[pigeon] Adds SwiftFunction annotation

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 4.0.3
+
+* Adds `@SwiftFunction` annotation for specifying custom swift function signature.
+
 ## 4.0.2
 
 * Fixes lint warnings.

packages/pigeon/lib/ast.dart

@@ -32,6 +32,7 @@ class Method extends Node {
     this.isAsynchronous = false,
     this.offset,
     this.objcSelector = '',
+    this.swiftFunction = '',
     this.taskQueueType = TaskQueueType.serial,
   });
 
@@ -53,14 +54,19 @@ class Method extends Node {
   /// An override for the generated objc selector (ex. "divideNumber:by:").
   String objcSelector;
 
+  /// An override for the generated swift function signature (ex. "divideNumber(_:by:)").
+  String swiftFunction;
+
   /// Specifies how handlers are dispatched with respect to threading.
   TaskQueueType taskQueueType;
 
   @override
   String toString() {
     final String objcSelectorStr =
         objcSelector.isEmpty ? '' : ' objcSelector:$objcSelector';
-    return '(Method name:$name returnType:$returnType arguments:$arguments isAsynchronous:$isAsynchronous$objcSelectorStr)';
+    final String swiftFunctionStr =
+        swiftFunction.isEmpty ? '' : ' swiftFunction:$swiftFunction';
+    return '(Method name:$name returnType:$returnType arguments:$arguments isAsynchronous:$isAsynchronous$objcSelectorStr swiftFuncton:$swiftFunctionStr)';
   }
 }
 

packages/pigeon/lib/pigeon_lib.dart

@@ -98,6 +98,19 @@ class ObjCSelector {
   final String value;
 }
 
+/// Metadata to annotate methods to control the signature used for Swift output.
+/// The number of components in the provided signature must match the number of
+/// arguments in the annotated method.
+/// For example:
+///   @SwiftFunction('setValue(_:for:)') double divide(int value, String key);
+class SwiftFunction {
+  /// Constructor.
+  const SwiftFunction(this.value);
+
+  /// The string representation of the function signature.
+  final String value;
+}
+
 /// Type of TaskQueue which determines how handlers are dispatched for
 /// HostApi's.
 enum TaskQueueType {
@@ -659,6 +672,17 @@ List<Error> _validateAst(Root root, String source) {
           ));
         }
       }
+      if (method.swiftFunction.isNotEmpty) {
+        final RegExp signatureRegex =
+            RegExp('\\w+ *\\((\\w+:){${method.arguments.length}}\\)');
+        if (!signatureRegex.hasMatch(method.swiftFunction)) {
+          result.add(Error(
+            message:
+                'Invalid function signature, expected ${method.arguments.length} arguments.',
+            lineNumber: _calculateLineNumberNullable(source, method.offset),
+          ));
+        }
+      }
       if (method.taskQueueType != TaskQueueType.serial &&
           api.location != ApiLocation.host) {
         result.add(Error(
@@ -941,6 +965,13 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
             .asNullable<dart_ast.SimpleStringLiteral>()
             ?.value ??
         '';
+    final String swiftFunction = _findMetadata(node.metadata, 'SwiftFunction')
+            ?.arguments
+            ?.arguments
+            .first
+            .asNullable<dart_ast.SimpleStringLiteral>()
+            ?.value ??
+        '';
     final dart_ast.ArgumentList? taskQueueArguments =
         _findMetadata(node.metadata, 'TaskQueue')?.arguments;
     final String? taskQueueTypeName = taskQueueArguments == null
@@ -967,6 +998,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
           arguments: arguments,
           isAsynchronous: isAsynchronous,
           objcSelector: objcSelector,
+          swiftFunction: swiftFunction,
           offset: node.offset,
           taskQueueType: taskQueueType));
     } else if (_currentClass != null) {

packages/pigeon/lib/swift_generator.dart

@@ -43,6 +43,44 @@ class SwiftOptions {
 /// Calculates the name of the codec that will be generated for [api].
 String _getCodecName(Api api) => '${api.name}Codec';
 
