[analysis_server] Record unhandled exceptions in message handler zone

This `socketError` callback doesn't record exceptions to the instrumentation service because they were expected to be things like the socket closing. However it was also used for unhandled errors in the zone used for handling errors, which meant they also were not logged. This meant the user would see the error text, but the stack trace would never be logged anyway.

With this change, unhandled exceptions from the zone will be logged through the instrumentation service too.

Fixes #62082

Change-Id: I71d56a8b3c9241744eb614d74de46c190d61f2e3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/464381
Commit-Queue: Keerti Parthasarathy <keertip@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Keerti Parthasarathy <keertip@google.com>

Author: DanTup

pkg/analysis_server/lib/src/lsp/lsp_analysis_server.dart

@@ -559,7 +559,7 @@ class LspAnalysisServer extends AnalysisServer {
         logException(errorMessage, error, stackTrace);
         completer?.setComplete();
       }
-    }, socketError);
+    }, unhandledZoneError);
   }
 
   /// Logs the error on the client using window/logMessage.
@@ -991,10 +991,22 @@ class LspAnalysisServer extends AnalysisServer {
   /// There was an error related to the socket from which messages are being
   /// read.
   void socketError(Object error, StackTrace? stackTrace) {
-    // Don't send to instrumentation service; not an internal error.
+    // Don't send to instrumentation service; not an internal error. Probably
+    // caused by server shutdown or similar.
     sendServerErrorNotification('Socket error', error, stackTrace);
   }
 
+  /// There was an unhandled async error in the zone used to execute the
+  /// message handler.
+  void unhandledZoneError(Object error, StackTrace? stackTrace) {
+    // Record to the instrumentation log so the stack trace is accessible. This
+    // is an unhandled exception that was not awaited and is almost certainly a
+    // bug.
+    instrumentationService.logException(error, stackTrace);
+
+    sendServerErrorNotification('Unhandled handler error', error, stackTrace);
+  }
+
   /// Updates the active set of workspace folders.
   ///
   /// This is provided by the client at startup and may be updated by