profile: Display user email

Fixes: zulip#291

lib/widgets/profile.dart

@@ -3,9 +3,11 @@ import 'dart:convert';
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 
+import '../api/model/initial_snapshot.dart';
 import '../api/model/model.dart';
 import '../model/content.dart';
 import '../model/narrow.dart';
+import '../model/store.dart';
 import 'content.dart';
 import 'message_list.dart';
 import 'page.dart';
@@ -33,6 +35,37 @@ class ProfilePage extends StatelessWidget {
       page: ProfilePage(userId: userId));
   }
 
+  /// The given user's real email address, if known, for displaying in the UI.
+  ///
+  /// Returns null if self-user isn't able to see [user]'s real email address.
+  ///
+  /// **Note:** Starting from Zulip version 7.0 (FL 163), there's a change in
+  /// the API about how self-user can access [user]'s real email address.
+  /// Search for "delivery_email" in https://zulip.com/api/register-queue.
+  // TODO(server-7, FL >= 163): remove
+  String? _getDisplayEmailFor(User user, {required PerAccountStore store}) {
+    if (store.account.zulipFeatureLevel >= 163) {
+      // A non-null value means [selfUser] has access to [user]'s real email,
+      // while a null value means it doesn't have access to the email.
+      return user.deliveryEmail;
+    } else {
+      if (user.deliveryEmail != null) {
+        // A non-null value means [selfUser] has access to [user]'s real email,
+        // while a null value doesn't necessarily mean it doesn't have access
+        // to the email, ....
+        return user.deliveryEmail;
+      } else if (store.emailAddressVisibility == EmailAddressVisibility.everyone) {
+        // ... we have to also check for [PerAccountStore.emailAddressVisibility].
+        // See:
+        //   * https://github.com/zulip/zulip-mobile/pull/5515#discussion_r997731727
+        //   * https://chat.zulip.org/#narrow/stream/378-api-design/topic/email.20address.20visibility/near/1296133
+        return user.email;
+      } else {
+        return null;
+      }
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     final zulipLocalizations = ZulipLocalizations.of(context);
@@ -42,6 +75,7 @@ class ProfilePage extends StatelessWidget {
       return const _ProfileErrorPage();
     }
 
+    final displayEmail = _getDisplayEmailFor(user, store: store);
     final items = [
       Center(
         child: Avatar(userId: userId, size: 200, borderRadius: 200 / 8)),
@@ -50,7 +84,10 @@ class ProfilePage extends StatelessWidget {
         textAlign: TextAlign.center,
         style: _TextStyles.primaryFieldText
           .merge(weightVariableTextStyle(context, wght: 700))),
-      // TODO(#291) render email field
+      if (displayEmail != null)
+        Text(displayEmail,
+          textAlign: TextAlign.center,
+          style: _TextStyles.primaryFieldText),
       Text(roleToLabel(user.role, zulipLocalizations),
         textAlign: TextAlign.center,
         style: _TextStyles.primaryFieldText),

test/widgets/profile_test.dart

@@ -71,12 +71,14 @@ void main() {
 
   group('ProfilePage', () {
     testWidgets('page builds; profile page renders', (WidgetTester tester) async {
-      final user = eg.user(userId: 1, fullName: 'test user');
+      final user = eg.user(userId: 1, fullName: 'test user',
+        deliveryEmail: 'testuser@example.com');
 
       await setupPage(tester, users: [user], pageUserId: user.userId);
 
       check(because: 'find user avatar', find.byType(Avatar).evaluate()).length.equals(1);
       check(because: 'find user name', find.text('test user').evaluate()).isNotEmpty();
+      check(because: 'find user delivery email', find.text('testuser@example.com').evaluate()).isNotEmpty();
     });
 
     testWidgets('page builds; profile page renders with profileData', (WidgetTester tester) async {