Add metrics for devtools IPL (#1404)

* Add metrics for devtools IPL

* Addressed CR comments

* Addressed CR comments

* Removed gathering stats on getObject

* Updated old metrics to call _withEvent, added tests

* Moved creation of events to DwdsEvents class

* Add ext.dwds.sendEvent service extension to implement  DEBUGGER_READY event

* Generalize devtools events to support multiple screens

* Support 'action' field in Devtools event payload

* Make tests to fail on timeout with a descriptive message

* Addressed CR comments about test structure

Author: Anna Gringauze

dwds/CHANGELOG.md

@@ -1,3 +1,29 @@
+## 11.3.1-dev
+
+- Add metrics measuring DevTools Initial Page Load time.
+- Add `ext.dwds.sendEvent` service extension to dwds so other tools
+  can send events to the debugger.
+  Event format:
+  ```
+  {
+    'type': '<event type>',
+    'payload': {
+      'screen: '<screen name>',
+      'action: '<action name>',
+    }
+  }
+  ```
+  Currently supported event values:
+  ```
+  {
+    'type: 'DevtoolsEvent',
+    'payload': {
+      'screen': 'debugger'
+      'action': 'screenReady'
+    }
+  }
+  ```
+
 ## 11.3.0
 
 - Update SDK constraint to `>=2.14.0 <3.0.0`

dwds/lib/src/dwds_vm_client.dart

@@ -40,7 +40,8 @@ class DwdsVmClient {
         await client.dispose();
       }();
 
-  static Future<DwdsVmClient> create(DebugService debugService) async {
+  static Future<DwdsVmClient> create(
+      DebugService debugService, DwdsStats dwdsStats) async {
     // Set up hot restart as an extension.
     var requestController = StreamController<Map<String, Object>>();
     var responseController = StreamController<Map<String, Object>>();
@@ -154,6 +155,12 @@ class DwdsVmClient {
     });
     await client.registerService('ext.dwds.screenshot', 'DWDS');
 
+    client.registerServiceCallback('ext.dwds.sendEvent', (event) async {
+      _processSendEvent(event, chromeProxyService, dwdsStats);
+      return {'result': Success().toJson()};
+    });
+    await client.registerService('ext.dwds.sendEvent', 'DWDS');
+
     client.registerServiceCallback('ext.dwds.emitEvent', (event) async {
       emitEvent(DwdsEvent(
           event['type'] as String, event['payload'] as Map<String, dynamic>));
@@ -187,6 +194,28 @@ class DwdsVmClient {
   }
 }
 
+void _processSendEvent(Map<String, dynamic> event,
+    ChromeProxyService chromeProxyService, DwdsStats dwdsStats) {
+  var type = event['type'] as String;
+  var payload = event['payload'] as Map<String, dynamic>;
+  switch (type) {
+    case 'DevtoolsEvent':
+      {
+        var screen = payload == null ? null : payload['screen'];
+        var action = payload == null ? null : payload['action'];
+        if (screen == 'debugger' &&
+            action == 'screenReady' &&
+            dwdsStats.isFirstDebuggerReady()) {
+          emitEvent(DwdsEvent.debuggerReady(DateTime.now()
+              .difference(dwdsStats.debuggerStart)
+              .inMilliseconds));
+        } else {
+          _logger.warning('Ignoring unknown event: $event');
+        }
+      }
+  }
+}
+
 Future<void> _disableBreakpointsAndResume(
     VmService client, ChromeProxyService chromeProxyService) async {
   _logger.info('Attempting to disable breakpoints and resume the isolate');

dwds/lib/src/events.dart

@@ -6,12 +6,90 @@
 
 import 'dart:async';
 
+import 'package:vm_service/vm_service.dart';
+
+class DwdsStats {
+  /// The time when the user starts the debugger.
+  final DateTime debuggerStart;
+
+  var _isDebuggerReady = false;
+
+  /// Records and returns whether the debugger became ready.
+  bool isFirstDebuggerReady() {
+    final wasReady = _isDebuggerReady;
+    _isDebuggerReady = true;
+    return !wasReady;
+  }
+
+  DwdsStats(this.debuggerStart);
+}
+
+class DwdsEventKind {
+  static const String compilerUpdateDependencies =
+      'COMPILER_UPDATE_DEPENDENCIES';
+  static const String devtoolsLaunch = 'DEVTOOLS_LAUNCH';
+  static const String evaluate = 'EVALUATE';
+  static const String evaluateInFrame = 'EVALUATE_IN_FRAME';
+  static const String getIsolate = 'GET_ISOLATE';
+  static const String getScripts = 'GET_SCRIPTS';
+  static const String getSourceReport = 'GET_SOURCE_REPORT';
+  static const String debuggerReady = 'DEBUGGER_READY';
+  static const String getVM = 'GET_VM';
+  static const String resume = 'RESUME';
+
+  DwdsEventKind._();
+}
+
 class DwdsEvent {
   final String type;
   final Map<String, dynamic> payload;
 
