fix: update process.parentPort API

docs/api/process.md

@@ -135,6 +135,28 @@ Each frame has its own JavaScript context. When contextIsolation is enabled, the
 world also has a separate JavaScript context.
 This property is only available in the renderer process.
 
+### `process.parentPort`
+
+A `MessagePort` if this is a [`UtilityProcess`](utility-process.md) allowing communication
+with the parent process. Messages sent using `process.parentPort.postMessage` are available in
+the parent process using [`utilityProcess.on('message')`](utility-process.md#event-message) and messages sent
+from the parent process using [`utilityProcess.postMessage()`](utility-process.md#childpostmessagemessage-transfer) are available
+in this process using `process.parentPort.on('message')`.
+
+```js
+// Main process
+const child = new UtilityProcess(path.join(__dirname, 'test.js'))
+child.postMessage({ message: 'hello' })
+child.on('message', (ev, data) => {
+  console.log(data) // hello world!
+})
+
+// Child process
+process.parentPort.on('message', (e) => {
+  process.parentPort.postMessage(`${e.data} world!`)
+})
+```
+
 ## Methods
 
 The `process` object has the following methods:

docs/api/utility-process.md

@@ -114,6 +114,15 @@ Returns:
 Emitted when the child process has a normal termination.
 For other abnormal exit cases listen to the [`child-process-gone` event of `app`](app.md#event-child-process-gone).
 
+#### Event: 'message'
+
+Returns:
+
+* `event` Event
+* `message` any
+
+Emitted when the child process sends a message using [`process.parentPort.postMessage()`](process.md#processparentport).
+
 [`child_process.fork`]: https://nodejs.org/dist/latest-v16.x/docs/api/child_process.html#child_processforkmodulepath-args-options
 [Services API]: https://chromium.googlesource.com/chromium/src/+/master/docs/mojo_and_services.md
 [stdio]: https://nodejs.org/dist/latest/docs/api/child_process.html#optionsstdio

filenames.gni

@@ -456,6 +456,8 @@ filenames = {
     "shell/browser/net/web_request_api_interface.h",
     "shell/browser/network_hints_handler_impl.cc",
     "shell/browser/network_hints_handler_impl.h",
+    "shell/browser/node_service_host_impl.cc",
+    "shell/browser/node_service_host_impl.h",
     "shell/browser/notifications/notification.cc",
     "shell/browser/notifications/notification.h",
     "shell/browser/notifications/notification_delegate.h",

lib/utility_process/init.ts

@@ -15,6 +15,7 @@ require('../common/reset-search-paths');
 require('@electron/internal/common/init');
 
 const parentPort: NodeJS.ParentPort = new EventEmitter() as any;
+parentPort.postMessage = v8Util.getHiddenValue(process, '_postMessage');
 
 v8Util.setHiddenValue(global, 'messagechannel', {
   didReceiveMessage (event: any, ports: any[]) {

patches/chromium/.patches

@@ -124,3 +124,4 @@ fix_return_v8_value_from_localframe_requestexecutescript.patch
 create_browser_v8_snapshot_file_name_fuse.patch
 chore_posix_support_remapping_fds_when_launching_service_process.patch
 feat_remap_fds_or_inherit_handles_for_child_process.patch
+feat_support_remapping_inheriting_fds_handles_for_service_process.patch

patches/chromium/feat_support_remapping_inheriting_fds_handles_for_service_process.patch

@@ -112,7 +112,7 @@ index 5f89cc089f8cca58c4d5f5168d0cf893ab461005..99b53cd36484c7c30b273e62c2fb4193
    host->GetChildProcess()->BindServiceInterface(std::move(receiver));
  }
 diff --git a/content/browser/utility_process_host.cc b/content/browser/utility_process_host.cc
-index b96072fd917fce5cd8abb16a4ef705aea4dfe132..e85c2de6726453409d3144d3a07f48b9aacb7670 100644
+index cde30840e19c6838233a26f11549a85411f3e99a..e7092d2520396946b24f8c8f9f250590e650666b 100644
 --- a/content/browser/utility_process_host.cc
 +++ b/content/browser/utility_process_host.cc
 @@ -153,6 +153,19 @@ void UtilityProcessHost::SetExtraCommandLineSwitches(
@@ -135,7 +135,7 @@ index b96072fd917fce5cd8abb16a4ef705aea4dfe132..e85c2de6726453409d3144d3a07f48b9
  mojom::ChildProcess* UtilityProcessHost::GetChildProcess() {
    return static_cast<ChildProcessHostImpl*>(process_->GetHost())
        ->child_process();
-@@ -357,6 +370,18 @@ bool UtilityProcessHost::StartProcess() {
+@@ -356,6 +369,18 @@ bool UtilityProcessHost::StartProcess() {
      }
  #endif  // BUILDFLAG(IS_CHROMEOS_LACROS)
  
