inspector: added NodeRuntime domain

Historically Node process sends Runtime.executionContextDestroyed
with main context as argument when it is finished.
This approach has some disadvantages. V8 prevents running some
protocol command on destroyed contexts, e.g. Runtime.evaluate
will return an error or Debugger.enable won't return a list of
scripts.
Both command might be useful for different tools, e.g. tool runs
Profiler.startPreciseCoverage and at the end of node process it
would like to get list of all scripts to match data to source code.
Or some tooling frontend would like to provide capabilities to run
commands in console when node process is finished to allow user to
inspect state of the program at exit.
This PR adds new domain: NodeRuntime. After
NodeRuntime.notifyWhenWaitingForDisconnect is enabled by at least one
client, node will send NodeRuntime.waitingForDebuggerToDisconnect
event instead of Runtime.executionContextDestroyed. Based on this
signal any protocol client can capture all required information and
then disconnect its session.

PR-URL: #27600
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

src/inspector/node_inspector.gypi

@@ -9,6 +9,8 @@
       '<(SHARED_INTERMEDIATE_DIR)/src/node/inspector/protocol/NodeWorker.h',
       '<(SHARED_INTERMEDIATE_DIR)/src/node/inspector/protocol/NodeTracing.cpp',
       '<(SHARED_INTERMEDIATE_DIR)/src/node/inspector/protocol/NodeTracing.h',
+      '<(SHARED_INTERMEDIATE_DIR)/src/node/inspector/protocol/NodeRuntime.cpp',
+      '<(SHARED_INTERMEDIATE_DIR)/src/node/inspector/protocol/NodeRuntime.h',
     ],
     'node_protocol_files': [
       '<(protocol_tool_path)/lib/Allocator_h.template',
@@ -55,6 +57,8 @@
     '../../src/inspector/main_thread_interface.h',
     '../../src/inspector/node_string.cc',
     '../../src/inspector/node_string.h',
+    '../../src/inspector/runtime_agent.cc',
+    '../../src/inspector/runtime_agent.h',
     '../../src/inspector/tracing_agent.cc',
     '../../src/inspector/tracing_agent.h',
     '../../src/inspector/worker_agent.cc',

src/inspector/node_protocol.pdl

@@ -92,3 +92,16 @@ experimental domain NodeWorker
       # Identifier of a session which sends a message.
       SessionID sessionId
       string message
+
+# Support for inspecting node process state.
+experimental domain NodeRuntime
+  # Enable the `NodeRuntime.waitingForDisconnect`.
+  command notifyWhenWaitingForDisconnect
+    parameters
+      boolean enabled
+
+  # This event is fired instead of `Runtime.executionContextDestroyed` when
+  # enabled.
+  # It is fired when the Node process finished all code execution and is
+  # waiting for all frontends to disconnect.
+  event waitingForDisconnect

src/inspector/runtime_agent.cc

@@ -0,0 +1,36 @@
+#include "runtime_agent.h"
+
+#include "env-inl.h"
+#include "inspector_agent.h"
+
+namespace node {
+namespace inspector {
+namespace protocol {
+
+RuntimeAgent::RuntimeAgent(Environment* env)
+  : notify_when_waiting_for_disconnect_(false), env_(env) {}
+
+void RuntimeAgent::Wire(UberDispatcher* dispatcher) {
+  frontend_ = std::make_unique<NodeRuntime::Frontend>(dispatcher->channel());
+  NodeRuntime::Dispatcher::wire(dispatcher, this);
+}
+
+DispatchResponse RuntimeAgent::notifyWhenWaitingForDisconnect(bool enabled) {
+  if (!env_->owns_process_state()) {
+    return DispatchResponse::Error(
+        "NodeRuntime domain can only be used through main thread sessions");
+  }
+  notify_when_waiting_for_disconnect_ = enabled;
+  return DispatchResponse::OK();
+}
+
+bool RuntimeAgent::notifyWaitingForDisconnect() {
+  if (notify_when_waiting_for_disconnect_) {
+    frontend_->waitingForDisconnect();
+    return true;
+  }
+  return false;
+}
+}  // namespace protocol
+}  // namespace inspector
+}  // namespace node

