new-dm: Exclude deactivated users

Fixes #1743.

Author: gnprice

lib/widgets/new_dm_sheet.dart

@@ -1,4 +1,3 @@
-import 'package:collection/collection.dart';
 import 'package:flutter/material.dart';
 import '../api/model/model.dart';
 import '../generated/l10n/zulip_localizations.dart';
@@ -69,9 +68,9 @@ class _NewDmPickerState extends State<NewDmPicker> with PerAccountStoreAwareStat
   }
 
   void _initSortedUsers(PerAccountStore store) {
-    final sansMuted = store.allUsers
-      .whereNot((user) => store.isUserMuted(user.userId));
-    sortedUsers = List<User>.from(sansMuted)
+    final users = store.allUsers
+      .where((user) => user.isActive && !store.isUserMuted(user.userId));
+    sortedUsers = List<User>.from(users)
       ..sort((a, b) => MentionAutocompleteView.compareByDms(a, b, store: store));
     _updateFilteredUsers(store);
   }

test/widgets/new_dm_sheet_test.dart

@@ -140,6 +140,22 @@ void main() {
       check(findText(includePlaceholders: false, 'Bob Brown')).findsNothing();
     });
 
+    testWidgets('deactivated users excluded', (tester) async {
+      // Omit a deactivated user both before there's a query…
+      final deactivatedUser = eg.user(fullName: 'Impostor Charlie', isActive: false);
+      await setupSheet(tester, users: [...testUsers, deactivatedUser]);
+      check(findText(includePlaceholders: false, 'Impostor Charlie')).findsNothing();
+      check(findText(includePlaceholders: false, 'Charlie Carter')).findsOne();
+      check(find.byIcon(ZulipIcons.check_circle_unchecked)).findsExactly(3);
+
+      // … and after a query that would match their name.
+      await tester.enterText(find.byType(TextField), 'Charlie');
+      await tester.pump();
+      check(findText(includePlaceholders: false, 'Impostor Charlie')).findsNothing();
+      check(findText(includePlaceholders: false, 'Charlie Carter')).findsOne();
+      check(find.byIcon(ZulipIcons.check_circle_unchecked)).findsExactly(1);
+    });
+
     testWidgets('muted users excluded', (tester) async {
       // Omit muted users both before there's a query…
       final mutedUser = eg.user(fullName: 'Someone Muted');