content: Open links in-app on Android

`url_launcher` plugin now supports the desired behavior, which is using
Android Custom Tabs, so we don't need the workaround of opening the
links in external browser anymore, thus removed them.

Fixes: zulip#279

Author: rajveermalviya

lib/widgets/content.dart

@@ -680,15 +680,7 @@ void _launchUrl(BuildContext context, String urlString) async {
   bool launched = false;
   String? errorMessage;
   try {
-    launched = await ZulipBinding.instance.launchUrl(url,
-      mode: switch (Theme.of(context).platform) {
-        // TODO(#279): On Android we settle for LaunchMode.externalApplication
-        //   because url_launcher's in-app is a weirdly bare UX.
-        //   Switch once that's fixed upstream (by us or otherwise).
-        TargetPlatform.android => UrlLaunchMode.externalApplication,
-        _ => UrlLaunchMode.platformDefault,
-      },
-    );
+    launched = await ZulipBinding.instance.launchUrl(url);
   } on PlatformException catch (e) {
     errorMessage = e.message;
   }

test/widgets/content_test.dart

@@ -1,7 +1,6 @@
 import 'dart:io';
 
 import 'package:checks/checks.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -64,8 +63,6 @@ void main() {
   });
 
   group('LinkNode interactions', () {
-    const expectedModeAndroid = LaunchMode.externalApplication;
-
     // The Flutter test font uses square glyphs, so width equals height:
     //   https://github.com/flutter/flutter/wiki/Flutter-Test-Fonts
     const fontSize = 48.0;
@@ -89,10 +86,8 @@ void main() {
         '<p><a href="https://example/">hello</a></p>');
 
       await tester.tap(find.text('hello'));
-      final expectedMode = defaultTargetPlatform == TargetPlatform.android ?
-        LaunchMode.externalApplication : LaunchMode.platformDefault;
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://example/'), mode: expectedMode));
+        .single.equals((url: Uri.parse('https://example/'), mode: LaunchMode.platformDefault));
     }, variant: const TargetPlatformVariant({TargetPlatform.android, TargetPlatform.iOS}));
 
     testWidgets('multiple links in paragraph', (tester) async {
@@ -106,19 +101,19 @@ void main() {
 
       await tester.tapAt(base.translate(1*fontSize, 0)); // "fXo bar baz"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
 
       await tester.tapAt(base.translate(9*fontSize, 0)); // "foo bar bXz"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://b/'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('https://b/'), mode: LaunchMode.platformDefault));
     });
 
     testWidgets('link nested in other spans', (tester) async {
       await prepareContent(tester,
         '<p><strong><em><a href="https://a/">word</a></em></strong></p>');
       await tester.tap(find.text('word'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
     });
 
     testWidgets('link containing other spans', (tester) async {
@@ -129,27 +124,27 @@ void main() {
 
       await tester.tapAt(base.translate(1*fontSize, 0)); // "tXo words"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
 
       await tester.tapAt(base.translate(6*fontSize, 0)); // "two woXds"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
     });
 
     testWidgets('relative links are resolved', (tester) async {
       await prepareContent(tester,
         '<p><a href="/a/b?c#d">word</a></p>');
       await tester.tap(find.text('word'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('${eg.realmUrl}a/b?c#d'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('${eg.realmUrl}a/b?c#d'), mode: LaunchMode.platformDefault));
     });
 
     testWidgets('link inside HeadingNode', (tester) async {
       await prepareContent(tester,
         '<h6><a href="https://a/">word</a></h6>');
       await tester.tap(find.text('word'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
     });
 
     testWidgets('error dialog if invalid link', (tester) async {
@@ -159,7 +154,7 @@ void main() {
       await tester.tap(find.text('word'));
       await tester.pump();
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('file:///etc/bad'), mode: expectedModeAndroid));
+        .single.equals((url: Uri.parse('file:///etc/bad'), mode: LaunchMode.platformDefault));
       checkErrorDialog(tester, expectedTitle: 'Unable to open link');
     });
   });
@@ -206,7 +201,7 @@ void main() {
       await tester.tap(find.text('invalid'));
       final expectedUrl = eg.realmUrl.resolve('/#narrow/stream/1-check/topic');
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: expectedUrl, mode: LaunchMode.externalApplication));
+        .single.equals((url: expectedUrl, mode: LaunchMode.platformDefault));
       check(pushedRoutes).isEmpty();
     });
   });

test/widgets/profile_test.dart

@@ -1,5 +1,4 @@
 import 'package:checks/checks.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -167,10 +166,10 @@ void main() {
       );
 
       await tester.tap(find.text(testUrl));
-      final expectedMode = defaultTargetPlatform == TargetPlatform.android ?
-        LaunchMode.externalApplication : LaunchMode.platformDefault;
-      check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse(testUrl), mode: expectedMode));
+      check(testBinding.takeLaunchUrlCalls()).single.equals((
+        url: Uri.parse(testUrl),
+        mode: LaunchMode.platformDefault,
+      ));
     });
 
     testWidgets('page builds; external link type navigates away', (WidgetTester tester) async {
@@ -194,10 +193,10 @@ void main() {
       );
 
       await tester.tap(find.text('externalValue'));
-      final expectedMode = defaultTargetPlatform == TargetPlatform.android ?
-        LaunchMode.externalApplication : LaunchMode.platformDefault;
-      check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('http://example/externalValue'), mode: expectedMode));
+      check(testBinding.takeLaunchUrlCalls()).single.equals((
+        url: Uri.parse('http://example/externalValue'),
+        mode: LaunchMode.platformDefault,
+      ));
     });
 
     testWidgets('page builds; user links to profile', (WidgetTester tester) async {