[modules] Allow resolve-callback to signal failure.

src/objects.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 20316 matching lines @@
   if (module->status() == kPrepared) return true;
 
   // Obtain requested modules.
   Isolate* isolate = module->GetIsolate();
   Handle<ModuleInfo> module_info(module->info(), isolate);
   Handle<FixedArray> module_requests(module_info->module_requests(), isolate);
   Handle<FixedArray> requested_modules(module->requested_modules(), isolate);
   for (int i = 0, length = module_requests->length(); i < length; ++i) {
     Handle<String> specifier(String::cast(module_requests->get(i)), isolate);
     v8::Local<v8::Module> api_requested_module;
-    // TODO(adamk): Revisit these failure cases once d8 knows how to
-    // persist a module_map across multiple top-level module loads, as
-    // the current module is left in a "half-instantiated" state.
     if (!callback(context, v8::Utils::ToLocal(specifier),
                   v8::Utils::ToLocal(module))
              .ToLocal(&api_requested_module)) {
-      // TODO(adamk): Give this a better error message. But this is a
-      // misuse of the API anyway.
-      isolate->ThrowIllegalOperation();
+      isolate->PromoteScheduledException();
       return false;
     }
     Handle<Module> requested_module = Utils::OpenHandle(*api_requested_module);
     requested_modules->set(i, *requested_module);
   }
 
   // Recurse.
   module->set_status(kPrepared);
   for (int i = 0, length = requested_modules->length(); i < length; ++i) {
     Handle<Module> requested_module(Module::cast(requested_modules->get(i)),
@@ skipping 323 matching lines @@
       // depend on this.
       return DICTIONARY_ELEMENTS;
     }
     DCHECK_LE(kind, LAST_ELEMENTS_KIND);
     return kind;
   }
 }
 
 }  // namespace internal
 }  // namespace v8