@@ -320,10 +320,10 @@ index ba4da80ea34b038d22f048d17c267c92040667c4..f31413cd670d8075419f6e74f1cefb96
  
  }  // namespace content
 diff --git a/sandbox/policy/win/sandbox_win.cc b/sandbox/policy/win/sandbox_win.cc
-index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf267b40a6bf 100644
+index 2d1a89a0bf50df40177e41010adb5b05fae10ce2..2ceadaa38ad52451b04a0f3b70eae479b9af95c4 100644
 --- a/sandbox/policy/win/sandbox_win.cc
 +++ b/sandbox/policy/win/sandbox_win.cc
-@@ -740,11 +740,9 @@ ResultCode SetupAppContainerProfile(AppContainer* container,
+@@ -864,11 +864,9 @@ ResultCode GenerateConfigForSandboxedProcess(const base::CommandLine& cmd_line,
  // command line flag.
  ResultCode LaunchWithoutSandbox(
      const base::CommandLine& cmd_line,
@@ -336,7 +336,7 @@ index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf26
    // Network process runs in a job even when unsandboxed. This is to ensure it
    // does not outlive the browser, which could happen if there is a lot of I/O
    // on process shutdown, in which case TerminateProcess can fail. See
-@@ -975,7 +973,7 @@ bool SandboxWin::InitTargetServices(TargetServices* target_services) {
+@@ -1103,7 +1101,7 @@ bool SandboxWin::InitTargetServices(TargetServices* target_services) {
  ResultCode SandboxWin::GeneratePolicyForSandboxedProcess(
      const base::CommandLine& cmd_line,
      const std::string& process_type,
@@ -345,7 +345,7 @@ index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf26
      SandboxDelegate* delegate,
      TargetPolicy* policy) {
    const base::CommandLine& launcher_process_command_line =
-@@ -995,7 +993,7 @@ ResultCode SandboxWin::GeneratePolicyForSandboxedProcess(
+@@ -1117,7 +1115,7 @@ ResultCode SandboxWin::GeneratePolicyForSandboxedProcess(
    }
  
    // Add any handles to be inherited to the policy.
@@ -353,8 +353,8 @@ index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf26
 +  for (HANDLE handle : options.handles_to_inherit)
      policy->AddHandleToShare(handle);
  
-   // Pre-startup mitigations.
-@@ -1125,6 +1123,13 @@ ResultCode SandboxWin::GeneratePolicyForSandboxedProcess(
+   if (!policy->GetConfig()->IsConfigured()) {
+@@ -1138,6 +1136,13 @@ ResultCode SandboxWin::GeneratePolicyForSandboxedProcess(
    // have no effect. These calls can fail with SBOX_ERROR_BAD_PARAMS.
    policy->SetStdoutHandle(GetStdHandle(STD_OUTPUT_HANDLE));
    policy->SetStderrHandle(GetStdHandle(STD_ERROR_HANDLE));
@@ -368,7 +368,7 @@ index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf26
  #endif
  
    if (!delegate->PreSpawnTarget(policy))
-@@ -1137,7 +1142,7 @@ ResultCode SandboxWin::GeneratePolicyForSandboxedProcess(
+@@ -1150,7 +1155,7 @@ ResultCode SandboxWin::GeneratePolicyForSandboxedProcess(
  ResultCode SandboxWin::StartSandboxedProcess(
      const base::CommandLine& cmd_line,
      const std::string& process_type,
@@ -377,7 +377,7 @@ index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf26
      SandboxDelegate* delegate,
      base::Process* process) {
    const base::ElapsedTimer timer;
-@@ -1145,7 +1150,7 @@ ResultCode SandboxWin::StartSandboxedProcess(
+@@ -1158,7 +1163,7 @@ ResultCode SandboxWin::StartSandboxedProcess(
    // Avoid making a policy if we won't use it.
    if (IsUnsandboxedProcess(delegate->GetSandboxType(), cmd_line,
                             *base::CommandLine::ForCurrentProcess())) {
@@ -386,7 +386,7 @@ index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf26
                                  process);
    }
  
