't caught by JavaScript code.
-    should_report_exception = !IsJavaScriptHandlerOnTop(exception);
+    // Report the exception because it cannot be caught by JavaScript code.
+    thread_local_top_.external_caught_exception_ = false;
+    should_report_exception = true;
   }
 
+  // Clear the pending message object early to avoid endless recursion.
+  clear_pending_message();
+
+  // For uncatchable exceptions we do nothing. If needed, the exception and the
+  // message have already been propagated to v8::TryCatch.
+  if (!is_catchable_by_javascript(exception)) return;
+
   // Actually report the pending message to all message handlers.
   if (!message_obj->IsTheHole() && should_report_exception) {
     HandleScope scope(this);
@@ -1470,7 +1488,7 @@ MessageLocation Isolate::GetMessageLocation() {
 
 bool Isolate::OptionalRescheduleException(bool is_bottom_call) {
   DCHECK(has_pending_exception());
-  PropagatePendingExceptionToExternalTryCatch();
+  ReportPendingMessages();
 
   bool is_termination_exception =
       pending_exception() == heap_.termination_exception();
@@ -1950,40 +1968,6 @@ void Isolate::InitializeThreadLocal() {
 }
 
 
-bool Isolate::PropagatePendingExceptionToExternalTryCatch() {
-  Object* exception = pending_exception();
-
-  if (IsJavaScriptHandlerOnTop(exception)) {
-    thread_local_top_.external_caught_exception_ = false;
-    return false;
-  }
-
-  if (!IsExternalHandlerOnTop(exception)) {
-    thread_local_top_.external_caught_exception_ = false;
-    return true;
-  }
-
-  thread_local_top_.external_caught_exception_ = true;
-  if (!is_catchable_by_javascript(exception)) {
-    try_catch_handler()->can_continue_ = false;
-    try_catch_handler()->has_terminated_ = true;
-    try_catch_handler()->exception_ = heap()->null_value();
-  } else {
-    v8::TryCatch* handler = try_catch_handler();
-    DCHECK(thread_local_top_.pending_message_obj_->IsJSMessageObject() ||
-           thread_local_top_.pending_message_obj_->IsTheHole());
-    handler->can_continue_ = true;
-    handler->has_terminated_ = false;
-    handler->exception_ = pending_exception();
-    // Propagate to the external try-catch only if we got an actual message.
-    if (thread_local_top_.pending_message_obj_->IsTheHole()) return true;
-
-    handler->message_obj_ = thread_local_top_.pending_message_obj_;
-  }
-  return true;
-}
-
-
 void Isolate::InitializeLoggingAndCounters() {
   if (logger_ == NULL) {
     logger_ = new Logger(this);

src/isolate.h

@@ -767,13 +767,16 @@ class Isolate {
   // finally clause will behave as if the exception were consumed.
   bool PredictWhetherExceptionIsCaught(Object* exception);
 
+  // Propagate pending exception message to potential v8::TryCatch. Also call
+  // message handlers when the exception is guaranteed not to be caught.
+  void ReportPendingMessages();
+
   void ScheduleThrow(Object* exception);
   // Re-set pending message, script and positions reported to the TryCatch
   // back to the TLS for re-use when rethrowing.
   void RestorePendingMessageFromTryCatch(v8::TryCatch* handler);
   // Un-schedule an exception that was caught by a TryCatch handler.
   void CancelScheduledExceptionFromTryCatch(v8::TryCatch* handler);
-  void ReportPendingMessages();
   // Return pending location if any or unfilled structure.
   MessageLocation GetMessageLocation();
 
@@ -1215,11 +1218,6 @@ class Isolate {
 
   void FillCache();
 
-  // Propagate pending exception message to the v8::TryCatch.
-  // If there is no external try-catch or message was successfully propagated,
-  // then return true.
-  bool PropagatePendingExceptionToExternalTryCatch();
-
   // Traverse prototype chain to find out whether the object is derived from
   // the Error object.
   bool IsErrorObject(Handle<Object> obj);