[pigeon] Kotlin/Java method overloading for the setUp method (#6843)

This PR allows Java code to call the Kotlin `setUp` method without the optional `messageChannelSuffix` parameter.

I am not 100% sure how the tests should be adjusted to accurately test the Java/Kotlin interop - any advice there would be welcome?

### Affected issues:
flutter/flutter#149027

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 19.0.2
+
+* [kotlin] Adds the `@JvmOverloads` to the `HostApi` setUp method. This prevents the calling Java code from having to provide an empty `String` as Kotlin provides it by default  
+
 ## 19.0.1
 
 * [dart] Updates `PigeonInstanceMangerApi` to use the shared api channel code.

packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt

@@ -118,6 +118,7 @@ interface ExampleHostApi {
     /** The codec used by ExampleHostApi. */
     val codec: MessageCodec<Any?> by lazy { ExampleHostApiCodec }
     /** Sets up an instance of `ExampleHostApi` to handle messages through the `binaryMessenger`. */
+    @JvmOverloads
     fun setUp(
         binaryMessenger: BinaryMessenger,
         api: ExampleHostApi?,

packages/pigeon/lib/generator_tools.dart

@@ -13,7 +13,7 @@ import 'ast.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '19.0.1';
+const String pigeonVersion = '19.0.2';
 
 /// Prefix for all local variables in methods.
 ///

packages/pigeon/lib/kotlin_generator.dart

@@ -430,6 +430,7 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         });
         indent.writeln(
             '/** Sets up an instance of `$apiName` to handle messages through the `binaryMessenger`. */');
+        indent.writeln('@JvmOverloads');
         indent.write(
             'fun setUp(binaryMessenger: BinaryMessenger, api: $apiName?, messageChannelSuffix: String = "") ');
         indent.addScoped('{', '}', () {

packages/pigeon/pubspec.yaml

@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+pigeon%22
-version: 19.0.1 # This must match the version in lib/generator_tools.dart
+version: 19.0.2 # This must match the version in lib/generator_tools.dart
 
 environment:
   sdk: ^3.2.0

packages/pigeon/test/kotlin_generator_test.dart

@@ -231,6 +231,10 @@ void main() {
     final String code = sink.toString();
     expect(code, contains('interface Api'));
     expect(code, contains('fun doSomething(input: Input): Output'));
+    expect(code, contains('''
+    @JvmOverloads
+    fun setUp(binaryMessenger: BinaryMessenger, api: Api?, messageChannelSuffix: String = "") {
+    '''));
     expect(code, contains('channel.setMessageHandler'));
     expect(code, contains('''
         if (api != null) {