src/inspector/runtime_agent.h

@@ -0,0 +1,32 @@
+#ifndef SRC_INSPECTOR_RUNTIME_AGENT_H_
+#define SRC_INSPECTOR_RUNTIME_AGENT_H_
+
+#include "node/inspector/protocol/NodeRuntime.h"
+#include "v8.h"
+
+namespace node {
+class Environment;
+
+namespace inspector {
+namespace protocol {
+
+class RuntimeAgent : public NodeRuntime::Backend {
+ public:
+  explicit RuntimeAgent(Environment* env);
+
+  void Wire(UberDispatcher* dispatcher);
+
+  DispatchResponse notifyWhenWaitingForDisconnect(bool enabled) override;
+
+  bool notifyWaitingForDisconnect();
+
+ private:
+  std::shared_ptr<NodeRuntime::Frontend> frontend_;
+  bool notify_when_waiting_for_disconnect_;
+  Environment* env_;
+};
+}  // namespace protocol
+}  // namespace inspector
+}  // namespace node
+
+#endif  // SRC_INSPECTOR_RUNTIME_AGENT_H_

src/inspector_agent.cc

@@ -2,6 +2,7 @@
 
 #include "inspector/main_thread_interface.h"
 #include "inspector/node_string.h"
+#include "inspector/runtime_agent.h"
 #include "inspector/tracing_agent.h"
 #include "inspector/worker_agent.h"
 #include "inspector/worker_inspector.h"
@@ -221,21 +222,26 @@ class ChannelImpl final : public v8_inspector::V8Inspector::Channel,
                        std::unique_ptr<InspectorSessionDelegate> delegate,
                        std::shared_ptr<MainThreadHandle> main_thread_,
                        bool prevent_shutdown)
-      : delegate_(std::move(delegate)), prevent_shutdown_(prevent_shutdown) {
+      : delegate_(std::move(delegate)), prevent_shutdown_(prevent_shutdown),
+        retaining_context_(false) {
     session_ = inspector->connect(1, this, StringView());
     node_dispatcher_ = std::make_unique<protocol::UberDispatcher>(this);
     tracing_agent_ =
         std::make_unique<protocol::TracingAgent>(env, main_thread_);
     tracing_agent_->Wire(node_dispatcher_.get());
     worker_agent_ = std::make_unique<protocol::WorkerAgent>(worker_manager);
     worker_agent_->Wire(node_dispatcher_.get());
+    runtime_agent_ = std::make_unique<protocol::RuntimeAgent>(env);
+    runtime_agent_->Wire(node_dispatcher_.get());
   }
 
   ~ChannelImpl() override {
     tracing_agent_->disable();
     tracing_agent_.reset();  // Dispose before the dispatchers
     worker_agent_->disable();
     worker_agent_.reset();  // Dispose before the dispatchers
+    runtime_agent_->disable();
+    runtime_agent_.reset();  // Dispose before the dispatchers
   }
 
   void dispatchProtocolMessage(const StringView& message) {
@@ -264,6 +270,15 @@ class ChannelImpl final : public v8_inspector::V8Inspector::Channel,
     return prevent_shutdown_;
   }
 
+  bool notifyWaitingForDisconnect() {
+    retaining_context_ = runtime_agent_->notifyWaitingForDisconnect();
+    return retaining_context_;
+  }
+
+  bool retainingContext() {
+    return retaining_context_;
+  }
+
  private:
   void sendResponse(
       int callId,
@@ -303,12 +318,14 @@ class ChannelImpl final : public v8_inspector::V8Inspector::Channel,
     DCHECK(false);
   }
 
