[pigeon] Improve style of generated Swift code

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 16.0.4
+
+* [swift] Improve style of Swift output.
+
 ## 16.0.3
 
 * [kotlin] Separates message call code generation into separate methods.

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

@@ -5,12 +5,13 @@
 // See also: https://pub.dev/packages/pigeon
 
 import Foundation
+
 #if os(iOS)
-import Flutter
+  import Flutter
 #elseif os(macOS)
-import FlutterMacOS
+  import FlutterMacOS
 #else
-#error("Unsupported platform.")
+  #error("Unsupported platform.")
 #endif
 
 private func wrapResult(_ result: Any?) -> [Any?] {
@@ -22,13 +23,13 @@ private func wrapError(_ error: Any) -> [Any?] {
     return [
       flutterError.code,
       flutterError.message,
-      flutterError.details
+      flutterError.details,
     ]
   }
   return [
     "\(error)",
     "\(type(of: error))",
-    "Stacktrace: \(Thread.callStackSymbols)"
+    "Stacktrace: \(Thread.callStackSymbols)",
   ]
 }
 
@@ -83,10 +84,10 @@ struct MessageData {
 private class ExampleHostApiCodecReader: FlutterStandardReader {
   override func readValue(ofType type: UInt8) -> Any? {
     switch type {
-      case 128:
-        return MessageData.fromList(self.readValue() as! [Any?])
-      default:
-        return super.readValue(ofType: type)
+    case 128:
+      return MessageData.fromList(self.readValue() as! [Any?])
+    default:
+      return super.readValue(ofType: type)
     }
   }
 }
@@ -165,10 +166,10 @@ class ExampleHostApiSetup {
         let messageArg = args[0] as! MessageData
         api.sendMessage(message: messageArg) { result in
           switch result {
-            case .success(let res):
-              reply(wrapResult(res))
-            case .failure(let error):
-              reply(wrapError(error))
+          case .success(let res):
+            reply(wrapResult(res))
+          case .failure(let error):
+            reply(wrapError(error))
           }
         }
       }
@@ -183,23 +184,23 @@ protocol MessageFlutterApiProtocol {
 }
 class MessageFlutterApi: MessageFlutterApiProtocol {
   private let binaryMessenger: FlutterBinaryMessenger
-  init(binaryMessenger: FlutterBinaryMessenger){
+  init(binaryMessenger: FlutterBinaryMessenger) {
     self.binaryMessenger = binaryMessenger
   }
   func flutterMethod(aString aStringArg: String?, completion: @escaping (Result<String, FlutterError>) -> Void) {
     let channelName: String = "dev.flutter.pigeon.pigeon_example_package.MessageFlutterApi.flutterMethod"
     let channel = FlutterBasicMessageChannel(name: channelName, binaryMessenger: binaryMessenger)
     channel.sendMessage([aStringArg] as [Any?]) { response in
       guard let listResponse = response as? [Any?] else {
-        completion(.failure(createConnectionError(withChannelName:channelName)))
+        completion(.failure(createConnectionError(withChannelName: channelName)))
         return
       }
-      if (listResponse.count > 1) {
+      if listResponse.count > 1 {
         let code: String = listResponse[0] as! String
         let message: String? = nilOrValue(listResponse[1])
         let details: String? = nilOrValue(listResponse[2])
-        completion(.failure(FlutterError(code: code, message: message, details: details)));
-      } else if (listResponse[0] == nil) {
+        completion(.failure(FlutterError(code: code, message: message, details: details)))
+      } else if listResponse[0] == nil {
         completion(.failure(FlutterError(code: "null-error", message: "Flutter api returned null value for non-null return value.", details: "")))
       } else {
         let result = listResponse[0] as! String

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 = '16.0.3';
+const String pigeonVersion = '16.0.4';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {
@@ -309,7 +309,7 @@ bool isVoid(TypeMirror type) {
 void addLines(Indent indent, Iterable<String> lines, {String? linePrefix}) {
   final String prefix = linePrefix ?? '';
   for (final String line in lines) {
-    indent.writeln('$prefix$line');
+    indent.writeln(line.isNotEmpty ? '$prefix$line' : prefix.trimRight());
   }
 }
 

packages/pigeon/lib/swift_generator.dart

@@ -76,13 +76,14 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
     required String dartPackageName,
   }) {
     indent.writeln('import Foundation');
+    indent.newln();
     indent.format('''
 #if os(iOS)
-import Flutter
+  import Flutter
 #elseif os(macOS)
-import FlutterMacOS
+  import FlutterMacOS
 #else
-#error("Unsupported platform.")
+  #error("Unsupported platform.")
 #endif''');
   }
 
