[webview_flutter] Migrate to nnbd (flutter#3327)

Author: mehmetf

packages/webview_flutter/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.0.0-nullsafety
+
+* Migration to null-safety.
+
 ## 1.0.8
 
 * Update Flutter SDK constraint.

packages/webview_flutter/lib/platform_interface.dart

@@ -21,7 +21,8 @@ abstract class WebViewPlatformCallbacksHandler {
   /// Invoked by [WebViewPlatformController] when a navigation request is pending.
   ///
   /// If true is returned the navigation is allowed, otherwise it is blocked.
-  FutureOr<bool> onNavigationRequest({String url, bool isForMainFrame});
+  FutureOr<bool> onNavigationRequest(
+      {required String url, required bool isForMainFrame});
 
   /// Invoked by [WebViewPlatformController] when a page has started loading.
   void onPageStarted(String url);
@@ -103,8 +104,8 @@ class WebResourceError {
   /// A user should not need to instantiate this class, but will receive one in
   /// [WebResourceErrorCallback].
   WebResourceError({
-    @required this.errorCode,
-    @required this.description,
+    required this.errorCode,
+    required this.description,
     this.domain,
     this.errorType,
     this.failingUrl,
@@ -131,21 +132,21 @@ class WebResourceError {
   /// in Objective-C. See
   /// https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ErrorHandlingCocoa/ErrorObjectsDomains/ErrorObjectsDomains.html
   /// for more information on error handling on iOS.
-  final String domain;
+  final String? domain;
 
   /// Description of the error that can be used to communicate the problem to the user.
   final String description;
 
   /// The type this error can be categorized as.
   ///
   /// This will never be `null` on Android, but can be `null` on iOS.
-  final WebResourceErrorType errorType;
+  final WebResourceErrorType? errorType;
 
   /// Gets the URL for which the resource request was made.
   ///
   /// This value is not provided on iOS. Alternatively, you can keep track of
   /// the last values provided to [WebViewPlatformController.loadUrl].
-  final String failingUrl;
+  final String? failingUrl;
 }
 
 /// Interface for talking to the webview's platform implementation.
@@ -176,7 +177,7 @@ abstract class WebViewPlatformController {
   /// Throws an ArgumentError if `url` is not a valid URL string.
   Future<void> loadUrl(
     String url,
-    Map<String, String> headers,
+    Map<String, String>? headers,
   ) {
     throw UnimplementedError(
         "WebView loadUrl is not implemented on the current platform");
@@ -194,7 +195,7 @@ abstract class WebViewPlatformController {
   /// Accessor to the current URL that the WebView is displaying.
   ///
   /// If no URL was ever loaded, returns `null`.
-  Future<String> currentUrl() {
+  Future<String?> currentUrl() {
     throw UnimplementedError(
         "WebView currentUrl is not implemented on the current platform");
   }
@@ -281,7 +282,7 @@ abstract class WebViewPlatformController {
   }
 
   /// Returns the title of the currently loaded page.
-  Future<String> getTitle() {
+  Future<String?> getTitle() {
     throw UnimplementedError(
         "WebView getTitle is not implemented on the current platform");
   }
@@ -337,7 +338,7 @@ class WebSetting<T> {
       : _value = value,
         isPresent = true;
 
-  final T _value;
+  final T? _value;
 
   /// The setting's value.
   ///
@@ -347,7 +348,14 @@ class WebSetting<T> {
       throw StateError('Cannot access a value of an absent WebSetting');
     }
     assert(isPresent);
-    return _value;
+    // The intention of this getter is to return T whether it is nullable or
+    // not whereas _value is of type T? since _value can be null even when
+    // T is not nullable (when isPresent == false).
+    //
+    // We promote _value to T using `as T` instead of `!` operator to handle
+    // the case when _value is legitimately null (and T is a nullable type).
+    // `!` operator would always throw if _value is null.
+    return _value as T;
   }
 
