Fix crash on processing devtools event

analysis_options.yaml

@@ -1,6 +1,4 @@
 analyzer:
-  strong-mode:
-    implicit-casts: false
   errors:
     dead_code: error
     unused_element: error

dwds/CHANGELOG.md

@@ -14,6 +14,8 @@
 - Pre-warm expression compiler cache to speed up Flutter Inspector loading.
 - Remove `ChromeProxyService.setExceptionPauseMode()`.
 - Display full error on failure to start DDS.
+- Fix crash on processing DevTools event when starting DevTools from observatory
+  uri.
 
 ## 16.0.1
 

dwds/lib/src/dwds_vm_client.dart

@@ -152,18 +152,22 @@ void _processSendEvent(Map<String, dynamic> event,
         _logger.finest('Received DevTools event: $event');
         final action = payload?['action'] as String?;
         final screen = payload?['screen'] as String?;
+        final devToolsStart = dwdsStats.devToolsStart;
+        final debuggerStart = dwdsStats.debuggerStart;
         if (screen != null && action == 'pageReady') {
           if (dwdsStats.isFirstDebuggerReady) {
-            final debuggerReadyTime = DateTime.now()
-                .difference(dwdsStats.devToolsStart)
-                .inMilliseconds;
-            emitEvent(DwdsEvent.devToolsLoad(debuggerReadyTime, screen));
-            _logger.fine('DevTools load time: $debuggerReadyTime ms');
-            final debuggerStartTime = DateTime.now()
-                .difference(dwdsStats.debuggerStart)
-                .inMilliseconds;
-            emitEvent(DwdsEvent.debuggerReady(debuggerStartTime, screen));
-            _logger.fine('Debugger ready time: $debuggerStartTime ms');
+            if (devToolsStart != null) {
+              final debuggerReadyTime =
+                  DateTime.now().difference(devToolsStart).inMilliseconds;
+              emitEvent(DwdsEvent.devToolsLoad(debuggerReadyTime, screen));
+              _logger.fine('DevTools load time: $debuggerReadyTime ms');
+            }
+            if (debuggerStart != null) {
+              final debuggerStartTime =
+                  DateTime.now().difference(debuggerStart).inMilliseconds;
+              emitEvent(DwdsEvent.debuggerReady(debuggerStartTime, screen));
+              _logger.fine('Debugger ready time: $debuggerStartTime ms');
+            }
           } else {
             _logger
                 .finest('Debugger and DevTools startup times already recorded.'

dwds/lib/src/events.dart

@@ -8,12 +8,12 @@ import 'package:vm_service/vm_service.dart';
 
 class DwdsStats {
   /// The time when the user starts the debugger.
-  late DateTime _debuggerStart;
-  DateTime get debuggerStart => _debuggerStart;
+  DateTime? _debuggerStart;
+  DateTime? get debuggerStart => _debuggerStart;
 
   /// The time when dwds launches DevTools.
-  late DateTime _devToolsStart;
-  DateTime get devToolsStart => _devToolsStart;
+  DateTime? _devToolsStart;
+  DateTime? get devToolsStart => _devToolsStart;
 
   /// Records and returns weither the debugger is ready.
   bool _isFirstDebuggerReady = true;