[url_launcher] Alternative to isMock

packages/url_launcher/url_launcher_platform_interface/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.0.4
+
+* Use an assertion to ensure `isMock` is not used in release builds.
+* Prevent `noSuchMethod` from being used to bypass `isMock`.
+
 ## 1.0.3
 
 * Minor DartDoc changes and add a lint for missing DartDocs.

packages/url_launcher/url_launcher_platform_interface/lib/url_launcher_platform_interface.dart

@@ -21,6 +21,8 @@ abstract class UrlLauncherPlatform {
   /// Mockito mocks are implementing this class with `implements` which is forbidden for anything
   /// other than mocks (see class docs). This property provides a backdoor for mockito mocks to
   /// skip the verification that the class isn't implemented with `implements`.
+  ///
+  /// This flag has no effect in release builds.
   @visibleForTesting
   bool get isMock => false;
 
@@ -36,9 +38,17 @@ abstract class UrlLauncherPlatform {
   // TODO(amirh): Extract common platform interface logic.
   // https://github.com/flutter/flutter/issues/43368
   static set instance(UrlLauncherPlatform instance) {
-    if (!instance.isMock) {
+    bool assertionsEnabled = false;
+    assert(() {
+      assertionsEnabled = true;
+      return true;
+    }());
+    if (!assertionsEnabled || !instance.isMock) {
       try {
-        instance._verifyProvidesDefaultImplementations();
+        if (_verificationToken != instance._verifyProvidesDefaultImplementations()) {
+          throw AssertionError(
+              'Platform interfaces must not be implemented with `implements`');
+        }
       } on NoSuchMethodError catch (_) {
         throw AssertionError(
             'Platform interfaces must not be implemented with `implements`');
@@ -79,5 +89,9 @@ abstract class UrlLauncherPlatform {
   //
   // This private method is called by the instance setter, which fails if the class is
   // implemented with `implements`.
-  void _verifyProvidesDefaultImplementations() {}
+  Object _verifyProvidesDefaultImplementations() => _verificationToken;
+
+  // Private object used to determine if `_verifyProvidesDefaultImplementations`
+  // has been overridden with `noSuchMethod`.
+  static Object _verificationToken = Object();
 }

packages/url_launcher/url_launcher_platform_interface/pubspec.yaml

@@ -4,7 +4,7 @@ author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/url_launcher/url_launcher_platform_interface
 # NOTE: We strongly prefer non-breaking changes, even at the expense of a
 # less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
-version: 1.0.3
+version: 1.0.4
 
 dependencies:
   flutter: