login: Reject earlier (at get-server-settings) when server is too old

lib/model/server_support.dart

@@ -0,0 +1,65 @@
+import '../api/core.dart';
+import '../api/exception.dart';
+import '../api/model/initial_snapshot.dart';
+import '../api/route/realm.dart';
+import 'database.dart';
+
+/// The fields 'zulip_version', 'zulip_merge_base', and 'zulip_feature_level'
+/// from a /server_settings or /register response.
+class ZulipVersionData {
+  const ZulipVersionData({
+    required this.zulipVersion,
+    required this.zulipMergeBase,
+    required this.zulipFeatureLevel,
+  });
+
+  factory ZulipVersionData.fromServerSettings(GetServerSettingsResult serverSettings) =>
+    ZulipVersionData(
+      zulipVersion: serverSettings.zulipVersion,
+      zulipMergeBase: serverSettings.zulipMergeBase,
+      zulipFeatureLevel: serverSettings.zulipFeatureLevel);
+
+  factory ZulipVersionData.fromInitialSnapshot(InitialSnapshot initialSnapshot) =>
+    ZulipVersionData(
+      zulipVersion: initialSnapshot.zulipVersion,
+      zulipMergeBase: initialSnapshot.zulipMergeBase,
+      zulipFeatureLevel: initialSnapshot.zulipFeatureLevel);
+
+  /// Make a [ZulipVersionData] from a [MalformedServerResponseException],
+  /// if the body was readable/valid JSON and contained the data, else null.
+  ///
+  /// May be used for the /server_settings or the /register response.
+  ///
+  /// If there's a zulip_version but no zulip_feature_level,
+  /// we infer it's indeed a Zulip server,
+  /// just an ancient one before feature levels were introduced in Zulip 3.0,
+  /// and we set 0 for zulipFeatureLevel.
+  static ZulipVersionData? fromMalformedServerResponseException(MalformedServerResponseException e) {
+    try {
+      final data = e.data!;
+      return ZulipVersionData(
+        zulipVersion: data['zulip_version'] as String,
+        zulipMergeBase: data['zulip_merge_base'] as String?,
+        zulipFeatureLevel: data['zulip_feature_level'] as int? ?? 0);
+    } catch (inner) {
+      return null;
+    }
+  }
+
+  final String zulipVersion;
+  final String? zulipMergeBase;
+  final int zulipFeatureLevel;
+
+  bool matchesAccount(Account account) =>
+    zulipVersion == account.zulipVersion
+    && zulipMergeBase == account.zulipMergeBase
+    && zulipFeatureLevel == account.zulipFeatureLevel;
+
+  bool get isUnsupported => zulipFeatureLevel < kMinSupportedZulipFeatureLevel;
+}
+
+class ServerVersionUnsupportedException implements Exception {
+  final ZulipVersionData data;
+
+  ServerVersionUnsupportedException(this.data);
+}

lib/model/store.dart

@@ -28,6 +28,7 @@ import 'presence.dart';
 import 'realm.dart';
 import 'recent_dm_conversations.dart';
 import 'recent_senders.dart';
+import 'server_support.dart';
 import 'channel.dart';
 import 'saved_snippet.dart';
 import 'settings.dart';
@@ -208,7 +209,7 @@ abstract class GlobalStore extends ChangeNotifier {
       assert(account != null); // doLoadPerAccount would have thrown AccountNotFoundException
       final zulipLocalizations = GlobalLocalizations.zulipLocalizations;
       switch (e) {
-        case _ServerVersionUnsupportedException():
+        case ServerVersionUnsupportedException():
           reportErrorToUserModally(
             zulipLocalizations.errorCouldNotConnectTitle,
             message: zulipLocalizations.errorServerVersionUnsupportedMessage(
@@ -1026,9 +1027,9 @@ class UpdateMachine {
     try {
       initialSnapshot = await _registerQueueWithRetry(connection,
         stopAndThrowIfNoAccount: stopAndThrowIfNoAccount);
-    } on _ServerVersionUnsupportedException catch (e) {
+    } on ServerVersionUnsupportedException catch (e) {
       // `!` is OK because _registerQueueWithRetry would have thrown a
-      // not-_ServerVersionUnsupportedException if no account
+      // not-ServerVersionUnsupportedException if no account
       final account = globalStore.getAccount(accountId)!;
       if (!e.data.matchesAccount(account)) {
         await globalStore.updateZulipVersionData(accountId, e.data);
@@ -1094,7 +1095,7 @@ class UpdateMachine {
           case MalformedServerResponseException()
             when (zulipVersionData = ZulipVersionData.fromMalformedServerResponseException(e))
               ?.isUnsupported == true:
-            throw _ServerVersionUnsupportedException(zulipVersionData!);
+            throw ServerVersionUnsupportedException(zulipVersionData!);
           case HttpException(httpStatus: 401):
             // We cannot recover from this error through retrying.
             // Leave it to [GlobalStore.loadPerAccount].
@@ -1114,7 +1115,7 @@ class UpdateMachine {
         stopAndThrowIfNoAccount();
         final zulipVersionData = ZulipVersionData.fromInitialSnapshot(result);
         if (zulipVersionData.isUnsupported) {
-          throw _ServerVersionUnsupportedException(zulipVersionData);
+          throw ServerVersionUnsupportedException(zulipVersionData);
         }
         return result;
       }
@@ -1529,58 +1530,6 @@ class UpdateMachine {
   String toString() => '${objectRuntimeType(this, 'UpdateMachine')}#${shortHash(this)}';
 }
 
