[pigeon] adds generate option for example pigeons (flutter#4370)

Adds simple command for generating example files. Also adds arguments to choose what files to generate when running the generate function (test or example) runs both by default.

- [] I updated `CHANGELOG.md` to add a description of the change, [following repository CHANGELOG style].
- [] I added new tests to check the change I am making, or this PR is [test-exempt].

Author: tarrinneal

packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
 import android.util.Log;

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

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
 

packages/pigeon/example/app/ios/Runner/Messages.g.swift

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
 import Foundation

packages/pigeon/example/app/lib/src/messages.g.dart

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 // ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
 

packages/pigeon/example/app/macos/Runner/messages.g.h

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
 #import <Foundation/Foundation.h>

packages/pigeon/example/app/macos/Runner/messages.g.m

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
 #import "messages.g.h"

packages/pigeon/example/app/windows/runner/messages.g.cpp

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
 #undef _HAS_EXCEPTIONS

packages/pigeon/example/app/windows/runner/messages.g.h

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v10.1.2), do not edit directly.
+// Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
 #ifndef PIGEON_MESSAGES_G_H_

packages/pigeon/tool/generate.dart

@@ -19,12 +19,21 @@ import 'shared/generation.dart';
 
 const String _helpFlag = 'help';
 const String _formatFlag = 'format';
+const String _files = 'files';
+const String _test = 'test';
+const String _example = 'example';
+
+const List<String> _fileGroups = <String>[_test, _example];
 
 Future<void> main(List<String> args) async {
   final ArgParser parser = ArgParser()
     ..addFlag(_formatFlag, abbr: 'f', help: 'Autoformats after generation.')
     ..addFlag(_helpFlag,
-        negatable: false, abbr: 'h', help: 'Print this reference.');
+        negatable: false, abbr: 'h', help: 'Print this reference.')
+    ..addMultiOption(_files,
+        help:
+            'Select specific groups of files to generate; $_test or $_example. Defaults to both.',
+        allowed: _fileGroups);
 
   final ArgResults argResults = parser.parse(args);
   if (argResults.wasParsed(_helpFlag)) {
@@ -37,13 +46,29 @@ ${parser.usage}''');
 
   final String baseDir = p.dirname(p.dirname(Platform.script.toFilePath()));
 
-  print('Generating platform_test/ output...');
-  final int generateExitCode = await generateTestPigeons(baseDir: baseDir);
-  if (generateExitCode == 0) {
-    print('Generation complete!');
-  } else {
-    print('Generation failed; see above for errors.');
-    exit(generateExitCode);
+  final List<String>? toGenerate =
+      argResults.wasParsed(_files) ? argResults[_files] as List<String> : null;
+
+  if (toGenerate == null || toGenerate.contains(_test)) {
+    print('Generating platform_test/ output...');
+    final int generateExitCode = await generateTestPigeons(baseDir: baseDir);
+    if (generateExitCode == 0) {
+      print('Generation complete!');
+    } else {
+      print('Generation failed; see above for errors.');
+      exit(generateExitCode);
+    }
+  }
+
+  if (toGenerate == null || toGenerate.contains(_example)) {
+    print('Generating example/ output...');
+    final int generateExitCode = await generateExamplePigeons();
+    if (generateExitCode == 0) {
+      print('Generation complete!');
+    } else {
+      print('Generation failed; see above for errors.');
+      exit(generateExitCode);
+    }
   }
 
   if (argResults.wasParsed(_formatFlag)) {

packages/pigeon/tool/run_tests.dart

@@ -90,10 +90,7 @@ Future<void> _validateGeneratedExampleFiles() async {
   print('Validating generated files:');
   print('  Generating example output...');
 
-  final int generateExitCode = await runPigeon(
-    input: './example/app/pigeons/messages.dart',
-    basePath: './example/app',
-  );
+  final int generateExitCode = await generateExamplePigeons();
 
   if (generateExitCode != 0) {
     print('Generation failed; see above for errors.');