ES6: Make function name configurable

Function name property is now standardized in ES6. It was a Mozilla proprietary
extension before. With ES6, the property was made configurable, so that it can
be used instead of another proprietary property, displayName.

This is a revert of revert c791d84112.

Last time this broke a Chrome browser test which has since been updated:

5f75a3be4c

BUG=v8:3333
LOG=N
R=mstarzinger@chromium.org,verwaest@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/977003004

Cr-Commit-Position: refs/heads/master@{#26996}

src/accessors.cc

@@ -1131,12 +1131,44 @@ void Accessors::FunctionNameGetter(
 }
 
 
+MUST_USE_RESULT static MaybeHandle<Object> SetFunctionName(
+    Isolate* isolate, Handle<JSFunction> function, Handle<Object> value) {
+  Handle<Object> old_value;
+  bool is_observed = function->map()->is_observed();
+  if (is_observed) {
+    old_value = handle(function->shared()->name(), isolate);
+  }
+
+  Handle<Name> name = isolate->factory()->name_string();
+  LookupIterator it(function, name);
+  CHECK_EQ(LookupIterator::ACCESSOR, it.state());
+  DCHECK(it.HolderIsReceiverOrHiddenPrototype());
+  it.ReconfigureDataProperty(value, it.property_details().attributes());
+  value = it.WriteDataValue(value);
+
+  if (is_observed && !old_value->SameValue(*value)) {
+    return JSObject::EnqueueChangeRecord(function, "update", name, old_value);
+  }
+
+  return value;
+}
+
+
 void Accessors::FunctionNameSetter(
     v8::Local<v8::Name> name,
     v8::Local<v8::Value> val,
     const v8::PropertyCallbackInfo<void>& info) {
-  // Function name is non writable, non configurable.
-  UNREACHABLE();
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
+  HandleScope scope(isolate);
+  Handle<Object> value = Utils::OpenHandle(*val);
+
+  if (SetPropertyOnInstanceIfInherited(isolate, info, name, value)) return;
+
+  Handle<JSFunction> object =
+      Handle<JSFunction>::cast(Utils::OpenHandle(*info.Holder()));
+  if (SetFunctionName(isolate, object, value).is_null()) {
+    isolate->OptionalRescheduleException(false);
+  }
 }
 
 

src/bootstrapper.cc

@@ -382,45 +382,47 @@ void Genesis::SetFunctionInstanceDescriptor(
   int size = IsFunctionModeWithPrototype(function_mode) ? 5 : 4;
   Map::EnsureDescriptorSlack(map, size);
 
-  PropertyAttributes attribs = static_cast<PropertyAttributes>(
-      DONT_ENUM | DONT_DELETE | READ_ONLY);
+  PropertyAttributes ro_attribs =
+      static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
+  PropertyAttributes roc_attribs =
+      static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);
 
