[pigeon] Fixes compilation error with unbounded type parameter for InstanceManager (#10483)

`IdentityWeakReference` requires a nonnull value so the input to type parameter to `getInstance` has to be nonnull. Its hard to write a meaningful test since this only causes a compilation error on older Kotlin versions, but I added a unit test to make sure `getInstance` specifies nonnull. 

This fixes flutter/flutter#178756 once plugins update generated code.

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Author: bparrishMines

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 26.1.2
+
+* [kotlin] Fixes compilation error with unbounded type parameter for InstanceManager.
+
 ## 26.1.1
 
 * Updates supported `analyzer` versions to 8.x or 9.x.

packages/pigeon/lib/src/generator_tools.dart

@@ -15,7 +15,7 @@ import 'generator.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '26.1.1';
+const String pigeonVersion = '26.1.2';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {

packages/pigeon/lib/src/kotlin/templates.dart

@@ -180,7 +180,7 @@ class ${kotlinInstanceManagerClassName(options)}(private val finalizationListene
   }
 
   /** Retrieves the instance associated with identifier, if present, otherwise `null`. */
-  fun <T> getInstance(identifier: Long): T? {
+  fun <T : Any> getInstance(identifier: Long): T? {
     logWarningIfFinalizationListenerHasStopped()
     val instance = weakInstances[identifier] as IdentityWeakReference<T>?
     return instance?.get()

packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/ProxyApiTests.gen.kt

@@ -214,7 +214,7 @@ class ProxyApiTestsPigeonInstanceManager(
   }
 
   /** Retrieves the instance associated with identifier, if present, otherwise `null`. */
-  fun <T> getInstance(identifier: Long): T? {
+  fun <T : Any> getInstance(identifier: Long): T? {
     logWarningIfFinalizationListenerHasStopped()
     val instance = weakInstances[identifier] as IdentityWeakReference<T>?
     return instance?.get()

packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/InstanceManagerTest.kt

@@ -145,7 +145,7 @@ class InstanceManagerTest {
     instanceManager.clearFinalizedWeakReferencesInterval = 1000
     instanceManager.stopFinalizationListener()
 
-    assertNull(instanceManager.getInstance<Any?>(0))
+    assertNull(instanceManager.getInstance(0))
     assertFalse(finalizerRan)
   }
 

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: 26.1.1 # This must match the version in lib/src/generator_tools.dart
+version: 26.1.2 # This must match the version in lib/src/generator_tools.dart
 
 environment:
   sdk: ^3.8.0

packages/pigeon/test/kotlin/proxy_api_test.dart

@@ -1070,6 +1070,36 @@ void main() {
           );
         },
       );
+
+      test('InstanceManager.getInstance specifies nonnull type', () {
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              constructors: <Constructor>[],
+              fields: <ApiField>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const KotlinGenerator generator = KotlinGenerator();
+        generator.generate(
+          const InternalKotlinOptions(kotlinOut: ''),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+
+        expect(
+          collapsedCode,
+          contains('fun <T : Any> getInstance(identifier: Long): T?'),
+        );
+      });
     });
   });
 }