Comprehensively retry event-poll failures

assets/l10n/app_en.arb

@@ -188,6 +188,19 @@
       "error": {"type": "String", "example": "Invalid format"}
     }
   },
+  "errorHandlingEventTitle": "Error handling a Zulip event. Retrying connection…",
+  "@errorHandlingEventTitle": {
+    "description": "Error title on failing to handle a Zulip server event."
+  },
+  "errorHandlingEventDetails": "Error handling a Zulip event from {serverUrl}; will retry.\n\nError: {error}\n\nEvent: {event}",
+  "@errorHandlingEventDetails": {
+    "description": "Error details on failing to handle a Zulip server event.",
+    "placeholders": {
+      "serverUrl": {"type":  "String", "example":  "https://chat.example.com"},
+      "error": {"type": "String", "example": "Unexpected null value"},
+      "event": {"type": "String", "example": "UpdateMessageEvent(id: 123, messageIds: [2345, 3456], newTopic: 'dinner')"}
+    }
+  },
   "errorSharingFailed": "Sharing failed",
   "@errorSharingFailed": {
     "description": "Error message when sharing a message failed."

lib/api/exception.dart

@@ -91,7 +91,7 @@ class NetworkException extends ApiRequestException {
 /// This should always represent either some kind of operational issue
 /// on the server, or a bug in the server where its responses don't
 /// agree with the documented API.
-abstract class ServerException extends ApiRequestException {
+sealed class ServerException extends ApiRequestException {
   final int httpStatus;
 
   /// The response body, decoded as a JSON object.

lib/api/model/events.dart

@@ -215,6 +215,7 @@ sealed class RealmUserEvent extends Event {
 @JsonSerializable(fieldRename: FieldRename.snake)
 class RealmUserAddEvent extends RealmUserEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'add';
 
   final User person;
@@ -231,6 +232,7 @@ class RealmUserAddEvent extends RealmUserEvent {
 /// A [RealmUserEvent] with op `remove`: https://zulip.com/api/get-events#realm_user-remove
 class RealmUserRemoveEvent extends RealmUserEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'remove';
 
   final int userId;
@@ -268,6 +270,7 @@ class RealmUserUpdateCustomProfileField {
 @JsonSerializable(fieldRename: FieldRename.snake)
 class RealmUserUpdateEvent extends RealmUserEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'update';
 
   @JsonKey(readValue: _readFromPerson) final int userId;
@@ -351,6 +354,7 @@ sealed class ChannelEvent extends Event {
 @JsonSerializable(fieldRename: FieldRename.snake)
 class ChannelCreateEvent extends ChannelEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'create';
 
   final List<ZulipStream> streams;
@@ -368,6 +372,7 @@ class ChannelCreateEvent extends ChannelEvent {
 @JsonSerializable(fieldRename: FieldRename.snake)
 class ChannelDeleteEvent extends ChannelEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'delete';
 
   final List<ZulipStream> streams;
@@ -385,6 +390,7 @@ class ChannelDeleteEvent extends ChannelEvent {
 @JsonSerializable(fieldRename: FieldRename.snake)
 class ChannelUpdateEvent extends ChannelEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'update';
 
   final int streamId;
@@ -666,6 +672,7 @@ class UserTopicEvent extends Event {
 //   in order to skip the boilerplate in [fromJson] and [toJson].
 class MessageEvent extends Event {
   @override
+  @JsonKey(includeToJson: true)
   String get type => 'message';
 
   // In the server API, the `flags` field appears directly on the event rather
@@ -857,6 +864,7 @@ sealed class UpdateMessageFlagsEvent extends Event {
 @JsonSerializable(fieldRename: FieldRename.snake)
 class UpdateMessageFlagsAddEvent extends UpdateMessageFlagsEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'add';
 
   final bool all;
@@ -879,6 +887,7 @@ class UpdateMessageFlagsAddEvent extends UpdateMessageFlagsEvent {
 @JsonSerializable(fieldRename: FieldRename.snake)
 class UpdateMessageFlagsRemoveEvent extends UpdateMessageFlagsEvent {
   @override
+  @JsonKey(includeToJson: true)
   String get op => 'remove';
 
   // final bool all; // deprecated, ignore

lib/generated/l10n/zulip_localizations.dart

@@ -343,6 +343,18 @@ abstract class ZulipLocalizations {
   /// **'Error connecting to Zulip at {serverUrl}. Will retry:\n\n{error}'**
   String errorConnectingToServerDetails(String serverUrl, String error);
 
+  /// Error title on failing to handle a Zulip server event.
+  ///
+  /// In en, this message translates to:
+  /// **'Error handling a Zulip event. Retrying connection…'**
+  String get errorHandlingEventTitle;
+
+  /// Error details on failing to handle a Zulip server event.
+  ///
+  /// In en, this message translates to:
+  /// **'Error handling a Zulip event from {serverUrl}; will retry.\n\nError: {error}\n\nEvent: {event}'**
+  String errorHandlingEventDetails(String serverUrl, String error, String event);
+
   /// Error message when sharing a message failed.
   ///
   /// In en, this message translates to:

lib/generated/l10n/zulip_localizations_ar.dart

@@ -157,6 +157,14 @@ class ZulipLocalizationsAr extends ZulipLocalizations {
     return 'Error connecting to Zulip at $serverUrl. Will retry:\n\n$error';
   }
 
+  @override
+  String get errorHandlingEventTitle => 'Error handling a Zulip event. Retrying connection…';
+
+  @override
+  String errorHandlingEventDetails(String serverUrl, String error, String event) {
+    return 'Error handling a Zulip event from $serverUrl; will retry.\n\nError: $error\n\nEvent: $event';
+  }
+
   @override
   String get errorSharingFailed => 'Sharing failed';
 

lib/generated/l10n/zulip_localizations_en.dart

@@ -157,6 +157,14 @@ class ZulipLocalizationsEn extends ZulipLocalizations {
     return 'Error connecting to Zulip at $serverUrl. Will retry:\n\n$error';
   }
 
+  @override
+  String get errorHandlingEventTitle => 'Error handling a Zulip event. Retrying connection…';
+
+  @override
+  String errorHandlingEventDetails(String serverUrl, String error, String event) {
+    return 'Error handling a Zulip event from $serverUrl; will retry.\n\nError: $error\n\nEvent: $event';
+  }
+
   @override
   String get errorSharingFailed => 'Sharing failed';
 

lib/generated/l10n/zulip_localizations_ja.dart

@@ -157,6 +157,14 @@ class ZulipLocalizationsJa extends ZulipLocalizations {
     return 'Error connecting to Zulip at $serverUrl. Will retry:\n\n$error';
   }
 
+  @override
+  String get errorHandlingEventTitle => 'Error handling a Zulip event. Retrying connection…';
+
+  @override
+  String errorHandlingEventDetails(String serverUrl, String error, String event) {
+    return 'Error handling a Zulip event from $serverUrl; will retry.\n\nError: $error\n\nEvent: $event';
+  }
+
   @override
   String get errorSharingFailed => 'Sharing failed';