Added experimental code generator tool for platform channels: Pigeon

packages/pigeon/.gitignore

@@ -0,0 +1,2 @@
+build/
+e2e_tests/test_objc/ios/Flutter/

packages/pigeon/CHANGELOG.md

@@ -0,0 +1,3 @@
+## 0.1.0-experimental.0
+
+* Initial release.

packages/pigeon/LICENSE

@@ -0,0 +1,27 @@
+Copyright 2019 The Chromium Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/pigeon/README.md

@@ -0,0 +1,126 @@
+# Pigeon
+
+<aside class="warning">
+Pigeon is experimental and unsupported.  It can be removed or changed at any time.
+</aside>
+
+Pigeon is a code generator tool to make communication between Flutter and the
+host platform type-safe and easier.
+
+## Supported Platforms
+
+Currently Pigeon only supports generating Objective-C code for usage on iOS and calling host functions from Flutter.
+
+## Runtime Requirements
+
+Pigeon generates all the code that is needed to communicate between Flutter and the host platform, there is no extra runtime requirement.  A plugin author doesn't need to worry about conflicting versions of Pigeon.
+
+## Usage
+
+### Steps
+
+1) Add Pigeon as a dev_dependency.
+1) Make a ".dart" file outside of your "lib" directory for defining the communication interface.
+1) Run pigeon on your ".dart" file to generate the required Dart and Objective-C code.
+1) Add the generated code to your `ios/Runner.xcworkspace` XCode project for compilation.
+1) Implement the generated iOS protocol for handling the calls on iOS, set it up
+   as the handler for the messages.
+1) Call the generated Dart methods.
+
+### Rules for defining your communication interface
+
+1) The file should contain no methods or function definitions.
+1) Datatypes are defined as classes with fields of the supported datatypes (see
+   the supported Datatypes section).
+1) Api's should be defined as an `abstract class` with either `HostApi()` or
+   `FlutterApi()` as metadata.  The former being for procedures that are defined
+   on the host platform and the latter for procedures that are defined in Dart.
+1) Method declarations on the Api classes should have one argument and a return
+   value whose types are defined in the file.
+
+### Example
+
+#### message.dart
+
+```dart
+import 'package:pigeon/pigeon_lib.dart';
+
+class SearchRequest {
+  String query;
+}
+
+class SearchReply {
+  String result;
+}
+
+@HostApi()
+abstract class Api {
+  SearchReply search(SearchRequest request);
+}
+```
+
+#### invocation
+
+```sh
+pub run pigeon \
+  --input pigeons/message.dart \
+  --dart_out lib/pigeon.dart \
+  --objc_header_out ios/Runner/pigeon.h \
+  --objc_source_out ios/Runner/pigeon.m
+```
+
+#### AppDelegate.m
+
+```objc
+#import "AppDelegate.h"
+#import <Flutter/Flutter.h>
+#import "pigeon.h"
+
+@interface MyApi : NSObject <Api>
+@end
+
+@implementation MyApi
+-(SearchReply*)search:(SearchRequest*)request {
+  SearchReply *reply = [[SearchReply alloc] init];
+  reply.result =
+      [NSString stringWithFormat:@"Hi %@!", request.query];
+  return reply;
+}
+@end
+
+- (BOOL)application:(UIApplication *)application 
+didFinishLaunchingWithOptions:(NSDictionary<UIApplicationLaunchOptionsKey, id> *)launchOptions {
+  MyApi *api = [[MyApi alloc] init];
+  ApiSetup(getFlutterEngine().binaryMessenger, api);
+  return YES;
+}
+```
+
+#### test.dart
+
+```dart
+import 'pigeon.dart';
+
+void main() {
+  testWidgets("test pigeon", (WidgetTester tester) async {
+    SearchRequest request = SearchRequest()..query = "Aaron";
+    Api api = Api();
+    SearchReply reply = await api.search(request);
+    expect(reply.result, equals("Hi Aaron!"));
+  });
+}
+
+```
+
+## Supported Datatypes
+
+Pigeon uses the `StandardMessageCodec` so it supports any data-type platform
+channels supports
+[[documentation](https://flutter.dev/docs/development/platform-integration/platform-channels#codec)].  Nested data-types are supported, too.
+
+Note: Generics for List and Map aren't supported yet.
+
+## Feedback
+
+File an issue in [flutter/flutter](https://github.com/flutter/flutter) with the
+word 'pigeon' clearly in the title and cc **@gaaclarke**.

packages/pigeon/bin/pigeon.dart

@@ -0,0 +1,32 @@
+// Copyright 2020 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.
+
+import 'dart:convert';
+import 'dart:io';
+import 'package:pigeon/pigeon_lib.dart';
+
+Future<void> main(List<String> args) async {
+  final PigeonOptions opts = Pigeon.parseArgs(args);
+  assert(opts.input != null);
+  final String importLine =
+      (opts.input != null) ? 'import \'${opts.input}\';\n' : '';
+  final String code = """$importLine
+import 'dart:io';
+import 'package:pigeon/pigeon_lib.dart';
+
+void main(List<String> args) async {
+  exit(await Pigeon.run(args));
+}
+""";
+  // TODO(aaclarke): Start using a system temp file.
+  const String tempFilename = '_pigeon_temp_.dart';
+  final File tempFile = await File(tempFilename).writeAsString(code);
+  final Process process =
+      await Process.start('dart', <String>[tempFilename] + args);
+  process.stdout.transform(utf8.decoder).listen((String data) => print(data));
+  process.stderr.transform(utf8.decoder).listen((String data) => print(data));
+  final int exitCode = await process.exitCode;
+  tempFile.deleteSync();
+  exit(exitCode);
+}