+  std::unique_ptr<protocol::RuntimeAgent> runtime_agent_;
   std::unique_ptr<protocol::TracingAgent> tracing_agent_;
   std::unique_ptr<protocol::WorkerAgent> worker_agent_;
   std::unique_ptr<InspectorSessionDelegate> delegate_;
   std::unique_ptr<v8_inspector::V8InspectorSession> session_;
   std::unique_ptr<protocol::UberDispatcher> node_dispatcher_;
   bool prevent_shutdown_;
+  bool retaining_context_;
 };
 
 class InspectorTimer {
@@ -511,7 +528,18 @@ class NodeInspectorClient : public V8InspectorClient {
   }
 
   void disconnectFrontend(int session_id) {
-    channels_.erase(session_id);
+    auto it = channels_.find(session_id);
+    if (it == channels_.end())
+      return;
+    bool retaining_context = it->second->retainingContext();
+    channels_.erase(it);
+    if (retaining_context) {
+      for (const auto& id_channel : channels_) {
+        if (id_channel.second->retainingContext())
+          return;
+      }
+      contextDestroyed(env_->context());
+    }
   }
 
   void dispatchMessageFromFrontend(int session_id, const StringView& message) {
@@ -608,6 +636,15 @@ class NodeInspectorClient : public V8InspectorClient {
     return false;
   }
 
+  bool notifyWaitingForDisconnect() {
+    bool retaining_context = false;
+    for (const auto& id_channel : channels_) {
+      if (id_channel.second->notifyWaitingForDisconnect())
+        retaining_context = true;
+    }
+    return retaining_context;
+  }
+
   std::shared_ptr<MainThreadHandle> getThreadHandle() {
     if (interface_ == nullptr) {
       interface_.reset(new MainThreadInterface(
@@ -774,9 +811,8 @@ void Agent::WaitForDisconnect() {
     fprintf(stderr, "Waiting for the debugger to disconnect...\n");
     fflush(stderr);
   }
-  // TODO(addaleax): Maybe this should use an at-exit hook for the Environment
-  // or something similar?
-  client_->contextDestroyed(parent_env_->context());
+  if (!client_->notifyWaitingForDisconnect())
+    client_->contextDestroyed(parent_env_->context());
   if (io_ != nullptr) {
     io_->StopAcceptingNewConnections();
     client_->waitForIoShutdown();

test/common/inspector-helper.js

@@ -191,6 +191,10 @@ class InspectorSession {
     }
   }
 
+  unprocessedNotifications() {
+    return this._unprocessedNotifications;
+  }
+
   _sendMessage(message) {
     const msg = JSON.parse(JSON.stringify(message)); // Clone!
     msg.id = this._nextId++;

test/parallel/test-inspector-waiting-for-disconnect.js

@@ -0,0 +1,45 @@
+// Flags: --expose-internals
+'use strict';
+const common = require('../common');
+
+common.skipIfInspectorDisabled();
+
+const assert = require('assert');
+const { NodeInstance } = require('../common/inspector-helper.js');
+
+function mainContextDestroyed(notification) {
+  return notification.method === 'Runtime.executionContextDestroyed' &&
+      notification.params.executionContextId === 1;
+}
+
+async function runTest() {
+  const child = new NodeInstance(['--inspect-brk=0', '-e', 'process.exit(55)']);
+  const session = await child.connectInspectorSession();
+  const oldStyleSession = await child.connectInspectorSession();
+  await oldStyleSession.send([
+    { method: 'Runtime.enable' }]);
+  await session.send([
+    { method: 'Runtime.enable' },
+    { method: 'NodeRuntime.notifyWhenWaitingForDisconnect',
+      params: { enabled: true } },
+    { method: 'Runtime.runIfWaitingForDebugger' }]);
+  await session.waitForNotification((notification) => {
+    return notification.method === 'NodeRuntime.waitingForDisconnect';
+  });
+  const receivedExecutionContextDestroyed =
+    session.unprocessedNotifications().some(mainContextDestroyed);
+  if (receivedExecutionContextDestroyed) {
+    assert.fail('When NodeRuntime enabled, ' +
+      'Runtime.executionContextDestroyed should not be sent');
+  }
+  const { result: { value } } = await session.send({
+    method: 'Runtime.evaluate', params: { expression: '42' }
+  });
+  assert.strictEqual(value, 42);
+  await session.disconnect();
+  await oldStyleSession.waitForNotification(mainContextDestroyed);
+  await oldStyleSession.disconnect();
+  assert.strictEqual((await child.expectShutdown()).exitCode, 55);
+}
+
+runTest();