   DwdsEvent(this.type, this.payload);
 
+  DwdsEvent.compilerUpdateDependencies(String entrypoint)
+      : this(DwdsEventKind.compilerUpdateDependencies, {
+          'entrypoint': entrypoint,
+        });
+
+  DwdsEvent.devtoolsLaunch() : this(DwdsEventKind.devtoolsLaunch, {});
+
+  DwdsEvent.evaluate(String expression, Response result)
+      : this(DwdsEventKind.evaluate, {
+          'expression': expression,
+          'success': result != null && result is InstanceRef,
+          if (result != null && result is ErrorRef) 'error': result,
+        });
+
+  DwdsEvent.evaluateInFrame(String expression, Response result)
+      : this(DwdsEventKind.evaluateInFrame, {
+          'expression': expression,
+          'success': result != null && result is InstanceRef,
+          if (result != null && result is ErrorRef) 'error': result,
+        });
+
+  DwdsEvent.getIsolate() : this(DwdsEventKind.getIsolate, {});
+
+  DwdsEvent.getScripts() : this(DwdsEventKind.getScripts, {});
+
+  DwdsEvent.getVM() : this(DwdsEventKind.getVM, {});
+
+  DwdsEvent.resume(String step) : this(DwdsEventKind.resume, {'step': step});
+
+  DwdsEvent.getSourceReport() : this(DwdsEventKind.getSourceReport, {});
+
+  DwdsEvent.debuggerReady(int elapsedMilliseconds)
+      : this(DwdsEventKind.debuggerReady, {
+          'elapsedMilliseconds': elapsedMilliseconds,
+        });
+
+  void addException(dynamic exception) {
+    payload['exception'] = exception;
+  }
+
+  void addElapsedTime(int elapsedMilliseconds) {
+    payload['elapsedMilliseconds'] = elapsedMilliseconds;
+  }
+
   @override
   String toString() {
     return 'TYPE: $type Payload: $payload';

dwds/lib/src/handlers/dev_handler.dart

@@ -222,12 +222,13 @@ class DevHandler {
   }
 
   Future<AppDebugServices> loadAppServices(AppConnection appConnection) async {
+    var dwdsStats = DwdsStats(DateTime.now());
     var appId = appConnection.request.appId;
     if (_servicesByAppId[appId] == null) {
       var debugService = await _startLocalDebugService(
           await _chromeConnection(), appConnection);
       var appServices = await _createAppDebugServices(
-          appConnection.request.appId, debugService);
+          appConnection.request.appId, debugService, dwdsStats);
       unawaited(appServices.chromeProxyService.remoteDebugger.onClose.first
           .whenComplete(() async {
         await appServices.close();
@@ -434,8 +435,8 @@ class DevHandler {
   }
 
   Future<AppDebugServices> _createAppDebugServices(
-      String appId, DebugService debugService) async {
-    var webdevClient = await DwdsVmClient.create(debugService);
+      String appId, DebugService debugService, DwdsStats dwdsStats) async {
+    var webdevClient = await DwdsVmClient.create(debugService, dwdsStats);
     if (_spawnDds) {
       await debugService.startDartDevelopmentService();
     }
@@ -463,6 +464,7 @@ class DevHandler {
     // Waits for a `DevToolsRequest` to be sent from the extension background
     // when the extension is clicked.
     extensionDebugger.devToolsRequestStream.listen((devToolsRequest) async {
+      var dwdsStats = DwdsStats(DateTime.now());
       var connection = _appConnectionByAppId[devToolsRequest.appId];
       if (connection == null) {
         // TODO(grouma) - Ideally we surface this warning to the extension so
@@ -491,8 +493,11 @@ class DevHandler {
           expressionCompiler: _expressionCompiler,
           spawnDds: _spawnDds,
         );
-        var appServices =
-            await _createAppDebugServices(devToolsRequest.appId, debugService);
+        var appServices = await _createAppDebugServices(
+          devToolsRequest.appId,
+          debugService,
+          dwdsStats,
+        );
         var encodedUri = await debugService.encodedUri;
         extensionDebugger.sendEvent('dwds.encodedUri', encodedUri);
         unawaited(appServices.chromeProxyService.remoteDebugger.onClose.first
@@ -516,7 +521,7 @@ class DevHandler {
     // TODO(grouma) - We may want to log the debugServiceUri if we don't launch
     // DevTools so that users can manually connect.
     if (!_serveDevTools) return;
-    emitEvent(DwdsEvent('DEVTOOLS_LAUNCH', {}));
+    emitEvent(DwdsEvent.devtoolsLaunch());
     await remoteDebugger.sendCommand('Target.createTarget', params: {
       'newWindow': true,
       'url': Uri(