-@@ -1156,7 +1161,7 @@ ResultCode SandboxWin::StartSandboxedProcess(
+@@ -1169,7 +1174,7 @@ ResultCode SandboxWin::StartSandboxedProcess(
    auto policy = g_broker_services->CreatePolicy(tag);
    auto time_policy_created = timer.Elapsed();
    ResultCode result = GeneratePolicyForSandboxedProcess(
@@ -396,10 +396,10 @@ index 73627a4c488b1658469184efe57731ca3fefdc71..054f53ab02b4eeb052b21786e8d6bf26
      return result;
    auto time_policy_generated = timer.Elapsed();
 diff --git a/sandbox/policy/win/sandbox_win.h b/sandbox/policy/win/sandbox_win.h
-index ec9cb8b12e1d7cf9bada846b99e578199e34b711..76077b4bd05068e7d3330dae5554641e09628518 100644
+index cd8b2dcd6f8eeab0bdd1fd09dcb118012ef64e60..2325e4831958564e2ae36b982bd7523621a7b763 100644
 --- a/sandbox/policy/win/sandbox_win.h
 +++ b/sandbox/policy/win/sandbox_win.h
-@@ -49,7 +49,7 @@ class SANDBOX_POLICY_EXPORT SandboxWin {
+@@ -50,7 +50,7 @@ class SANDBOX_POLICY_EXPORT SandboxWin {
    static ResultCode StartSandboxedProcess(
        const base::CommandLine& cmd_line,
        const std::string& process_type,
@@ -408,7 +408,7 @@ index ec9cb8b12e1d7cf9bada846b99e578199e34b711..76077b4bd05068e7d3330dae5554641e
        SandboxDelegate* delegate,
        base::Process* process);
  
-@@ -63,7 +63,7 @@ class SANDBOX_POLICY_EXPORT SandboxWin {
+@@ -64,7 +64,7 @@ class SANDBOX_POLICY_EXPORT SandboxWin {
    static ResultCode GeneratePolicyForSandboxedProcess(
        const base::CommandLine& cmd_line,
        const std::string& process_type,

shell/browser/api/electron_api_utility_process.cc

@@ -22,6 +22,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/service_process_host.h"
 #include "content/public/common/child_process_host.h"
+#include "content/public/common/result_codes.h"
 #include "gin/handle.h"
 #include "gin/object_template_builder.h"
 #include "gin/wrappable.h"
@@ -476,10 +477,14 @@ void UtilityProcessWrapper::PostMessage(gin::Arguments* args) {
   node_service_remote_->ReceivePostMessage(std::move(transferable_message));
 }
 
-int UtilityProcessWrapper::Kill(int signal) const {
+bool UtilityProcessWrapper::Kill() const {
   if (pid_ == base::kNullProcessId)
     return 0;
-  return uv_kill(pid_, signal);
+  base::Process process = base::Process::Open(pid_);
+  bool result = process.Terminate(content::RESULT_CODE_NORMAL_EXIT, false);
+  // Refs https://bugs.chromium.org/p/chromium/issues/detail?id=818244
+  base::EnsureProcessTerminated(process.Duplicate());
+  return result;
 }
 
 v8::Local<v8::Value> UtilityProcessWrapper::GetOSProcessId(
@@ -489,6 +494,15 @@ v8::Local<v8::Value> UtilityProcessWrapper::GetOSProcessId(
   return gin::ConvertToV8(isolate, pid_);
 }
 
+void UtilityProcessWrapper::ReceivePostMessage(
+    blink::TransferableMessage message) {
+  v8::Isolate* isolate = JavascriptEnvironment::GetIsolate();
+  v8::HandleScope handle_scope(isolate);
+  v8::Local<v8::Value> message_value =
+      electron::DeserializeV8Value(isolate, message);
+  Emit("message", message_value);
+}
+
 void UtilityProcessWrapper::HandleMessage(ReaderType type,
                                           std::vector<uint8_t> message) {
   v8::Isolate* isolate = JavascriptEnvironment::GetIsolate();

shell/browser/api/electron_api_utility_process.h

@@ -53,6 +53,7 @@ class UtilityProcessWrapper
       v8::Isolate* isolate) override;
   const char* GetTypeName() override;
 
