fix(imap): fail pending commands when the connection is lost

lib/src/imap/imap_client.dart

@@ -335,9 +335,37 @@ class ImapClient extends ClientBase {
     _isInIdleMode = false;
     _selectedMailbox = null;
     _failPendingIdleContinuation('connection error: $error');
+    // Previously only the event below was fired, so a command that was
+    // awaiting a response when the socket died never completed: with no
+    // responseTimeout set, `await sendCommand(...)` hung for the lifetime of
+    // the process, and even with one it waited out the full timeout for an
+    // error that had already arrived. The event cannot complete the caller's
+    // future on its own.
+    _completePendingTasksWithError(error);
     fireEvent(ImapConnectionLostEvent(this));
   }
 
+  /// Error-completes every task that is queued or awaiting a response.
+  void _completePendingTasksWithError(dynamic error) {
+    final pending = <CommandTask>[..._queue, ..._tasks.values];
+    _queue.clear();
+    _tasks.clear();
+    _currentCommandTask = null;
+    _idleCommandTask = null;
+    for (final task in pending) {
+      if (task.completer.isCompleted) {
+        continue;
+      }
+      try {
+        task.completer.completeError(
+          ImapException(this, 'connection lost: $error'),
+        );
+      } catch (e) {
+        logApp('unable to completeError for task $task: $e');
+      }
+    }
+  }
+
   @override
   Future<void> disconnect() async {
     // Fail-first so any future returned by idleStart(waitForContinuation:true)

test/imap/imap_client_test.dart

@@ -2,7 +2,7 @@
 // cSpell:disable
 
 import 'dart:async';
-import 'dart:io' show Platform;
+import 'dart:io' show Platform, SocketException;
 
 import 'package:enough_mail/enough_mail.dart';
 import 'package:enough_mail/src/private/util/client_base.dart';
@@ -1440,6 +1440,47 @@ void main() {
     expect(uidResponseCode?.targetSequence.toList().first, 176);
   });
 
+  test(
+    'ImapClient fails commands awaiting a response when the connection is lost',
+    () async {
+      await _selectInbox();
+      // No server response is configured, so this NOOP stays in flight.
+      mockServer.response = null;
+      final pending = client.noop();
+      await Future.delayed(const Duration(milliseconds: 15));
+
+      client.onConnectionError(const SocketException('connection reset'));
+
+      await expectLater(
+        pending,
+        throwsA(
+          isA<ImapException>().having(
+            (e) => e.message,
+            'message',
+            contains('connection lost'),
+          ),
+        ),
+      );
+    },
+  );
+
+  test(
+    'ImapClient fails queued commands when the connection is lost',
+    () async {
+      await _selectInbox();
+      mockServer.response = null;
+      // The first command is sent and waits; the second is queued behind it.
+      final inFlight = client.noop();
+      final queued = client.noop();
+      await Future.delayed(const Duration(milliseconds: 15));
+
+      client.onConnectionError(const SocketException('connection reset'));
+
+      await expectLater(inFlight, throwsA(isA<ImapException>()));
+      await expectLater(queued, throwsA(isA<ImapException>()));
+    },
+  );
+
   test('ImapClient idle', () async {
     final box = await _selectInbox();
     expungedMessages = [];