@@ -160,6 +161,9 @@ import FlutterMacOS
     indent.addScoped('{', '}', () {
       indent.write('return ');
       indent.addScoped('[', ']', () {
+        // Follow swift-format style, which is to use a trailing comma unless
+        // there is only one element.
+        final String separator = classDefinition.fields.length > 1 ? ',' : '';
         for (final NamedType field
             in getFieldsInSerializationOrder(classDefinition)) {
           String toWriteValue = '';
@@ -173,7 +177,7 @@ import FlutterMacOS
             toWriteValue = field.name;
           }
 
-          indent.writeln('$toWriteValue,');
+          indent.writeln('$toWriteValue$separator');
         }
       });
     });
@@ -294,7 +298,7 @@ import FlutterMacOS
     indent.write('class ${api.name}: ${api.name}Protocol ');
     indent.addScoped('{', '}', () {
       indent.writeln('private let binaryMessenger: FlutterBinaryMessenger');
-      indent.write('init(binaryMessenger: FlutterBinaryMessenger)');
+      indent.write('init(binaryMessenger: FlutterBinaryMessenger) ');
       indent.addScoped('{', '}', () {
         indent.writeln('self.binaryMessenger = binaryMessenger');
       });
@@ -330,20 +334,20 @@ import FlutterMacOS
             indent.writeScoped(
                 'guard let listResponse = response as? [Any?] else {', '}', () {
               indent.writeln(
-                  'completion(.failure(createConnectionError(withChannelName:channelName)))');
+                  'completion(.failure(createConnectionError(withChannelName: channelName)))');
               indent.writeln('return');
             });
-            indent.writeScoped('if (listResponse.count > 1) {', '} ', () {
+            indent.writeScoped('if listResponse.count > 1 {', '} ', () {
               indent.writeln('let code: String = listResponse[0] as! String');
               indent.writeln(
                   'let message: String? = nilOrValue(listResponse[1])');
               indent.writeln(
                   'let details: String? = nilOrValue(listResponse[2])');
               indent.writeln(
-                  'completion(.failure(FlutterError(code: code, message: message, details: details)));');
+                  'completion(.failure(FlutterError(code: code, message: message, details: details)))');
             }, addTrailingNewline: false);
             if (!func.returnType.isNullable && !func.returnType.isVoid) {
-              indent.addScoped('else if (listResponse[0] == nil) {', '} ', () {
+              indent.addScoped('else if listResponse[0] == nil {', '} ', () {
                 indent.writeln(
                     'completion(.failure(FlutterError(code: "null-error", message: "Flutter api returned null value for non-null return value.", details: "")))');
               }, addTrailingNewline: false);
@@ -495,8 +499,14 @@ import FlutterMacOS
                 });
               }
               final String tryStatement = method.isAsynchronous ? '' : 'try ';
+              // Empty parens are not required when calling a method whose only
+              // argument is a trailing closure.
+              final String argumentString =
+                  methodArgument.isEmpty && method.isAsynchronous
+                      ? ''
+                      : '(${methodArgument.join(', ')})';
               final String call =
-                  '${tryStatement}api.${components.name}(${methodArgument.join(', ')})';
+                  '${tryStatement}api.${components.name}$argumentString';
               if (method.isAsynchronous) {
                 final String resultName =
                     method.returnType.isVoid ? 'nil' : 'res';
@@ -506,7 +516,7 @@ import FlutterMacOS
 
                 indent.addScoped('{ result in', '}', () {
                   indent.write('switch result ');
-                  indent.addScoped('{', '}', () {
+                  indent.addScoped('{', '}', nestCount: 0, () {
                     final String nullsafe =
                         method.returnType.isNullable ? '?' : '';
                     final String enumTag =
@@ -573,7 +583,7 @@ import FlutterMacOS
         indent.write('override func readValue(ofType type: UInt8) -> Any? ');
         indent.addScoped('{', '}', () {
           indent.write('switch type ');
-          indent.addScoped('{', '}', () {
+          indent.addScoped('{', '}', nestCount: 0, () {
             for (final EnumeratedClass customClass
                 in getCodecClasses(api, root)) {
               indent.writeln('case ${customClass.enumeration}:');
@@ -764,14 +774,14 @@ import FlutterMacOS
         indent.addScoped('[', ']', () {
           indent.writeln('flutterError.code,');
           indent.writeln('flutterError.message,');
-          indent.writeln('flutterError.details');
+          indent.writeln('flutterError.details,');
         });
       });
       indent.write('return ');
       indent.addScoped('[', ']', () {
         indent.writeln(r'"\(error)",');
         indent.writeln(r'"\(type(of: error))",');
-        indent.writeln(r'"Stacktrace: \(Thread.callStackSymbols)"');
+        indent.writeln(r'"Stacktrace: \(Thread.callStackSymbols)",');
       });
     });
   }