log: Return Future from reportErrorToUserBriefly.

Similar to the refactor in commit ece8f72 to `showErrorDialog`,
returning `Future` here allows the caller to know when the `SnackBar`
is closed.

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

Author: PIG208

lib/log.dart

@@ -31,7 +31,7 @@ bool debugLog(String message) {
   return true;
 }
 
-typedef ReportErrorCallback = void Function(String? message, {String? details});
+typedef ReportErrorCallback = Future<void> Function(String? message, {String? details});
 
 /// Display an error message in a [SnackBar].
 ///
@@ -43,12 +43,15 @@ typedef ReportErrorCallback = void Function(String? message, {String? details});
 ///
 /// If `details` is non-null, the [SnackBar] will contain a button that would
 /// open a dialog containing the error details.
+///
+/// Returns a [Future] that resolves when the [SnackBar] is no longer visible.
+/// If [ZulipApp] is not ready, the [Future] resolves immediately.
 // This gets set in [ZulipApp].  We need this indirection to keep `lib/log.dart`
 // from importing widget code, because the file is a dependency for the rest of
 // the app.
 ReportErrorCallback reportErrorToUserBriefly = defaultReportErrorToUserBriefly;
 
-void defaultReportErrorToUserBriefly(String? message, {String? details}) {
+Future<void> defaultReportErrorToUserBriefly(String? message, {String? details}) async {
   // Error dismissing is a no-op to the default handler.
   if (message == null) return;
   // If this callback is still in place, then the app's widget tree

lib/widgets/app.dart

@@ -98,7 +98,7 @@ class ZulipApp extends StatefulWidget {
 
   static int _snackBarCount = 0;
 
-  static void _reportErrorToUserBriefly(String? message, {String? details}) {
+  static Future<void> _reportErrorToUserBriefly(String? message, {String? details}) async {
     assert(_ready.value);
 
     if (message == null) {
@@ -129,7 +129,8 @@ class ZulipApp extends StatefulWidget {
                 message: details))));
 
     _snackBarCount++;
-    newSnackBar.closed.whenComplete(() => _snackBarCount--);
+    await newSnackBar.closed;
+    _snackBarCount--;
   }
 
   void _declareReady() {