   /// True when this web setting instance contains a value.
@@ -358,7 +366,7 @@ class WebSetting<T> {
   @override
   bool operator ==(Object other) {
     if (other.runtimeType != runtimeType) return false;
-    final WebSetting<T> typedOther = other;
+    final WebSetting<T> typedOther = other as WebSetting<T>;
     return typedOther.isPresent == isPresent && typedOther._value == _value;
   }
 
@@ -382,19 +390,19 @@ class WebSettings {
     this.hasNavigationDelegate,
     this.debuggingEnabled,
     this.gestureNavigationEnabled,
-    @required this.userAgent,
+    required this.userAgent,
   }) : assert(userAgent != null);
 
   /// The JavaScript execution mode to be used by the webview.
-  final JavascriptMode javascriptMode;
+  final JavascriptMode? javascriptMode;
 
   /// Whether the [WebView] has a [NavigationDelegate] set.
-  final bool hasNavigationDelegate;
+  final bool? hasNavigationDelegate;
 
   /// Whether to enable the platform's webview content debugging tools.
   ///
   /// See also: [WebView.debuggingEnabled].
-  final bool debuggingEnabled;
+  final bool? debuggingEnabled;
 
   /// The value used for the HTTP `User-Agent:` request header.
   ///
@@ -404,12 +412,12 @@ class WebSettings {
   /// last time it was set.
   ///
   /// See also [WebView.userAgent].
-  final WebSetting<String> userAgent;
+  final WebSetting<String?> userAgent;
 
   /// Whether to allow swipe based navigation in iOS.
   ///
   /// See also: [WebView.gestureNavigationEnabled]
-  final bool gestureNavigationEnabled;
+  final bool? gestureNavigationEnabled;
 
   @override
   String toString() {
@@ -428,7 +436,7 @@ class CreationParams {
   CreationParams({
     this.initialUrl,
     this.webSettings,
-    this.javascriptChannelNames,
+    this.javascriptChannelNames = const <String>{},
     this.userAgent,
     this.autoMediaPlaybackPolicy =
         AutoMediaPlaybackPolicy.require_user_action_for_all_media_types,
@@ -437,12 +445,12 @@ class CreationParams {
   /// The initialUrl to load in the webview.
   ///
   /// When null the webview will be created without loading any page.
-  final String initialUrl;
+  final String? initialUrl;
 
   /// The initial [WebSettings] for the new webview.
   ///
   /// This can later be updated with [WebViewPlatformController.updateSettings].
-  final WebSettings webSettings;
+  final WebSettings? webSettings;
 
   /// The initial set of JavaScript channels that are configured for this webview.
   ///
@@ -460,7 +468,7 @@ class CreationParams {
   /// The value used for the HTTP User-Agent: request header.
   ///
   /// When null the platform's webview default is used for the User-Agent header.
-  final String userAgent;
+  final String? userAgent;
 
   /// Which restrictions apply on automatic media playback.
   final AutoMediaPlaybackPolicy autoMediaPlaybackPolicy;
@@ -475,7 +483,7 @@ class CreationParams {
 ///
 /// See also the `onWebViewPlatformCreated` argument for [WebViewPlatform.build].
 typedef WebViewPlatformCreatedCallback = void Function(
-    WebViewPlatformController webViewPlatformController);
+    WebViewPlatformController? webViewPlatformController);
 
 /// Interface for a platform implementation of a WebView.
 ///
@@ -505,14 +513,14 @@ abstract class WebViewPlatform {
   ///
   /// `webViewPlatformHandler` must not be null.
   Widget build({
-    BuildContext context,
+    required BuildContext context,
     // TODO(amirh): convert this to be the actual parameters.
     // I'm starting without it as the PR is starting to become pretty big.
     // I'll followup with the conversion PR.
-    CreationParams creationParams,
-    @required WebViewPlatformCallbacksHandler webViewPlatformCallbacksHandler,
-    WebViewPlatformCreatedCallback onWebViewPlatformCreated,
-    Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers,
+    required CreationParams creationParams,
+    required WebViewPlatformCallbacksHandler webViewPlatformCallbacksHandler,
+    WebViewPlatformCreatedCallback? onWebViewPlatformCreated,
+    Set<Factory<OneSequenceGestureRecognizer>>? gestureRecognizers,
   });
 