-/// The fields 'zulip_version', 'zulip_merge_base', and 'zulip_feature_level'
-/// from a /register response.
-class ZulipVersionData {
-  const ZulipVersionData({
-    required this.zulipVersion,
-    required this.zulipMergeBase,
-    required this.zulipFeatureLevel,
-  });
-
-  factory ZulipVersionData.fromInitialSnapshot(InitialSnapshot initialSnapshot) =>
-    ZulipVersionData(
-      zulipVersion: initialSnapshot.zulipVersion,
-      zulipMergeBase: initialSnapshot.zulipMergeBase,
-      zulipFeatureLevel: initialSnapshot.zulipFeatureLevel);
-
-  /// Make a [ZulipVersionData] from a [MalformedServerResponseException],
-  /// if the body was readable/valid JSON and contained the data, else null.
-  ///
-  /// If there's a zulip_version but no zulip_feature_level,
-  /// we infer it's indeed a Zulip server,
-  /// just an ancient one before feature levels were introduced in Zulip 3.0,
-  /// and we set 0 for zulipFeatureLevel.
-  static ZulipVersionData? fromMalformedServerResponseException(MalformedServerResponseException e) {
-    try {
-      final data = e.data!;
-      return ZulipVersionData(
-        zulipVersion: data['zulip_version'] as String,
-        zulipMergeBase: data['zulip_merge_base'] as String?,
-        zulipFeatureLevel: data['zulip_feature_level'] as int? ?? 0);
-    } catch (inner) {
-      return null;
-    }
-  }
-
-  final String zulipVersion;
-  final String? zulipMergeBase;
-  final int zulipFeatureLevel;
-
-  bool matchesAccount(Account account) =>
-    zulipVersion == account.zulipVersion
-    && zulipMergeBase == account.zulipMergeBase
-    && zulipFeatureLevel == account.zulipFeatureLevel;
-
-  bool get isUnsupported => zulipFeatureLevel < kMinSupportedZulipFeatureLevel;
-}
-
-class _ServerVersionUnsupportedException implements Exception {
-  final ZulipVersionData data;
-
-  _ServerVersionUnsupportedException(this.data);
-}
-
 class _EventHandlingException implements Exception {
   final Object cause;
   final Event event;

lib/widgets/login.dart

@@ -5,6 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:url_launcher/url_launcher.dart';
 
+import '../api/core.dart';
 import '../api/exception.dart';
 import '../api/model/web_auth.dart';
 import '../api/route/account.dart';
@@ -13,6 +14,7 @@ import '../api/route/users.dart';
 import '../generated/l10n/zulip_localizations.dart';
 import '../log.dart';
 import '../model/binding.dart';
+import '../model/server_support.dart';
 import '../model/store.dart';
 import 'dialog.dart';
 import 'home.dart';
@@ -180,25 +182,43 @@ class _AddAccountPageState extends State<AddAccountPage> {
         final connection = globalStore.apiConnection(realmUrl: url!, zulipFeatureLevel: null);
         try {
           serverSettings = await getServerSettings(connection);
+          final zulipVersionData = ZulipVersionData.fromServerSettings(serverSettings);
+          if (zulipVersionData.isUnsupported) {
+            throw ServerVersionUnsupportedException(zulipVersionData);
+          }
+        } on MalformedServerResponseException catch (e) {
+          final zulipVersionData = ZulipVersionData.fromMalformedServerResponseException(e);
+          if (zulipVersionData != null && zulipVersionData.isUnsupported) {
+            throw ServerVersionUnsupportedException(zulipVersionData);
+          }
+          rethrow;
         } finally {
           connection.close();
         }
       } catch (e) {
-        if (!context.mounted) {
-          return;
+        if (!context.mounted) return;
+
+        String? message;
+        Uri? learnMoreButtonUrl;
+        switch (e) {
+          case ServerVersionUnsupportedException(:final data):
+            message = zulipLocalizations.errorServerVersionUnsupportedMessage(
+              url.toString(),
+              data.zulipVersion,
+              kMinSupportedZulipVersion);
+            learnMoreButtonUrl = kServerSupportDocUrl;
+          default:
+            // TODO(#105) give more helpful feedback; see `fetchServerSettings`
+            //   in zulip-mobile's src/message/fetchActions.js.
+            message = zulipLocalizations.errorLoginCouldNotConnect(url.toString());
         }
-        // TODO(#105) give more helpful feedback; see `fetchServerSettings`
-        //   in zulip-mobile's src/message/fetchActions.js.
         showErrorDialog(context: context,
           title: zulipLocalizations.errorCouldNotConnectTitle,
-          message: zulipLocalizations.errorLoginCouldNotConnect(url.toString()));
-        return;
-      }
-      // https://github.com/dart-lang/linter/issues/4007
-      // ignore: use_build_context_synchronously
-      if (!context.mounted) {
+          message: message,
+          learnMoreButtonUrl: learnMoreButtonUrl);
         return;
       }
+      if (!context.mounted) return;
 
