[pigeon] Allows swift generator to skip error class generation (#7849)

Since the Kotlin generator allows skipping error class generation, it makes sense for the Swift generator to have the same option.

Related to:
#6183 
flutter/flutter#142099

Author: wamynobe

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 22.6.0
+
+* [swift] Adds `includeErrorClass` to `SwiftOptions`.
+
 ## 22.5.0
 
 * [swift] Adds implementation for `@ProxyApi`.

packages/pigeon/lib/generator_tools.dart

@@ -14,7 +14,7 @@ import 'ast.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '22.5.0';
+const String pigeonVersion = '22.6.0';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {

packages/pigeon/lib/pigeon_lib.dart

@@ -745,6 +745,7 @@ class SwiftGeneratorAdapter implements GeneratorAdapter {
               path.posix.join(options.basePath ?? '', options.copyrightHeader))
           : null,
       errorClassName: swiftOptions.errorClassName,
+      includeErrorClass: swiftOptions.includeErrorClass,
     ));
     const SwiftGenerator generator = SwiftGenerator();
     generator.generate(

packages/pigeon/lib/swift_generator.dart

@@ -28,6 +28,7 @@ class SwiftOptions {
     this.copyrightHeader,
     this.fileSpecificClassNameComponent,
     this.errorClassName,
+    this.includeErrorClass = true,
   });
 
   /// A copyright header that will get prepended to generated code.
@@ -39,6 +40,12 @@ class SwiftOptions {
   /// The name of the error class used for passing custom error parameters.
   final String? errorClassName;
 
+  /// Whether to include the error class in generation.
+  ///
+  /// This should only ever be set to false if you have another generated
+  /// Swift file in the same directory.
+  final bool includeErrorClass;
+
   /// Creates a [SwiftOptions] from a Map representation where:
   /// `x = SwiftOptions.fromList(x.toMap())`.
   static SwiftOptions fromList(Map<String, Object> map) {
@@ -47,6 +54,7 @@ class SwiftOptions {
       fileSpecificClassNameComponent:
           map['fileSpecificClassNameComponent'] as String?,
       errorClassName: map['errorClassName'] as String?,
+      includeErrorClass: map['includeErrorClass'] as bool? ?? true,
     );
   }
 
@@ -58,6 +66,7 @@ class SwiftOptions {
       if (fileSpecificClassNameComponent != null)
         'fileSpecificClassNameComponent': fileSpecificClassNameComponent!,
       if (errorClassName != null) 'errorClassName': errorClassName!,
+      'includeErrorClass': includeErrorClass,
     };
     return result;
   }
@@ -1303,7 +1312,9 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
         .any((Api api) => api.methods.isNotEmpty);
     final bool hasProxyApi = root.apis.any((Api api) => api is AstProxyApi);
 
-    _writePigeonError(generatorOptions, indent);
+    if (generatorOptions.includeErrorClass) {
+      _writePigeonError(generatorOptions, indent);
+    }
 
     if (hasHostApi || hasProxyApi) {
       _writeWrapResult(indent);

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: 22.5.0 # This must match the version in lib/generator_tools.dart
+version: 22.6.0 # This must match the version in lib/generator_tools.dart
 
 environment:
   sdk: ^3.3.0

packages/pigeon/tool/shared/generation.dart

@@ -91,7 +91,8 @@ Future<int> generateTestPigeons(
         ? 'FlutterError'
         : '${pascalCaseName}Error';
 
-    final bool swiftErrorUseDefaultErrorName = input == 'core_tests';
+    final bool swiftErrorUseDefaultErrorName =
+        input == 'core_tests' || input == 'background_platform_channels';
 
     final String? swiftErrorClassName =
         swiftErrorUseDefaultErrorName ? null : '${pascalCaseName}Error';
@@ -117,6 +118,7 @@ Future<int> generateTestPigeons(
           ? null
           : '$outputBase/ios/Classes/$pascalCaseName.gen.swift',
       swiftErrorClassName: swiftErrorClassName,
+      swiftIncludeErrorClass: input != 'core_tests',
       // Linux
       gobjectHeaderOut: skipLanguages.contains(GeneratorLanguage.gobject)
           ? null
@@ -148,6 +150,7 @@ Future<int> generateTestPigeons(
           ? null
           : '$outputBase/macos/Classes/$pascalCaseName.gen.swift',
       swiftErrorClassName: swiftErrorClassName,
+      swiftIncludeErrorClass: input != 'core_tests',
       suppressVersion: true,
       dartPackageName: 'pigeon_integration_tests',
       injectOverflowTypes: includeOverflow && input == 'core_tests',
@@ -212,6 +215,7 @@ Future<int> runPigeon({
   String? kotlinPackage,
   String? kotlinErrorClassName,
   bool kotlinIncludeErrorClass = true,
+  bool swiftIncludeErrorClass = true,
   String? swiftOut,
   String? swiftErrorClassName,
   String? cppHeaderOut,
@@ -272,6 +276,7 @@ Future<int> runPigeon({
       swiftOut: swiftOut,
       swiftOptions: SwiftOptions(
         errorClassName: swiftErrorClassName,
+        includeErrorClass: swiftIncludeErrorClass,
       ),
       basePath: basePath,
       dartPackageName: dartPackageName,