   /// Clears all cookies for all [WebView] instances.

packages/webview_flutter/lib/src/webview_android.dart

@@ -20,11 +20,11 @@ import 'webview_method_channel.dart';
 class AndroidWebView implements WebViewPlatform {
   @override
   Widget build({
-    BuildContext context,
-    CreationParams creationParams,
-    @required WebViewPlatformCallbacksHandler webViewPlatformCallbacksHandler,
-    WebViewPlatformCreatedCallback onWebViewPlatformCreated,
-    Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers,
+    required BuildContext context,
+    required CreationParams creationParams,
+    required WebViewPlatformCallbacksHandler webViewPlatformCallbacksHandler,
+    WebViewPlatformCreatedCallback? onWebViewPlatformCreated,
+    Set<Factory<OneSequenceGestureRecognizer>>? gestureRecognizers,
   }) {
     assert(webViewPlatformCallbacksHandler != null);
     return GestureDetector(

packages/webview_flutter/lib/src/webview_cupertino.dart

@@ -20,11 +20,11 @@ import 'webview_method_channel.dart';
 class CupertinoWebView implements WebViewPlatform {
   @override
   Widget build({
-    BuildContext context,
-    CreationParams creationParams,
-    @required WebViewPlatformCallbacksHandler webViewPlatformCallbacksHandler,
-    WebViewPlatformCreatedCallback onWebViewPlatformCreated,
-    Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers,
+    required BuildContext context,
+    required CreationParams creationParams,
+    required WebViewPlatformCallbacksHandler webViewPlatformCallbacksHandler,
+    WebViewPlatformCreatedCallback? onWebViewPlatformCreated,
+    Set<Factory<OneSequenceGestureRecognizer>>? gestureRecognizers,
   }) {
     return UiKitView(
       viewType: 'plugins.flutter.io/webview',

packages/webview_flutter/lib/src/webview_method_channel.dart

@@ -25,31 +25,31 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
   static const MethodChannel _cookieManagerChannel =
       MethodChannel('plugins.flutter.io/cookie_manager');
 
-  Future<bool> _onMethodCall(MethodCall call) async {
+  Future<bool?> _onMethodCall(MethodCall call) async {
     switch (call.method) {
       case 'javascriptChannelMessage':
-        final String channel = call.arguments['channel'];
-        final String message = call.arguments['message'];
+        final String channel = call.arguments['channel']!;
+        final String message = call.arguments['message']!;
         _platformCallbacksHandler.onJavaScriptChannelMessage(channel, message);
         return true;
       case 'navigationRequest':
         return await _platformCallbacksHandler.onNavigationRequest(
-          url: call.arguments['url'],
-          isForMainFrame: call.arguments['isForMainFrame'],
+          url: call.arguments['url']!,
+          isForMainFrame: call.arguments['isForMainFrame']!,
         );
       case 'onPageFinished':
-        _platformCallbacksHandler.onPageFinished(call.arguments['url']);
+        _platformCallbacksHandler.onPageFinished(call.arguments['url']!);
         return null;
       case 'onPageStarted':
-        _platformCallbacksHandler.onPageStarted(call.arguments['url']);
+        _platformCallbacksHandler.onPageStarted(call.arguments['url']!);
         return null;
       case 'onWebResourceError':
         _platformCallbacksHandler.onWebResourceError(
           WebResourceError(
-            errorCode: call.arguments['errorCode'],
-            description: call.arguments['description'],
+            errorCode: call.arguments['errorCode']!,
+            description: call.arguments['description']!,
+            failingUrl: call.arguments['failingUrl']!,
             domain: call.arguments['domain'],
-            failingUrl: call.arguments['failingUrl'],
             errorType: call.arguments['errorType'] == null
                 ? null
                 : WebResourceErrorType.values.firstWhere(
@@ -71,7 +71,7 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
   @override
   Future<void> loadUrl(
     String url,
-    Map<String, String> headers,
+    Map<String, String>? headers,
   ) async {
     assert(url != null);
     return _channel.invokeMethod<void>('loadUrl', <String, dynamic>{
@@ -81,13 +81,15 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
   }
 
