[modules] Implement namespace imports.

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 6536 matching lines @@
                                           PropertyDescriptor* desc,
                                           ShouldThrow should_throw) {
   if (object->IsJSArray()) {
     return JSArray::DefineOwnProperty(isolate, Handle<JSArray>::cast(object),
                                       key, desc, should_throw);
   }
   if (object->IsJSProxy()) {
     return JSProxy::DefineOwnProperty(isolate, Handle<JSProxy>::cast(object),
                                       key, desc, should_throw);
   }
-  // TODO(jkummerow): Support Modules (ES6 9.4.6.6)
+  // TODO(neis): Special case for JSModuleNamespace?
 
   // OrdinaryDefineOwnProperty, by virtue of calling
   // DefineOwnPropertyIgnoreAttributes, can handle arguments (ES6 9.4.4.2)
   // and IntegerIndexedExotics (ES6 9.4.5.3), with one exception:
   // TODO(jkummerow): Setting an indexed accessor on a typed array should throw.
   return OrdinaryDefineOwnProperty(isolate, Handle<JSObject>::cast(object), key,
                                    desc, should_throw);
 }
 
 
@@ skipping 11662 matching lines @@
   DCHECK(IsKey(isolate, *key));
 
   // If the object does not have an identity hash, it was never used as a key.
   Object* hash = key->GetHash();
   if (hash->IsUndefined(isolate)) {
     return isolate->heap()->the_hole_value();
   }
   return Lookup(isolate, key, Smi::cast(hash)->value());
 }
 
+Object* ObjectHashTable::ValueAt(int entry) {
+  return get(EntryToValueIndex(entry));
+}
 
 Object* ObjectHashTable::Lookup(Handle<Object> key, int32_t hash) {
   return Lookup(GetIsolate(), key, hash);
 }
 
 
 Handle<ObjectHashTable> ObjectHashTable::Put(Handle<ObjectHashTable> table,
                                              Handle<Object> key,
                                              Handle<Object> value) {
   Isolate* isolate = table->GetIsolate();
@@ skipping 1327 matching lines @@
 
 bool JSReceiver::HasProxyInPrototype(Isolate* isolate) {
   for (PrototypeIterator iter(isolate, this, kStartAtReceiver,
                               PrototypeIterator::END_AT_NULL);
        !iter.IsAtEnd(); iter.AdvanceIgnoringProxies()) {
     if (iter.GetCurrent<Object>()->IsJSProxy()) return true;
   }
   return false;
 }
 
+Object* JSModuleNamespace::Get(Handle<String> name) {
+  Isolate* isolate = name->GetIsolate();
+  Handle<Object> object(module()->exports()->Lookup(name), isolate);
+  return object->IsTheHole(isolate) ? isolate->heap()->undefined_value()
+                                    : Handle<Cell>::cast(object)->value();
+}
+
 namespace {
 
 template <typename T>
 struct HandleValueHash {
   V8_INLINE size_t operator()(Handle<T> handle) const { return handle->Hash(); }
 };
 
 struct ModuleHandleEqual {
   V8_INLINE bool operator()(Handle<Module> lhs, Handle<Module> rhs) const {
     return *lhs == *rhs;
@@ skipping 11 matching lines @@
                                 StringHandleEqual,
                                 zone_allocator<Handle<String>>> {
  public:
   explicit UnorderedStringSet(Zone* zone)
       : std::unordered_set<Handle<String>, HandleValueHash<String>,
                            StringHandleEqual, zone_allocator<Handle<String>>>(
             2 /* bucket count */, HandleValueHash<String>(),
             StringHandleEqual(), zone_allocator<Handle<String>>(zone)) {}
 };
 