   Handle<AccessorInfo> length =
-      Accessors::FunctionLengthInfo(isolate(), attribs);
+      Accessors::FunctionLengthInfo(isolate(), ro_attribs);
   {  // Add length.
     AccessorConstantDescriptor d(Handle<Name>(Name::cast(length->name())),
-                                 length, attribs);
+                                 length, ro_attribs);
     map->AppendDescriptor(&d);
   }
   Handle<AccessorInfo> name =
-      Accessors::FunctionNameInfo(isolate(), attribs);
+      Accessors::FunctionNameInfo(isolate(), ro_attribs);
   {  // Add name.
     AccessorConstantDescriptor d(Handle<Name>(Name::cast(name->name())), name,
-                                 attribs);
+                                 roc_attribs);
     map->AppendDescriptor(&d);
   }
   Handle<AccessorInfo> args =
-      Accessors::FunctionArgumentsInfo(isolate(), attribs);
+      Accessors::FunctionArgumentsInfo(isolate(), ro_attribs);
   {  // Add arguments.
     AccessorConstantDescriptor d(Handle<Name>(Name::cast(args->name())), args,
-                                 attribs);
+                                 ro_attribs);
     map->AppendDescriptor(&d);
   }
   Handle<AccessorInfo> caller =
-      Accessors::FunctionCallerInfo(isolate(), attribs);
+      Accessors::FunctionCallerInfo(isolate(), ro_attribs);
   {  // Add caller.
     AccessorConstantDescriptor d(Handle<Name>(Name::cast(caller->name())),
-                                 caller, attribs);
+                                 caller, ro_attribs);
     map->AppendDescriptor(&d);
   }
   if (IsFunctionModeWithPrototype(function_mode)) {
     if (function_mode == FUNCTION_WITH_WRITEABLE_PROTOTYPE) {
-      attribs = static_cast<PropertyAttributes>(attribs & ~READ_ONLY);
+      ro_attribs = static_cast<PropertyAttributes>(ro_attribs & ~READ_ONLY);
     }
     Handle<AccessorInfo> prototype =
-        Accessors::FunctionPrototypeInfo(isolate(), attribs);
+        Accessors::FunctionPrototypeInfo(isolate(), ro_attribs);
     AccessorConstantDescriptor d(Handle<Name>(Name::cast(prototype->name())),
-                                 prototype, attribs);
+                                 prototype, ro_attribs);
     map->AppendDescriptor(&d);
   }
 }
@@ -540,6 +542,8 @@ void Genesis::SetStrictFunctionInstanceDescriptor(
       static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE);
   PropertyAttributes ro_attribs =
       static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
+  PropertyAttributes roc_attribs =
+      static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);
 
   // Add length.
   if (function_mode == BOUND_FUNCTION) {
@@ -557,10 +561,10 @@ void Genesis::SetStrictFunctionInstanceDescriptor(
     map->AppendDescriptor(&d);
   }
   Handle<AccessorInfo> name =
-      Accessors::FunctionNameInfo(isolate(), ro_attribs);
+      Accessors::FunctionNameInfo(isolate(), roc_attribs);
   {  // Add name.
     AccessorConstantDescriptor d(Handle<Name>(Name::cast(name->name())), name,
-                                 ro_attribs);
+                                 roc_attribs);
     map->AppendDescriptor(&d);
   }
   {  // Add arguments.

test/mjsunit/es6/function-name-configurable.js

@@ -0,0 +1,115 @@
+// 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.
+
+function getStrictF() {
+  'use strict';
+  return function f() {};
+}
+
+
+function getSloppyF() {
+  return function f() {};
+}
+
+
+function test(testFunction) {
+  testFunction(getStrictF());
+  testFunction(getSloppyF());
+}
+
+
+function testDescriptor(f) {
+  var descr = Object.getOwnPropertyDescriptor(f, 'name');
+  assertTrue(descr.configurable);
+  assertFalse(descr.enumerable);
+  assertEquals('f', descr.value);
+  assertFalse(descr.writable);
+}
+test(testDescriptor);
+
+
+function testSet(f) {
+  f.name = 'g';
+  assertEquals('f', f.name);
+}
+test(testSet);
+
+
+function testSetStrict(f) {
+  'use strict';
+  assertThrows(function() {
+    f.name = 'g';
+  }, TypeError);
+}
+test(testSetStrict);
+
+
+function testReconfigureAsDataProperty(f) {
+  Object.defineProperty(f, 'name', {
+    value: 'g',
+  });
+  assertEquals('g', f.name);
+  Object.defineProperty(f, 'name', {
+    writable: true
+  });
+  f.name = 'h';
+  assertEquals('h', f.name);
+
+  f.name = 42;
+  assertEquals(42, f.name);
+}
+test(testReconfigureAsDataProperty);
+
+
+function testReconfigureAsAccessorProperty(f) {
+  var name = 'g';
+  Object.defineProperty(f, 'name', {
+    get: function() { return name; },
+    set: function(v) { name = v; }
+  });
+  assertEquals('g', f.name);
+  f.name = 'h';
+  assertEquals('h', f.name);
+}
+test(testReconfigureAsAccessorProperty);
+
+
+function testFunctionToString(f) {
+  Object.defineProperty(f, 'name', {
+    value: {toString: function() { assertUnreachable(); }},
+  });
+  assertEquals('function f() {}', f.toString());
+}
+test(testFunctionToString);
+
+
+(function testSetOnInstance() {
+  // This needs to come before testDelete below
+  assertTrue(Function.prototype.hasOwnProperty('name'));
+
+  function f() {}
+  delete f.name;
+  assertEquals('Empty', f.name);
+
+  f.name = 42;
+  assertEquals('Empty', f.name);  // non writable prototype property.
+  assertFalse(f.hasOwnProperty('name'));
+
+  Object.defineProperty(Function.prototype, 'name', {writable: true});
+
+  f.name = 123;
+  assertTrue(f.hasOwnProperty('name'));
+  assertEquals(123, f.name);
+})();
+
+
+(function testDelete() {
+  function f() {}
+  assertTrue(delete f.name);
+  assertFalse(f.hasOwnProperty('name'));
+  assertEquals('Empty', f.name);
+
+  assertTrue(delete Function.prototype.name);
+  assertEquals(undefined, f.name);
+})();

