packages/pigeon/lib/dart_generator.dart - mirrors/packages - Git at Google

 // 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.

 import 'ast.dart';
 import 'functional.dart';
 import 'generator_tools.dart';

 /// Options that control how Dart code will be generated.
 class DartOptions {
   /// Constructor for DartOptions.
   const DartOptions({this.isNullSafe = true, this.copyrightHeader});

   /// Determines if the generated code has null safety annotations (Dart >=2.12 required).
   final bool isNullSafe;

   /// A copyright header that will get prepended to generated code.
   final Iterable<String>? copyrightHeader;

   /// Creates a [DartOptions] from a Map representation where:
   /// `x = DartOptions.fromMap(x.toMap())`.
   static DartOptions fromMap(Map<String, Object> map) {
     return DartOptions(
       isNullSafe: map['isNullSafe'] as bool? ?? true,
       copyrightHeader: map['copyrightHeader'] as Iterable<String>?,
     );
   }

   /// Converts a [DartOptions] to a Map representation where:
   /// `x = DartOptions.fromMap(x.toMap())`.
   Map<String, Object> toMap() {
     final Map<String, Object> result = <String, Object>{
       if (isNullSafe != null) 'isNullSafe': isNullSafe,
       if (copyrightHeader != null) 'copyrightHeader': copyrightHeader!,
     };
     return result;
   }

   /// Overrides any non-null parameters from [options] into this to make a new
   /// [DartOptions].
   DartOptions merge(DartOptions options) {
     return DartOptions.fromMap(mergeMaps(toMap(), options.toMap()));
   }
 }

 String _escapeForDartSingleQuotedString(String raw) {
   return raw
       .replaceAll(r'\', r'\\')
       .replaceAll(r'$', r'\$')
       .replaceAll(r"'", r"\'");
 }

 String _getCodecName(Api api) => '_${api.name}Codec';

 void _writeCodec(Indent indent, String codecName, Api api, Root root) {
   indent.write('class $codecName extends StandardMessageCodec ');
   indent.scoped('{', '}', () {
     indent.writeln('const $codecName();');
     if (getCodecClasses(api, root).isNotEmpty) {
       indent.writeln('@override');
       indent.write('void writeValue(WriteBuffer buffer, Object? value) ');
       indent.scoped('{', '}', () {
         for (final EnumeratedClass customClass in getCodecClasses(api, root)) {
           indent.write('if (value is ${customClass.name}) ');
           indent.scoped('{', '} else ', () {
             indent.writeln('buffer.putUint8(${customClass.enumeration});');
             indent.writeln('writeValue(buffer, value.encode());');
           });
         }
         indent.scoped('{', '}', () {
           indent.writeln('super.writeValue(buffer, value);');
         });
       });
       indent.writeln('@override');
       indent.write('Object? readValueOfType(int type, ReadBuffer buffer) ');
       indent.scoped('{', '}', () {
         indent.write('switch (type) ');
         indent.scoped('{', '}', () {
           for (final EnumeratedClass customClass
               in getCodecClasses(api, root)) {
             indent.write('case ${customClass.enumeration}: ');
             indent.writeScoped('', '', () {
               indent.writeln(
                   'return ${customClass.name}.decode(readValue(buffer)!);');
             });
           }
           indent.write('default:');
           indent.writeScoped('', '', () {
             indent.writeln('return super.readValueOfType(type, buffer);');
           });
         });
       });
     }
   });
 }

 /// Creates a Dart type where all type arguments are [Objects].
 String _makeGenericTypeArguments(TypeDeclaration type, String nullTag) {
   return type.typeArguments.isNotEmpty
       ? '${type.baseName}<${type.typeArguments.map<String>((TypeDeclaration e) => 'Object$nullTag').join(', ')}>'
       : _addGenericTypes(type, nullTag);
 }

 /// Creates a `.cast<>` call for an type. Returns an empty string if the
 /// type has no type arguments.
 String _makeGenericCastCall(TypeDeclaration type, String nullTag) {
   return type.typeArguments.isNotEmpty
       ? '.cast<${_flattenTypeArguments(type.typeArguments, nullTag)}>()'
       : '';
 }

 /// Returns an argument name that can be used in a context where it is possible to collide.
 String _getSafeArgumentName(int count, NamedType field) =>
     field.name.isEmpty ? 'arg$count' : 'arg_' + field.name;

 String _getArgumentName(int count, NamedType field) =>
     field.name.isEmpty ? 'arg$count' : field.name;

