Fix deferred load errors / bug #26482

runtime/bin/loader.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 
 #include "bin/loader.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/extensions.h"
@@ skipping 195 matching lines @@
       break;
     }
 
     // Wait to be notified about new I/O results.
     ml.Wait();
   }
 }
 
 
 bool Loader::ProcessResultLocked(Loader::IOResult* result) {
-  // A negative result tag indicates a loading error occurred in the service
-  // isolate. The payload is a C string of the error message.
-  if (result->tag < 0) {
-    error_ =
-        Dart_NewUnhandledExceptionError(
-            Dart_NewStringFromUTF8(result->payload,
-                                   result->payload_length));
-
-    return false;
-  }
-
   // We have to copy everything we care about out of |result| because after
   // dropping the lock below |result| may no longer valid.
   Dart_Handle uri =
       Dart_NewStringFromCString(reinterpret_cast<char*>(result->uri));
   Dart_Handle library_uri = Dart_Null();
   if (result->library_uri != NULL) {
     library_uri =
         Dart_NewStringFromCString(reinterpret_cast<char*>(result->library_uri));
   }
+
+  // A negative result tag indicates a loading error occurred in the service
+  // isolate. The payload is a C string of the error message.
+  if (result->tag < 0) {
+    Dart_Handle library = Dart_LookupLibrary(uri);
+    Dart_Handle error = Dart_NewStringFromUTF8(result->payload,
+                                               result->payload_length);
+    // If a library with the given uri exists, give it a chance to handle
+    // the error. If the load requests stems from a deferred library load,
+    // an IO error is not fatal.
+    if ((library != Dart_Null()) && !Dart_IsError(library)) {

[hausner, 2016/06/07 21:47:05]

Is there a difference between x != Dart_Null() and !Dart_IsNull(x)?

I thought we typically use Dart_IsNull(), as you do a couple of lines below.

[Cutch, 2016/06/07 22:29:26]

No difference, but I switched to Dart_IsNull().

+      ASSERT(Dart_IsLibrary(library));
+      Dart_Handle res = Dart_LibraryHandleError(library, error);
+      if (Dart_IsNull(res)) {
+        return true;
+      }
+    }
+    // Fall through
+    error_ = Dart_NewUnhandledExceptionError(error);
+    return false;
+  }
+
+
   // Check for payload and load accordingly.
   bool is_snapshot = false;
   const uint8_t* payload = result->payload;
   intptr_t payload_length = result->payload_length;
   payload =
       DartUtils::SniffForMagicNumber(payload,
                                      &payload_length,
                                      &is_snapshot);
   Dart_Handle source = Dart_Null();
   if (!is_snapshot) {
@@ skipping 330 matching lines @@
   MutexLocker ml(&loader_infos_lock_);
   Loader* loader = LoaderForLocked(dest_port_id);
   if (loader == NULL) {
     return;
   }
   loader->QueueMessage(message);
 }
 
 }  // namespace bin
 }  // namespace dart