packages/pigeon/lib/ast.dart

@@ -0,0 +1,81 @@
+// Copyright 2020 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.
+
+/// Enum that represents where an [Api] is located, on the host or Flutter.
+enum ApiLocation {
+  /// The API is for calling functions defined on the host.
+  host,
+
+  /// The API is for calling functions defined in Flutter.
+  flutter,
+}
+
+/// Superclass for all AST nodes.
+class Node {}
+
+/// Represents a method on an [Api].
+class Method extends Node {
+  /// Parametric constructor for [Method].
+  Method({this.name, this.returnType, this.argType});
+
+  /// The name of the method.
+  String name;
+
+  /// The data-type of the return value.
+  String returnType;
+
+  /// The data-type of the argument.
+  String argType;
+}
+
+/// Represents a collection of [Method]s that are hosted ona given [location].
+class Api extends Node {
+  /// Parametric constructor for [Api].
+  Api({this.name, this.location, this.methods});
+
+  /// The name of the API.
+  String name;
+
+  /// Where the API's implementation is located, host or Flutter.
+  ApiLocation location;
+
+  /// List of methods inside the API.
+  List<Method> methods;
+}
+
+/// Represents a field on a [Class].
+class Field extends Node {
+  /// Parametric constructor for [Field].
+  Field({this.name, this.dataType});
+
+  /// The name of the field.
+  String name;
+
+  /// The data-type of the field (ex 'String' or 'int').
+  String dataType;
+}
+
+/// Represents a class with [Field]s.
+class Class extends Node {
+  /// Parametric constructor for [Class].
+  Class({this.name, this.fields});
+
+  /// The name of the class.
+  String name;
+
+  /// All the fields contained in the class.
+  List<Field> fields;
+}
+
+/// Top-level node for the AST.
+class Root extends Node {
+  /// Parametric constructor for [Root].
+  Root({this.classes, this.apis});
+
+  /// All the classes contained in the AST.
+  List<Class> classes;
+
+  /// All the API's contained in the AST.
+  List<Api> apis;
+}

packages/pigeon/lib/dart_generator.dart

@@ -0,0 +1,79 @@
+// Copyright 2020 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.
+
+import 'ast.dart';
+import 'generator_tools.dart';
+
+/// Generates Dart source code for the given AST represented by [root],
+/// outputting the code to [sink].
+void generateDart(Root root, StringSink sink) {
+  final List<String> customClassNames =
+      root.classes.map((Class x) => x.name).toList();
+  final Indent indent = Indent(sink);
+  indent.writeln('// Autogenerated from Dartle, do not edit directly.');
+  indent.writeln('import \'package:flutter/services.dart\';');
+  indent.writeln('');
+
+  for (Class klass in root.classes) {
+    sink.write('class ${klass.name} ');
+    indent.scoped('{', '}', () {
+      for (Field field in klass.fields) {
+        indent.writeln('${field.dataType} ${field.name};');
+      }
+      indent.write('Map _toMap() ');
+      indent.scoped('{', '}', () {
+        indent.writeln('Map dartleMap = Map();');
+        for (Field field in klass.fields) {
+          indent.write('dartleMap["${field.name}"] = ');
+          if (customClassNames.contains(field.dataType)) {
+            indent.addln('${field.name}._toMap();');
+          } else {
+            indent.addln('${field.name};');
+          }
+        }
+        indent.writeln('return dartleMap;');
+      });
+      indent.write('static ${klass.name} _fromMap(Map dartleMap) ');
+      indent.scoped('{', '}', () {
+        indent.writeln('var result = ${klass.name}();');
+        for (Field field in klass.fields) {
+          indent.write('result.${field.name} = ');
+          if (customClassNames.contains(field.dataType)) {
+            indent.addln(
+                '${field.dataType}._fromMap(dartleMap["${field.name}"]);');
+          } else {
+            indent.addln('dartleMap["${field.name}"];');
+          }
+        }
+        indent.writeln('return result;');
+      });
+    });
+    indent.writeln('');
+  }
+  for (Api api in root.apis) {
+    if (api.location == ApiLocation.host) {
+      indent.write('class ${api.name} ');
+      indent.scoped('{', '}', () {
+        for (Method func in api.methods) {
+          indent.write(
+              'Future<${func.returnType}> ${func.name}(${func.argType} arg) async ');
+          indent.scoped('{', '}', () {
+            indent.writeln('Map requestMap = arg._toMap();');
+            final String channelName = makeChannelName(api, func);
+            indent.writeln('BasicMessageChannel channel =');
+            indent.inc();
+            indent.inc();
+            indent.writeln(
+                'BasicMessageChannel(\'$channelName\', StandardMessageCodec());');
+            indent.dec();
+            indent.dec();
+            indent.writeln('Map replyMap = await channel.send(requestMap);');
+            indent.writeln('return ${func.returnType}._fromMap(replyMap);');
+          });
+        }
+      });
+      indent.writeln('');
+    }
+  }
+}