+class UnorderedModuleSet
+    : public std::unordered_set<Handle<Module>, HandleValueHash<Module>,
+                                ModuleHandleEqual,
+                                zone_allocator<Handle<Module>>> {
+ public:
+  explicit UnorderedModuleSet(Zone* zone)
+      : std::unordered_set<Handle<Module>, HandleValueHash<Module>,
+                           ModuleHandleEqual, zone_allocator<Handle<Module>>>(
+            2 /* bucket count */, HandleValueHash<Module>(),
+            ModuleHandleEqual(), zone_allocator<Handle<Module>>(zone)) {}
+};
+
+class UnorderedStringMap
+    : public std::unordered_map<
+          Handle<String>, Handle<Object>, HandleValueHash<String>,
+          StringHandleEqual,
+          zone_allocator<std::pair<const Handle<String>, Handle<Object>>>> {
+ public:
+  explicit UnorderedStringMap(Zone* zone)
+      : std::unordered_map<
+            Handle<String>, Handle<Object>, HandleValueHash<String>,
+            StringHandleEqual,
+            zone_allocator<std::pair<const Handle<String>, Handle<Object>>>>(
+            2 /* bucket count */, HandleValueHash<String>(),
+            StringHandleEqual(),
+            zone_allocator<std::pair<const Handle<String>, Handle<Object>>>(
+                zone)) {}
+};
+
 }  // anonymous namespace
 
 class Module::ResolveSet
     : public std::unordered_map<
           Handle<Module>, UnorderedStringSet*, HandleValueHash<Module>,
           ModuleHandleEqual, zone_allocator<std::pair<const Handle<Module>,
                                                       UnorderedStringSet*>>> {
  public:
   explicit ResolveSet(Zone* zone)
       : std::unordered_map<Handle<Module>, UnorderedStringSet*,
@@ skipping 303 matching lines @@
     Handle<Module> import(Module::cast(requested_modules->get(i)), isolate);
     RETURN_ON_EXCEPTION(isolate, Evaluate(import), Object);
   }
 
   // Evaluation of module body.
   Handle<JSFunction> resume(
       isolate->native_context()->generator_next_internal(), isolate);
   return Execution::Call(isolate, resume, generator, 0, nullptr);
 }
 
+namespace {

[adamk, 2016/10/04 18:26:53]

Please add a blank line after this (and before the closing })

[neis, 2016/10/05 08:18:41]

Done.

+void FetchStarExports(Handle<Module> module, Zone* zone,
+                      UnorderedModuleSet* visited) {
+  DCHECK(module->code()->IsJSFunction());  // Instantiated.
+
+  bool cycle = !visited->insert(module).second;
+  if (cycle) return;
+
+  Isolate* isolate = module->GetIsolate();
+  Handle<ObjectHashTable> exports(module->exports(), isolate);
+  UnorderedStringMap more_exports(zone);
+
+  // TODO(neis): Only allocate more_exports if there are star exports.
+  // Maybe split special_exports into indirect_exports and star_exports.
+
+  Handle<FixedArray> special_exports(module->info()->special_exports(),
+                                     isolate);
+  for (int i = 0, n = special_exports->length(); i < n; ++i) {
+    i::Handle<i::ModuleInfoEntry> entry(

[adamk, 2016/10/04 18:26:53]

No need for i:: prefixes here (and below).

[neis, 2016/10/05 08:18:41]

Done.

+        i::ModuleInfoEntry::cast(special_exports->get(i)), isolate);
+    if (!entry->export_name()->IsUndefined(isolate)) {
+      continue;  // Indirect export.
+    }
+
+    int module_request = Smi::cast(entry->module_request())->value();
+    Handle<Module> requested_module(
+        Module::cast(module->requested_modules()->get(module_request)),
+        isolate);
+
+    // Recurse.
+    FetchStarExports(requested_module, zone, visited);
+
+    // Collect all of [requested_module]'s exports that must be added to
+    // [module]'s exports (i.e. to [exports]).  We record these in
+    // [more_exports].  Ambiguities (conflicting exports) are marked by mapping
+    // the name to undefined instead of a Cell.
+    Handle<ObjectHashTable> requested_exports(requested_module->exports(),
+                                              isolate);
+    for (int i = 0, n = requested_exports->Capacity(); i < n; ++i) {
+      Handle<Object> key(requested_exports->KeyAt(i), isolate);
+      if (!requested_exports->IsKey(isolate, *key)) continue;
+      if (Handle<String>::cast(key)->Equals(isolate->heap()->default_string()))
+        continue;
+      if (!exports->Lookup(key)->IsTheHole(isolate)) continue;
+
+      Handle<String> name = Handle<String>::cast(key);
+      Handle<Cell> cell(Cell::cast(requested_exports->ValueAt(i)), isolate);
+      auto it = more_exports.find(name);
+      if (it == more_exports.end()) {
+        more_exports.insert(std::make_pair(name, cell));

[adamk, 2016/10/04 18:26:53]

Please change this code to only do a single lookup, using insert() and using
result.first->second, etc.