       unawaited(Navigator.push(context,
         LoginPage.buildRoute(serverSettings: serverSettings)));

test/api/route/route_checks.dart

@@ -1,12 +1,18 @@
 import 'package:checks/checks.dart';
 import 'package:zulip/api/route/messages.dart';
+import 'package:zulip/api/route/realm.dart';
 import 'package:zulip/api/route/saved_snippets.dart';
 
 extension SendMessageResultChecks on Subject<SendMessageResult> {
   Subject<int> get id => has((e) => e.id, 'id');
 }
+
 extension CreateSavedSnippetResultChecks on Subject<CreateSavedSnippetResult> {
   Subject<int> get savedSnippetId => has((e) => e.savedSnippetId, 'savedSnippetId');
 }
 
+extension GetServerSettingsResultChecks on Subject<GetServerSettingsResult> {
+  Subject<Uri> get realmUrl => has((e) => e.realmUrl, 'realmUrl');
+}
+
 // TODO add similar extensions for other classes in api/route/*.dart

test/model/store_checks.dart

@@ -6,6 +6,7 @@ import 'package:zulip/model/autocomplete.dart';
 import 'package:zulip/model/binding.dart';
 import 'package:zulip/model/database.dart';
 import 'package:zulip/model/recent_dm_conversations.dart';
+import 'package:zulip/model/server_support.dart';
 import 'package:zulip/model/settings.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/model/unreads.dart';

test/model/store_test.dart

@@ -17,6 +17,7 @@ import 'package:zulip/api/route/realm.dart';
 import 'package:zulip/log.dart';
 import 'package:zulip/model/actions.dart';
 import 'package:zulip/model/presence.dart';
+import 'package:zulip/model/server_support.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/notifications/receive.dart';
 

test/widgets/checks.dart

@@ -1,5 +1,6 @@
 import 'package:checks/checks.dart';
 import 'package:flutter/widgets.dart';
+import 'package:zulip/api/route/realm.dart';
 
 import 'package:zulip/model/emoji.dart';
 import 'package:zulip/model/narrow.dart';
@@ -8,6 +9,7 @@ import 'package:zulip/widgets/compose_box.dart';
 import 'package:zulip/widgets/content.dart';
 import 'package:zulip/widgets/emoji.dart';
 import 'package:zulip/widgets/emoji_reaction.dart';
+import 'package:zulip/widgets/login.dart';
 import 'package:zulip/widgets/message_list.dart';
 import 'package:zulip/widgets/page.dart';
 import 'package:zulip/widgets/profile.dart';
@@ -74,6 +76,10 @@ extension AccountRouteChecks<T> on Subject<AccountRoute<T>> {
   Subject<int> get accountId => has((x) => x.accountId, 'accountId');
 }
 
+extension LoginPageChecks on Subject<LoginPage> {
+  Subject<GetServerSettingsResult> get serverSettings => has((x) => x.serverSettings, 'serverSettings');
+}
+
 extension ProfilePageChecks on Subject<ProfilePage> {
   Subject<int> get userId => has((x) => x.userId, 'userId');
 }

test/widgets/dialog_test.dart

@@ -7,7 +7,6 @@ import 'package:url_launcher/url_launcher.dart';
 import 'package:zulip/model/settings.dart';
 import 'package:zulip/widgets/app.dart';
 import 'package:zulip/widgets/dialog.dart';
-import 'package:zulip/widgets/store.dart';
 
 import '../model/binding.dart';
 import 'dialog_checks.dart';