 String _getMethodArgumentsSignature(
   Method func,
   String Function(int index, NamedType arg) getArgumentName,
   String nullTag,
 ) {
   return func.arguments.isEmpty
       ? ''
       : indexMap(func.arguments, (int index, NamedType arg) {
           final String type = _addGenericTypes(arg.type, nullTag);
           final String argName = getArgumentName(index, arg);
           return '$type $argName';
         }).join(', ');
 }

 void _writeHostApi(DartOptions opt, Indent indent, Api api, Root root) {
   assert(api.location == ApiLocation.host);
   final String codecName = _getCodecName(api);
   _writeCodec(indent, codecName, api, root);
   indent.addln('');
   final String nullTag = opt.isNullSafe ? '?' : '';
   final String unwrapOperator = opt.isNullSafe ? '!' : '';
   bool first = true;
   indent.write('class ${api.name} ');
   indent.scoped('{', '}', () {
     indent.format('''
 /// Constructor for [${api.name}].  The [binaryMessenger] named argument is
 /// available for dependency injection.  If it is left null, the default
 /// BinaryMessenger will be used which routes to the host platform.
 ${api.name}({BinaryMessenger$nullTag binaryMessenger}) : _binaryMessenger = binaryMessenger;

 final BinaryMessenger$nullTag _binaryMessenger;
 ''');

     indent.writeln('static const MessageCodec<Object?> codec = $codecName();');
     indent.addln('');
     for (final Method func in api.methods) {
       if (!first) {
         indent.writeln('');
       } else {
         first = false;
       }
       String argSignature = '';
       String sendArgument = 'null';
       if (func.arguments.isNotEmpty) {
         String argNameFunc(int index, NamedType type) =>
             _getSafeArgumentName(index, type);
         final Iterable<String> argNames = indexMap(func.arguments, argNameFunc);
         sendArgument = '<Object>[${argNames.join(', ')}]';
         argSignature = _getMethodArgumentsSignature(func, argNameFunc, nullTag);
       }
       indent.write(
         'Future<${_addGenericTypes(func.returnType, nullTag)}> ${func.name}($argSignature) async ',
       );
       indent.scoped('{', '}', () {
         final String channelName = makeChannelName(api, func);
         indent.writeln(
             'final BasicMessageChannel<Object$nullTag> channel = BasicMessageChannel<Object$nullTag>(');
         indent.nest(2, () {
           indent.writeln(
             '\'$channelName\', codec, binaryMessenger: _binaryMessenger);',
           );
         });
         final String returnType =
             _makeGenericTypeArguments(func.returnType, nullTag);
         final String castCall = _makeGenericCastCall(func.returnType, nullTag);
         final String returnStatement = func.returnType.isVoid
             ? 'return;'
             : 'return (replyMap[\'${Keys.result}\'] as $returnType$nullTag)$unwrapOperator$castCall;';
         indent.format('''
 final Map<Object$nullTag, Object$nullTag>$nullTag replyMap =\n\t\tawait channel.send($sendArgument) as Map<Object$nullTag, Object$nullTag>$nullTag;
 if (replyMap == null) {
 \tthrow PlatformException(
 \t\tcode: 'channel-error',
 \t\tmessage: 'Unable to establish connection on channel.',
 \t\tdetails: null,
 \t);
 } else if (replyMap['error'] != null) {
 \tfinal Map<Object$nullTag, Object$nullTag> error = (replyMap['${Keys.error}'] as Map<Object$nullTag, Object$nullTag>$nullTag)$unwrapOperator;
 \tthrow PlatformException(
 \t\tcode: (error['${Keys.errorCode}'] as String$nullTag)$unwrapOperator,
 \t\tmessage: error['${Keys.errorMessage}'] as String$nullTag,
 \t\tdetails: error['${Keys.errorDetails}'],
 \t);
 } else {
 \t$returnStatement
 }''');
       });
     }
   });
 }