+/// Returns a new [Method] using the swift function signature from [func],
+/// ie the name of function e the strings between the semicolons.
+/// Example:
+///   _swiftMethod('@SwiftFunction('add(_:with:)') void add(int x, int y)')
+///   will return 'void add(int _ x, int with y)'
+///   which represents 'func add(_ x: Int32, with y: Int32) -> Void' in Swift.
+Method _swiftMethod(Method func) {
+  if (func.swiftFunction.isEmpty) {
+    return func;
+  } else {
+    final String argsCapturator =
+        repeat(r'(\w+):', func.arguments.length).join();
+    final RegExp signatureRegex = RegExp(r'(\w+) *\(' + argsCapturator + r'\)');
+    final RegExpMatch match = signatureRegex.firstMatch(func.swiftFunction)!;
+
+    final Iterable<String> customComponents = match
+        .groups(
+            List<int>.generate(func.arguments.length, (int index) => index + 2))
+        .whereType();
+
+    return Method(
+      name: match.group(1)!,
+      returnType: func.returnType,
+      arguments:
+          map2(func.arguments, customComponents, (NamedType t, String u) {
+        if (u == t.name) {
+          return t;
+        }
+
+        return NamedType(name: '$u ${t.name}', type: t.type);
+      }).toList(),
+      isAsynchronous: func.isAsynchronous,
+      offset: func.offset,
+      taskQueueType: func.taskQueueType,
+    );
+  }
+}
+
 /// Writes the codec classwill be used for encoding messages for the [api].
 /// Example:
 /// private class FooHostApiCodecReader: FlutterStandardReader {...}
@@ -601,6 +639,9 @@ void generateSwift(SwiftOptions options, Root root, StringSink sink) {
   for (final Api api in root.apis) {
     _writeCodec(indent, api, root);
     indent.addln('');
+
+    api.methods = api.methods.map(_swiftMethod).toList();
+
     writeApi(api, root);
   }
 

packages/pigeon/test/pigeon_lib_test.dart

@@ -910,6 +910,52 @@ abstract class Api {
     expect(results.root.apis[0].methods[0].objcSelector, equals('foobar'));
   });
 
+  test('custom swift invalid function signature', () {
+    const String code = '''
+@HostApi()
+abstract class Api {
+  @SwiftFunction('subtractValue(_:by:)')
+  void subtract(int x, int y);
+}
+''';
+    final ParseResults results = _parseSource(code);
+    expect(results.errors.length, 0);
+    expect(results.root.apis.length, 1);
+    expect(results.root.apis[0].methods.length, equals(1));
+    expect(results.root.apis[0].methods[0].swiftFunction,
+        equals('subtractValue(_:by:)'));
+  });
+
+  test('custom swift invalid function signature', () {
+    const String code = '''
+@HostApi()
+abstract class Api {
+  @SwiftFunction('subtractValue(_:by:error:)')
+  void subtract(int x, int y);
+}
+''';
+    final ParseResults results = _parseSource(code);
+    expect(results.errors.length, 1);
+    expect(results.errors[0].lineNumber, 3);
+    expect(results.errors[0].message,
+        contains('Invalid function signature, expected 2 arguments'));
+  });
+
+  test('custom swift function signature no arguments', () {
+    const String code = '''
+@HostApi()
+abstract class Api {
+  @SwiftFunction('foobar()')
+  void initialize();
+}
+''';
+    final ParseResults results = _parseSource(code);
+    expect(results.errors.length, 0);
+    expect(results.root.apis.length, 1);
+    expect(results.root.apis[0].methods.length, equals(1));
+    expect(results.root.apis[0].methods[0].swiftFunction, equals('foobar()'));
+  });
+
   test('dart test has copyright', () {
     final Root root = Root(apis: <Api>[], classes: <Class>[], enums: <Enum>[]);
     const PigeonOptions options = PigeonOptions(

packages/pigeon/test/swift_generator_test.dart

@@ -947,4 +947,99 @@ void main() {
     final String code = sink.toString();
     expect(code, contains('var input: String\n'));
   });
+
+  test('swift function signature', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+            name: 'set',
+            arguments: <NamedType>[
+              NamedType(
+                type: const TypeDeclaration(
+                  baseName: 'int',
+                  isNullable: false,
+                ),
+                name: 'value',
+                offset: null,
+              ),
+              NamedType(
+                type: const TypeDeclaration(
+                  baseName: 'String',
+                  isNullable: false,
+                ),
+                name: 'key',
+                offset: null,
+              ),
+            ],
+            swiftFunction: 'setValue(_:for:)',
+            returnType: const TypeDeclaration.voidDeclaration(),
+            isAsynchronous: false,
+          )
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const SwiftOptions swiftOptions = SwiftOptions();
+    generateSwift(swiftOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('func setValue(_ value: Int32, for key: String)'));
+  });
+
+  test('swift function signature with same name argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+            name: 'set',
+            arguments: <NamedType>[
+              NamedType(
+                type: const TypeDeclaration(
+                  baseName: 'String',
+                  isNullable: false,
+                ),
+                name: 'key',
+                offset: null,
+              ),
+            ],
+            swiftFunction: 'removeValue(key:)',
+            returnType: const TypeDeclaration.voidDeclaration(),
+            isAsynchronous: false,
+          )
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const SwiftOptions swiftOptions = SwiftOptions();
+    generateSwift(swiftOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('func removeValue(key: String)'));
+  });
+
+  test('swift function signature with no arguments', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+            name: 'clear',
+            arguments: <NamedType>[],
+            swiftFunction: 'removeAll()',
+            returnType: const TypeDeclaration.voidDeclaration(),
+            isAsynchronous: false,
+          )
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const SwiftOptions swiftOptions = SwiftOptions();
+    generateSwift(swiftOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('func removeAll()'));
+  });
 }