test/mjsunit/es7/object-observe.js

@@ -1142,7 +1142,8 @@ var properties = ["a", "1", 1, "length", "setPrototype", "name", "caller"];
 function blacklisted(obj, prop) {
   return (obj instanceof Int32Array && prop == 1) ||
          (obj instanceof Int32Array && prop === "length") ||
-         (obj instanceof ArrayBuffer && prop == 1)
+         (obj instanceof ArrayBuffer && prop == 1) ||
+         (obj instanceof Function && prop === "name");  // Has its own test.
 }
 
 for (var i in objects) for (var j in properties) {
@@ -1798,3 +1799,28 @@ for (var b1 = 0; b1 < 2; ++b1)
     for (var n = 0; n < 3; ++n)
       for (var i in mutationByIncr)
         TestFastElementsLength(mutationByIncr[i], b1 != 0, b2 != 0, 7*n, 7*n+1);
+
+
+(function TestFunctionName() {
+  reset();
+
+  function fun() {}
+  Object.observe(fun, observer.callback);
+  fun.name = 'x';  // No change. Not writable.
+  Object.defineProperty(fun, 'name', {value: 'a'});
+  Object.defineProperty(fun, 'name', {writable: true});
+  fun.name = 'b';
+  delete fun.name;
+  fun.name = 'x';  // No change. Function.prototype.name is non writable
+  Object.defineProperty(Function.prototype, 'name', {writable: true});
+  fun.name = 'c';
+  fun.name = 'c';  // Same, no update.
+  Object.deliverChangeRecords(observer.callback);
+  observer.assertCallbackRecords([
+    { object: fun, type: 'update', name: 'name', oldValue: 'fun' },
+    { object: fun, type: 'reconfigure', name: 'name'},
+    { object: fun, type: 'update', name: 'name', oldValue: 'a' },
+    { object: fun, type: 'delete', name: 'name', oldValue: 'b' },
+    { object: fun, type: 'add', name: 'name' },
+  ]);
+})();

test/mjsunit/regress/regress-1530.js

@@ -80,8 +80,9 @@ assertFalse(Object.getOwnPropertyDescriptor(f, 'prototype').writable);
 assertThrows("'use strict'; f.prototype = {}");
 assertThrows("Object.defineProperty(f, 'prototype', { value: {} })");
 
-// Verify that non-writability of other properties is respected.
-assertThrows("Object.defineProperty(f, 'name', { value: {} })");
+// Verify that non-configurability of other properties is respected, but
+// non-writability is ignored by Object.defineProperty().
+Object.defineProperty(f, 'name', { value: {} });
 assertThrows("Object.defineProperty(f, 'length', { value: {} })");
 assertThrows("Object.defineProperty(f, 'caller', { value: {} })");
 assertThrows("Object.defineProperty(f, 'arguments', { value: {} })");

test/mjsunit/regress/regress-270142.js

@@ -39,7 +39,7 @@ function g(x) {
 
 function checkNameDescriptor(f) {
   var descriptor = Object.getOwnPropertyDescriptor(f, "name");
-  assertFalse(descriptor.configurable);
+  assertTrue(descriptor.configurable);
   assertFalse(descriptor.enumerable);
   assertFalse(descriptor.writable);
 }