+  void ReceivePostMessage(blink::TransferableMessage message);
   void HandleMessage(ReaderType type, std::vector<uint8_t> message);
   void ResumeReading(PipeReaderBase* pipe_io);
   void ShutdownReader(ReaderType type);
@@ -65,7 +66,7 @@ class UtilityProcessWrapper
   void OnServiceProcessLaunched(const base::Process& process);
 
   void PostMessage(gin::Arguments* args);
-  int Kill(int signal) const;
+  bool Kill() const;
   v8::Local<v8::Value> GetOSProcessId(v8::Isolate* isolate) const;
 
   base::ProcessId pid_ = base::kNullProcessId;

shell/browser/electron_browser_client.cc

@@ -96,6 +96,7 @@
 #include "shell/browser/net/proxying_websocket.h"
 #include "shell/browser/net/system_network_context_manager.h"
 #include "shell/browser/network_hints_handler_impl.h"
+#include "shell/browser/node_service_host_impl.h"
 #include "shell/browser/notifications/notification_presenter.h"
 #include "shell/browser/notifications/platform_notification_service.h"
 #include "shell/browser/protocol_registry.h"
@@ -112,6 +113,7 @@
 #include "shell/common/logging.h"
 #include "shell/common/options_switches.h"
 #include "shell/common/platform_util.h"
+#include "shell/services/node/public/mojom/node_service.mojom.h"
 #include "third_party/blink/public/common/loader/url_loader_throttle.h"
 #include "third_party/blink/public/common/tokens/tokens.h"
 #include "third_party/blink/public/common/web_preferences/web_preferences.h"
@@ -1655,6 +1657,15 @@ bool ElectronBrowserClient::ShouldEnableStrictSiteIsolation() {
   return true;
 }
 
+void ElectronBrowserClient::BindUtilityHostReceiver(
+    mojo::GenericPendingReceiver receiver) {
+  if (auto r = receiver.As<node::mojom::NodeServiceHost>()) {
+    static base::NoDestructor<NodeServiceHostImpl> node_service_host;
+    node_service_host->BindReceiver(std::move(r));
+    return;
+  }
+}
+
 void ElectronBrowserClient::BindHostReceiverForRenderer(
     content::RenderProcessHost* render_process_host,
     mojo::GenericPendingReceiver receiver) {

shell/browser/electron_browser_client.h

@@ -72,6 +72,7 @@ class ElectronBrowserClient : public content::ContentBrowserClient,
   std::string GetApplicationLocale() override;
   base::FilePath GetFontLookupTableCacheDir() override;
   bool ShouldEnableStrictSiteIsolation() override;
+  void BindUtilityHostReceiver(mojo::GenericPendingReceiver receiver) override;
   void BindHostReceiverForRenderer(
       content::RenderProcessHost* render_process_host,
       mojo::GenericPendingReceiver receiver) override;

shell/browser/node_service_host_impl.cc

@@ -0,0 +1,32 @@
+// Copyright (c) 2022 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "shell/browser/node_service_host_impl.h"
+
+#include <utility>
+
+#include "shell/browser/api/electron_api_utility_process.h"
+
+namespace electron {
+
+NodeServiceHostImpl::NodeServiceHostImpl() = default;
+
+NodeServiceHostImpl::~NodeServiceHostImpl() = default;
+
+void NodeServiceHostImpl::BindReceiver(
+    mojo::PendingReceiver<node::mojom::NodeServiceHost> receiver) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  receivers_.Add(this, std::move(receiver));
+}
+
+void NodeServiceHostImpl::ReceivePostMessage(
+    base::ProcessId pid,
+    blink::TransferableMessage message) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  auto* utility_process_wrapper = GetAllUtilityProcessWrappers().Lookup(pid);
+  if (utility_process_wrapper)
+    utility_process_wrapper->ReceivePostMessage(std::move(message));
+}
+
+}  // namespace electron