[neis, 2016/10/05 08:18:41]

Done.

+      } else if (*it->second == *cell || it->second->IsUndefined(isolate)) {
+        // We already recorded this mapping, or the name is ambiguous.  In
+        // either case, there's nothing to do.
+      } else {
+        DCHECK(it->second->IsCell());
+        // Different star exports provide different cells for this name, hence
+        // mark the name as ambiguous.
+        it->second = isolate->factory()->undefined_value();
+      }
+    }
+  }
+
+  // Copy [more_exports] into [exports].
+  for (const auto& elem : more_exports) {
+    if (elem.second->IsUndefined(isolate)) continue;  // Ambiguous export.
+    DCHECK(!elem.first->Equals(isolate->heap()->default_string()));
+    DCHECK(elem.second->IsCell());
+    exports = ObjectHashTable::Put(exports, elem.first, elem.second);
+  }
+  module->set_exports(*exports);
+}
+}  // anonymous namespace
+
+void Module::FetchStarExports(Handle<Module> module, Zone* zone) {

[adamk, 2016/10/04 18:26:53]

Is this called anywhere other than below? Maybe just inline it there? That'd
avoid the confusion of the same-named functions.

[neis, 2016/10/05 08:18:41]

Ok, inlined it.

+  UnorderedModuleSet visited(zone);
+  return i::FetchStarExports(module, zone, &visited);
+}
+
+Handle<JSModuleNamespace> Module::GetModuleNamespace(Handle<Module> module,
+                                                     int module_request) {
+  Isolate* isolate = module->GetIsolate();
+  Handle<Module> requested_module(
+      Module::cast(module->requested_modules()->get(module_request)), isolate);
+  return Module::GetModuleNamespace(requested_module);
+}
+
+Handle<JSModuleNamespace> Module::GetModuleNamespace(Handle<Module> module) {
+  Isolate* isolate = module->GetIsolate();
+
+  Handle<HeapObject> object(module->module_namespace(), isolate);
+  if (!object->IsUndefined(isolate)) {
+    // Namespace object already exists.
+    return Handle<JSModuleNamespace>::cast(object);
+  }
+
+  // Create the namespace object (initially empty).
+  Handle<JSModuleNamespace> ns = isolate->factory()->NewJSModuleNamespace();
+  ns->set_module(*module);
+  module->set_module_namespace(*ns);
+
+  // Collect the export names.
+  Zone zone(isolate->allocator());
+  FetchStarExports(module, &zone);
+  Handle<ObjectHashTable> exports(module->exports(), isolate);
+  ZoneVector<Handle<String>> names(&zone);
+  names.reserve(exports->NumberOfElements());
+  for (int i = 0, n = exports->Capacity(); i < n; ++i) {
+    Handle<Object> key(exports->KeyAt(i), isolate);
+    if (!exports->IsKey(isolate, *key)) continue;
+    DCHECK(exports->ValueAt(i)->IsCell());
+    names.push_back(Handle<String>::cast(key));
+  }
+  DCHECK_EQ(names.size(), exports->NumberOfElements());
+
+  // Sort them alphabetically.
+  struct {
+    bool operator()(Handle<String> a, Handle<String> b) {
+      return String::Compare(a, b) == ComparisonResult::kLessThan;
+    }
+  } StringLess;
+  std::sort(names.begin(), names.end(), StringLess);
+
+  // Create the corresponding properties in the namespace object.
+  PropertyAttributes attr = DONT_DELETE;
+  for (const auto& name : names) {
+    JSObject::SetAccessor(
+        ns, Accessors::ModuleNamespaceEntryInfo(isolate, name, attr))
+        .Check();
+  }
+  JSObject::PreventExtensions(ns, THROW_ON_ERROR).ToChecked();
+
+  return ns;
+}
+
 }  // namespace internal
 }  // namespace v8