store: Show error message when replacing event queue.

Fixes: zulip#555

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

assets/l10n/app_en.arb

@@ -180,6 +180,11 @@
       "error": {"type": "String", "example": "Network request failed: HTTP status 500"}
     }
   },
+  "errorReconnectingToServer": "Reconnecting to server at {url}...",
+  "@errorReconnectingToServer": {
+    "url": {"type": "String", "example": "http://example.com/"},
+    "description": "Message when reconnecting to the server."
+  },
   "errorSharingFailed": "Sharing failed",
   "@errorSharingFailed": {
     "description": "Error message when sharing a message failed."

lib/model/store.dart

@@ -789,6 +789,8 @@ class UpdateMachine {
         switch (e) {
           case ZulipApiException(code: 'BAD_EVENT_QUEUE_ID'):
             assert(debugLog('Lost event queue for $store.  Replacing…'));
+            reportErrorToUserInSnackBar(localizations.errorReconnectingToServer(
+              store.connection.realmUrl.origin));
             await store._globalStore._reloadPerAccount(store.accountId);
             dispose();
             debugLog('… Event queue replaced.');

test/model/store_test.dart

@@ -406,7 +406,10 @@ void main() {
       });
       updateMachine.debugAdvanceLoop();
       async.flushMicrotasks();
+      check(debugLastReportedError).isNull();
       await Future<void>.delayed(Duration.zero);
+      check(debugTakeLastReportedError()).isNotNull()
+        .contains('Reconnecting to server at ${eg.realmUrl.origin}...');
       check(store).isLoading.isTrue();
 
       // The global store has a new store.