user [nfc]: Factor out a getUser method

Author: gnprice

lib/model/compose.dart

@@ -190,7 +190,7 @@ String quoteAndReplyPlaceholder(
   PerAccountStore store, {
   required Message message,
 }) {
-  final sender = store.users[message.senderId];
+  final sender = store.getUser(message.senderId);
   assert(sender != null); // TODO(#716): should use `store.senderDisplayName`
   final url = narrowLink(store,
     SendableNarrow.ofMessage(message, selfUserId: store.selfUserId),
@@ -212,7 +212,7 @@ String quoteAndReply(PerAccountStore store, {
   required Message message,
   required String rawContent,
 }) {
-  final sender = store.users[message.senderId];
+  final sender = store.getUser(message.senderId);
   assert(sender != null); // TODO(#716): should use `store.senderDisplayName`
   final url = narrowLink(store,
     SendableNarrow.ofMessage(message, selfUserId: store.selfUserId),

lib/model/user.dart

@@ -37,7 +37,14 @@ mixin UserStore {
   /// i.e. the account the person using this app is logged into.
   ///
   /// When only the user ID is needed, see [selfUserId].
-  User get selfUser => users[selfUserId]!;
+  User get selfUser => getUser(selfUserId)!;
+
+  /// The user with the given ID, if that user is known.
+  ///
+  /// There may be perfectly real users that are not known,
+  /// so callers must handle that possibility.
+  /// For details, see [users].
+  User? getUser(int userId) => users[userId];
 
   /// The name to show the given user as in the UI, even for unknown users.
   ///
@@ -47,7 +54,7 @@ mixin UserStore {
   /// When a [Message] is available which the user sent,
   /// use [senderDisplayName] instead for a better-informed fallback.
   String userDisplayName(int userId) {
-    return users[userId]?.fullName
+    return getUser(userId)?.fullName
       ?? GlobalLocalizations.zulipLocalizations.unknownUserName;
   }
 
@@ -60,7 +67,7 @@ mixin UserStore {
   /// For a user who isn't the sender of some known message,
   /// see [userDisplayName].
   String senderDisplayName(Message message) {
-    return users[message.senderId]?.fullName
+    return getUser(message.senderId)?.fullName
       ?? message.senderFullName;
   }
 }

lib/widgets/autocomplete.dart

@@ -200,7 +200,7 @@ class ComposeAutocomplete extends AutocompleteField<ComposeAutocompleteQuery, Co
         if (query is! MentionAutocompleteQuery) {
           return; // Shrug; similar to `intent == null` case above.
         }
-        final user = store.users[userId]!; // must exist because UserMentionAutocompleteResult
+        final user = store.getUser(userId)!; // must exist because UserMentionAutocompleteResult
         // TODO(i18n) language-appropriate space character; check active keyboard?
         //   (maybe handle centrally in `controller`)
         replacementString = '${userMention(user, silent: query.silent, users: store)} ';
@@ -268,7 +268,7 @@ class _MentionAutocompleteItem extends StatelessWidget {
     Widget label;
     switch (option) {
       case UserMentionAutocompleteResult(:var userId):
-        final user = store.users[userId]!; // must exist because UserMentionAutocompleteResult
+        final user = store.getUser(userId)!; // must exist because UserMentionAutocompleteResult
         avatar = Avatar(userId: userId, size: 32, borderRadius: 3); // web uses 21px
         label = Text(user.fullName);
       case WildcardMentionAutocompleteResult(:var wildcardOption):

lib/widgets/compose_box.dart

@@ -664,7 +664,7 @@ class _FixedDestinationContentInput extends StatelessWidget {
 
       case DmNarrow(otherRecipientIds: [final otherUserId]):
         final store = PerAccountStoreWidget.of(context);
-        final fullName = store.users[otherUserId]?.fullName;
+        final fullName = store.getUser(otherUserId)?.fullName;
         if (fullName == null) return zulipLocalizations.composeBoxGenericContentHint;
         return zulipLocalizations.composeBoxDmContentHint(fullName);
 
@@ -1431,7 +1431,7 @@ class _ComposeBoxState extends State<ComposeBox> with PerAccountStoreAwareStateM
 
       case DmNarrow(:final otherRecipientIds):
         final hasDeactivatedUser = otherRecipientIds.any((id) =>
-          !(store.users[id]?.isActive ?? true));
+          !(store.getUser(id)?.isActive ?? true));
         if (hasDeactivatedUser) {
           return _ErrorBanner(label:
             ZulipLocalizations.of(context).errorBannerDeactivatedDmLabel);

lib/widgets/content.dart

@@ -1509,7 +1509,7 @@ class AvatarImage extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final store = PerAccountStoreWidget.of(context);
-    final user = store.users[userId];
+    final user = store.getUser(userId);
 
     if (user == null) { // TODO(log)
       return const SizedBox.shrink();

lib/widgets/message_list.dart

@@ -1330,7 +1330,7 @@ class MessageWithPossibleSender extends StatelessWidget {
     final designVariables = DesignVariables.of(context);
 
     final message = item.message;
-    final sender = store.users[message.senderId];
+    final sender = store.getUser(message.senderId);
 
     Widget? senderRow;
     if (item.showSender) {

lib/widgets/profile.dart

@@ -67,7 +67,7 @@ class ProfilePage extends StatelessWidget {
   Widget build(BuildContext context) {
     final zulipLocalizations = ZulipLocalizations.of(context);
     final store = PerAccountStoreWidget.of(context);
-    final user = store.users[userId];
+    final user = store.getUser(userId);
     if (user == null) {
       return const _ProfileErrorPage();
     }

test/model/user_test.dart

@@ -60,7 +60,7 @@ void main() {
       final store = eg.store(initialSnapshot: eg.initialSnapshot(
         realmUsers: [eg.selfUser, user]));
 
-      User getUser() => store.users[user.userId]!;
+      User getUser() => store.getUser(user.userId)!;
 
       await store.handleEvent(RealmUserUpdateEvent(id: 1, userId: user.userId,
         deliveryEmail: null));