Reland: Always use new plugin schema for plugin template (#49832)

Now that the new schema is supported on the stable channel, and the old
schema is considered legacy, the template should always create plugins
using the new schema.

dev/devicelab/bin/tasks/gradle_non_android_plugin_test.dart

@@ -50,15 +50,20 @@ Future<void> main() async {
       final String pubspecString = pubspecFile.readAsStringSync();
 
       final StringBuffer iosOnlyPubspec = StringBuffer();
+      bool inAndroidSection = false;
+      const String pluginPlatformIndentation = '      ';
       for (final String line in pubspecString.split('\n')) {
-        if (line.startsWith('    androidPackage:')) {
+        // Skip everything in the Android section of the plugin platforms list.
+        if (line.startsWith('${pluginPlatformIndentation}android:')) {
+          inAndroidSection = true;
           continue;
         }
-        if (line.startsWith('    pluginClass:')) {
-          iosOnlyPubspec.write('    platforms:\n');
-          iosOnlyPubspec.write('      ios:\n');
-          iosOnlyPubspec.write('        pluginClass: IosOnlyPlugin\n');
-          continue;
+        if (inAndroidSection) {
+          if (line.startsWith('$pluginPlatformIndentation  ')) {
+            continue;
+          } else {
+            inAndroidSection = false;
+          }
         }
         iosOnlyPubspec.write('$line\n');
       }

packages/flutter_tools/lib/src/commands/create.dart

@@ -642,10 +642,6 @@ To edit platform code in an IDE see https://flutter.dev/developing-packages/#edi
       'web': web,
       'macos': macos,
       'year': DateTime.now().year,
-      // For now, the new plugin schema is only used when a desktop plugin is
-      // enabled. Once the new schema is supported on stable, this should be
-      // removed, and the new schema should always be used.
-      'useNewPluginSchema': macos,
       // If a desktop platform is included, add a workaround for #31366.
       // When Linux and Windows are added, we will need this workaround again.
       'includeTargetPlatformWorkaround': false,

packages/flutter_tools/templates/plugin/pubspec.yaml.tmpl

@@ -6,6 +6,7 @@ homepage:
 
 environment:
   sdk: ">=2.1.0 <3.0.0"
+  flutter: ">=1.10.0"
 
 dependencies:
   flutter:
@@ -21,23 +22,9 @@ dev_dependencies:
 # The following section is specific to Flutter.
 flutter:
   # This section identifies this Flutter project as a plugin project.
-{{^useNewPluginSchema}}
-  # The androidPackage and pluginClass identifiers should not ordinarily
-  # be modified. They are used by the tooling to maintain consistency when
-  # adding or updating assets for this project.
-  plugin:
-    androidPackage: {{androidIdentifier}}
-    pluginClass: {{pluginClass}}
-{{/useNewPluginSchema}}
-{{#useNewPluginSchema}}
   # The 'pluginClass' and Android 'package' identifiers should not ordinarily
   # be modified. They are used by the tooling to maintain consistency when
   # adding or updating assets for this project.
-  #
-  # NOTE: This new plugin description format is not supported on Flutter's
-  # stable channel as of 1.9.1. A plugin published using this format will not
-  # work for most clients until the next major stable release.
-  # However, it is required in order to declare macOS support.
   plugin:
     platforms:
       android:
@@ -45,9 +32,10 @@ flutter:
         pluginClass: {{pluginClass}}
       ios:
         pluginClass: {{pluginClass}}
+{{#macos}}
       macos:
         pluginClass: {{pluginClass}}
-{{/useNewPluginSchema}}
+{{/macos}}
 
   # To add assets to your plugin package, add an assets section, like this:
   # assets:

packages/flutter_tools/test/commands.shard/permeable/create_test.dart

@@ -645,6 +645,21 @@ void main() {
     FeatureFlags: () => TestFeatureFlags(isMacOSEnabled: false),
   });
 
+  testUsingContext('plugin uses new platform schema', () async {
+    Cache.flutterRoot = '../..';
+    when(mockFlutterVersion.frameworkRevision).thenReturn(frameworkRevision);
+    when(mockFlutterVersion.channel).thenReturn(frameworkChannel);
+
+    final CreateCommand command = CreateCommand();
+    final CommandRunner<void> runner = createTestCommandRunner(command);
+
+    await runner.run(<String>['create', '--no-pub', '--template=plugin', projectDir.path]);
+
+    final String pubspecContents = await globals.fs.directory(projectDir.path).childFile('pubspec.yaml').readAsString();
+
+    expect(pubspecContents.contains('platforms:'), true);
+  });
+
   testUsingContext('has correct content and formatting with module template', () async {
     Cache.flutterRoot = '../..';
     when(mockFlutterVersion.frameworkRevision).thenReturn(frameworkRevision);