shell/browser/node_service_host_impl.h

@@ -0,0 +1,38 @@
+// Copyright (c) 2022 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ELECTRON_SHELL_BROWSER_NODE_SERVICE_HOST_IMPL_H_
+#define ELECTRON_SHELL_BROWSER_NODE_SERVICE_HOST_IMPL_H_
+
+#include "base/sequence_checker.h"
+#include "mojo/public/cpp/bindings/pending_receiver.h"
+#include "mojo/public/cpp/bindings/receiver_set.h"
+#include "shell/services/node/public/mojom/node_service.mojom.h"
+
+namespace electron {
+
+class NodeServiceHostImpl : public node::mojom::NodeServiceHost {
+ public:
+  NodeServiceHostImpl();
+
+  NodeServiceHostImpl(const NodeServiceHostImpl&) = delete;
+  NodeServiceHostImpl& operator=(const NodeServiceHostImpl&) = delete;
+
+  ~NodeServiceHostImpl() override;
+
+  void BindReceiver(
+      mojo::PendingReceiver<node::mojom::NodeServiceHost> receiver);
+
+  // node::mojom::NodeServiceHost:
+  void ReceivePostMessage(base::ProcessId pid,
+                          blink::TransferableMessage message) override;
+
+ private:
+  mojo::ReceiverSet<node::mojom::NodeServiceHost> receivers_;
+  SEQUENCE_CHECKER(sequence_checker_);
+};
+
+}  // namespace electron
+
+#endif  // ELECTRON_SHELL_BROWSER_NODE_SERVICE_HOST_IMPL_H_

shell/services/node/node_service.cc

@@ -9,12 +9,15 @@
 
 #include "base/command_line.h"
 #include "base/environment.h"
+#include "base/process/process.h"
 #include "base/strings/utf_string_conversions.h"
+#include "content/public/utility/utility_thread.h"
 #include "gin/data_object_builder.h"
 #include "gin/handle.h"
 #include "shell/browser/api/message_port.h"
 #include "shell/browser/javascript_environment.h"
 #include "shell/common/api/electron_bindings.h"
+#include "shell/common/gin_converters/callback_converter.h"
 #include "shell/common/gin_converters/file_path_converter.h"
 #include "shell/common/gin_helper/dictionary.h"
 #include "shell/common/gin_helper/event_emitter_caller.h"
@@ -33,6 +36,10 @@ NodeService::NodeService(
           std::make_unique<ElectronBindings>(node_bindings_->uv_loop())) {
   if (receiver.is_valid())
     receiver_.Bind(std::move(receiver));
+  if (auto* thread = content::UtilityThread::Get()) {
+    thread->BindHostReceiver(
+        node_service_host_remote_.BindNewPipeAndPassReceiver());
+  }
 }
 
 NodeService::~NodeService() {
@@ -82,6 +89,9 @@ void NodeService::Initialize(node::mojom::NodeServiceParamsPtr params) {
   // Add entry script to process object.
   gin_helper::Dictionary process(env->isolate(), env->process_object());
   process.SetReadOnly("_serviceStartupScript", params->script);
+  process.SetHidden("_postMessage",
+                    base::BindRepeating(&NodeService::PostMessage,
+                                        weak_factory_.GetWeakPtr()));
 
   // Load everything.
   node_bindings_->LoadEnvironment(env);
@@ -97,6 +107,17 @@ void NodeService::Initialize(node::mojom::NodeServiceParamsPtr params) {
   node_bindings_->StartPolling();
 }
 
+void NodeService::PostMessage(v8::Local<v8::Value> message_value) {
+  if (!node_service_host_remote_)
+    return;
+
+  v8::Isolate* isolate = js_env_->isolate();
+  blink::TransferableMessage transferable_message;
+  electron::SerializeV8Value(isolate, message_value, &transferable_message);
+  node_service_host_remote_->ReceivePostMessage(
+      base::Process::Current().Pid(), std::move(transferable_message));
+}
+
 void NodeService::ReceivePostMessage(blink::TransferableMessage message) {
   v8::Isolate* isolate = js_env_->isolate();
   v8::HandleScope handle_scope(isolate);

shell/services/node/node_service.h

@@ -10,8 +10,15 @@
 
 #include "mojo/public/cpp/bindings/pending_receiver.h"
 #include "mojo/public/cpp/bindings/receiver.h"
+#include "mojo/public/cpp/bindings/remote.h"
 #include "shell/services/node/public/mojom/node_service.mojom.h"
 
+namespace v8 {
+template <class T>
+class Local;
+class Value;
+}  // namespace v8
+
 namespace electron {
 
 class ElectronBindings;
@@ -29,6 +36,8 @@ class NodeService : public node::mojom::NodeService {
 
   ~NodeService() override;
 
+  void PostMessage(v8::Local<v8::Value> message_value);
+
   // mojom::NodeService implementation:
   void Initialize(node::mojom::NodeServiceParamsPtr params) override;
   void ReceivePostMessage(blink::TransferableMessage message) override;
@@ -40,8 +49,9 @@ class NodeService : public node::mojom::NodeService {
   std::unique_ptr<NodeBindings> node_bindings_;
   std::unique_ptr<ElectronBindings> electron_bindings_;
   std::unique_ptr<NodeEnvironment> node_env_;
-
+  mojo::Remote<node::mojom::NodeServiceHost> node_service_host_remote_;
   mojo::Receiver<node::mojom::NodeService> receiver_{this};
+  base::WeakPtrFactory<NodeService> weak_factory_{this};
 };
 
 }  // namespace electron

shell/services/node/public/mojom/node_service.mojom

@@ -5,6 +5,7 @@
 module node.mojom;
 
 import "mojo/public/mojom/base/file_path.mojom";
+import "mojo/public/mojom/base/process_id.mojom";
 import "sandbox/policy/mojom/sandbox.mojom";
 import "third_party/blink/public/mojom/messaging/transferable_message.mojom";
 
@@ -26,3 +27,8 @@ interface NodeService {
 
   ReceivePostMessage(blink.mojom.TransferableMessage message);
 };
+
+interface NodeServiceHost {
+  ReceivePostMessage(mojo_base.mojom.ProcessId pid,
+                     blink.mojom.TransferableMessage message);
+};

spec/api-utility-process-spec.ts

@@ -161,11 +161,9 @@ describe('UtilityProcess module', () => {
       const result = 'I will be echoed.';
       const child = new UtilityProcess(path.join(fixturesPath, 'post-message.js'));
       await emittedOnce(child, 'spawn');
-      const { port1, port2 } = new MessageChannelMain();
-      child.postMessage(result, [port2]);
-      port1.start();
-      const [e] = await emittedOnce(port1, 'message');
-      expect(e.data).to.equal(result);
+      child.postMessage(result);
+      const [, data] = await emittedOnce(child, 'message');
+      expect(data).to.equal(result);
       const exit = emittedOnce(child, 'exit');
       expect(child.kill()).to.be.true();
       await exit;
@@ -263,17 +261,13 @@ describe('UtilityProcess module', () => {
       await w.loadFile(path.join(__dirname, 'fixtures', 'blank.html'));
       // Create Message port pair for Renderer <-> Utility Process.
       const { port1: rendererPort, port2: childPort1 } = new MessageChannelMain();
-      // Create Message port pair for Utility Process <-> Main.
-      const { port1: mainPort, port2: childPort2 } = new MessageChannelMain();
       w.webContents.postMessage('port', result, [rendererPort]);
       // Send renderer and main channel port to utility process.
       const child = new UtilityProcess(path.join(fixturesPath, 'receive-message.js'));
       await emittedOnce(child, 'spawn');
-      child.postMessage('', [childPort1, childPort2]);
-      // Receive result from utility process.
-      mainPort.start();
-      const [e] = await emittedOnce(mainPort, 'message');
-      expect(e.data).to.equal(result);
+      child.postMessage('', [childPort1]);
+      const [, data] = await emittedOnce(child, 'message');
+      expect(data).to.equal(result);
       // Cleanup.
       const exit = emittedOnce(child, 'exit');
       expect(child.kill()).to.be.true();

spec/fixtures/api/utility-process/post-message.js

@@ -1,3 +1,3 @@
 process.parentPort.on('message', (e) => {
-  e.ports[0].postMessage(e.data);
+  process.parentPort.postMessage(e.data);
 });

spec/fixtures/api/utility-process/receive-message.js

@@ -1,6 +1,6 @@
 process.parentPort.on('message', (e) => {
   e.ports[0].on('message', (ev) => {
-    e.ports[1].postMessage(ev.data);
+    process.parentPort.postMessage(ev.data);
   });
   e.ports[0].start();
 });