   @override
-  Future<String> currentUrl() => _channel.invokeMethod<String>('currentUrl');
+  Future<String?> currentUrl() => _channel.invokeMethod<String>('currentUrl');
 
   @override
-  Future<bool> canGoBack() => _channel.invokeMethod<bool>("canGoBack");
+  Future<bool> canGoBack() =>
+      _channel.invokeMethod<bool>("canGoBack").then((result) => result!);
 
   @override
-  Future<bool> canGoForward() => _channel.invokeMethod<bool>("canGoForward");
+  Future<bool> canGoForward() =>
+      _channel.invokeMethod<bool>("canGoForward").then((result) => result!);
 
   @override
   Future<void> goBack() => _channel.invokeMethod<void>("goBack");
@@ -102,18 +104,18 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
   Future<void> clearCache() => _channel.invokeMethod<void>("clearCache");
 
   @override
-  Future<void> updateSettings(WebSettings settings) {
+  Future<void> updateSettings(WebSettings settings) async {
     final Map<String, dynamic> updatesMap = _webSettingsToMap(settings);
-    if (updatesMap.isEmpty) {
-      return null;
+    if (updatesMap.isNotEmpty) {
+      await _channel.invokeMethod<void>('updateSettings', updatesMap);
     }
-    return _channel.invokeMethod<void>('updateSettings', updatesMap);
   }
 
   @override
   Future<String> evaluateJavascript(String javascriptString) {
-    return _channel.invokeMethod<String>(
-        'evaluateJavascript', javascriptString);
+    return _channel
+        .invokeMethod<String>('evaluateJavascript', javascriptString)
+        .then((result) => result!);
   }
 
   @override
@@ -129,7 +131,7 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
   }
 
   @override
-  Future<String> getTitle() => _channel.invokeMethod<String>("getTitle");
+  Future<String?> getTitle() => _channel.invokeMethod<String>("getTitle");
 
   @override
   Future<void> scrollTo(int x, int y) {
@@ -148,19 +150,21 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
   }
 
   @override
-  Future<int> getScrollX() => _channel.invokeMethod<int>("getScrollX");
+  Future<int> getScrollX() =>
+      _channel.invokeMethod<int>("getScrollX").then((result) => result!);
 
   @override
-  Future<int> getScrollY() => _channel.invokeMethod<int>("getScrollY");
+  Future<int> getScrollY() =>
+      _channel.invokeMethod<int>("getScrollY").then((result) => result!);
 
   /// Method channel implementation for [WebViewPlatform.clearCookies].
   static Future<bool> clearCookies() {
     return _cookieManagerChannel
         .invokeMethod<bool>('clearCookies')
-        .then<bool>((dynamic result) => result);
+        .then<bool>((dynamic result) => result!);
   }
 
-  static Map<String, dynamic> _webSettingsToMap(WebSettings settings) {
+  static Map<String, dynamic> _webSettingsToMap(WebSettings? settings) {
     final Map<String, dynamic> map = <String, dynamic>{};
     void _addIfNonNull(String key, dynamic value) {
       if (value == null) {
@@ -176,7 +180,7 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
       map[key] = setting.value;
     }
 
-    _addIfNonNull('jsMode', settings.javascriptMode?.index);
+    _addIfNonNull('jsMode', settings!.javascriptMode?.index);
     _addIfNonNull('hasNavigationDelegate', settings.hasNavigationDelegate);
     _addIfNonNull('debuggingEnabled', settings.debuggingEnabled);
     _addIfNonNull(