 void _writeFlutterApi(
   DartOptions opt,
   Indent indent,
   Api api,
   Root root, {
   String Function(Method)? channelNameFunc,
   bool isMockHandler = false,
 }) {
   assert(api.location == ApiLocation.flutter);
   final String codecName = _getCodecName(api);
   _writeCodec(indent, codecName, api, root);
   final String nullTag = opt.isNullSafe ? '?' : '';
   final String unwrapOperator = opt.isNullSafe ? '!' : '';
   indent.write('abstract class ${api.name} ');
   indent.scoped('{', '}', () {
     indent.writeln('static const MessageCodec<Object?> codec = $codecName();');
     indent.addln('');
     for (final Method func in api.methods) {
       final bool isAsync = func.isAsynchronous;
       final String returnType = isAsync
           ? 'Future<${_addGenericTypes(func.returnType, nullTag)}>'
           : _addGenericTypes(func.returnType, nullTag);
       final String argSignature = _getMethodArgumentsSignature(
         func,
         _getArgumentName,
         nullTag,
       );
       indent.writeln('$returnType ${func.name}($argSignature);');
     }
     indent.write('static void setup(${api.name}$nullTag api) ');
     indent.scoped('{', '}', () {
       for (final Method func in api.methods) {
         indent.write('');
         indent.scoped('{', '}', () {
           indent.writeln(
             'const BasicMessageChannel<Object$nullTag> channel = BasicMessageChannel<Object$nullTag>(',
           );
           final String channelName = channelNameFunc == null
               ? makeChannelName(api, func)
               : channelNameFunc(func);
           indent.nest(2, () {
             indent.writeln(
               '\'$channelName\', codec);',
             );
           });
           final String messageHandlerSetter =
               isMockHandler ? 'setMockMessageHandler' : 'setMessageHandler';
           indent.write('if (api == null) ');
           indent.scoped('{', '}', () {
             indent.writeln('channel.$messageHandlerSetter(null);');
           }, addTrailingNewline: false);
           indent.add(' else ');
           indent.scoped('{', '}', () {
             indent.write(
               'channel.$messageHandlerSetter((Object$nullTag message) async ',
             );
             indent.scoped('{', '});', () {
               final String returnType =
                   _addGenericTypes(func.returnType, nullTag);
               final bool isAsync = func.isAsynchronous;
               final String emptyReturnStatement = isMockHandler
                   ? 'return <Object$nullTag, Object$nullTag>{};'
                   : func.returnType.isVoid
                       ? 'return;'
                       : 'return null;';
               String call;
               if (func.arguments.isEmpty) {
                 indent.writeln('// ignore message');
                 call = 'api.${func.name}()';
               } else {
                 indent.writeln(
                   'assert(message != null, \'Argument for $channelName was null.\');',
                 );
                 const String argsArray = 'args';
                 indent.writeln(
                     'final List<Object$nullTag> $argsArray = (message as List<Object$nullTag>$nullTag)$unwrapOperator;');
                 String argNameFunc(int index, NamedType type) =>
                     _getSafeArgumentName(index, type);
                 enumerate(func.arguments, (int count, NamedType arg) {
                   final String argType = _addGenericTypes(arg.type, nullTag);
                   final String argName = argNameFunc(count, arg);
                   indent.writeln(
                       'final $argType$nullTag $argName = $argsArray[$count] as $argType$nullTag;');
                   indent.writeln(
                       'assert($argName != null, \'Argument for $channelName was null, expected non-null $argType.\');');
                 });
                 final Iterable<String> argNames =
                     indexMap(func.arguments, argNameFunc);
                 call =
                     'api.${func.name}(${argNames.map<String>((String x) => '$x$unwrapOperator').join(', ')})';
               }
               if (func.returnType.isVoid) {
                 if (isAsync) {
                   indent.writeln('await $call;');
                 } else {
                   indent.writeln('$call;');
                 }
                 indent.writeln(emptyReturnStatement);
               } else {
                 if (isAsync) {
                   indent.writeln('final $returnType output = await $call;');
                 } else {
                   indent.writeln('final $returnType output = $call;');
                 }
                 const String returnExpression = 'output';
                 final String returnStatement = isMockHandler
                     ? 'return <Object$nullTag, Object$nullTag>{\'${Keys.result}\': $returnExpression};'
                     : 'return $returnExpression;';
                 indent.writeln(returnStatement);
               }
             });
           });
         });
       }
     });
   });
 }

 /// Converts a [List] of [TypeDeclaration]s to a comma separated [String] to be
 /// used in Dart code.
 String _flattenTypeArguments(List<TypeDeclaration> args, String nullTag) {
   return args
       .map<String>((TypeDeclaration arg) => arg.typeArguments.isEmpty
           ? '${arg.baseName}$nullTag'
           : '${arg.baseName}<${_flattenTypeArguments(arg.typeArguments, nullTag)}>$nullTag')
       .join(', ');
 }

 /// Creates the type declaration for use in Dart code from a [NamedType] making sure
 /// that type arguments are used for primitive generic types.
 String _addGenericTypes(TypeDeclaration type, String nullTag) {
   final List<TypeDeclaration> typeArguments = type.typeArguments;
   switch (type.baseName) {
     case 'List':
       return (typeArguments.isEmpty)
           ? 'List<Object$nullTag>'
           : 'List<${_flattenTypeArguments(typeArguments, nullTag)}>';
     case 'Map':
       return (typeArguments.isEmpty)
           ? 'Map<Object$nullTag, Object$nullTag>'
           : 'Map<${_flattenTypeArguments(typeArguments, nullTag)}>';
     default:
       return type.baseName;
   }
 }

 String _addGenericTypesNullable(NamedType field, String nullTag) {
   return '${_addGenericTypes(field.type, nullTag)}$nullTag';
 }

 /// Generates Dart source code for the given AST represented by [root],
 /// outputting the code to [sink].
 void generateDart(DartOptions opt, Root root, StringSink sink) {
   final String nullTag = opt.isNullSafe ? '?' : '';
   final String unwrapOperator = opt.isNullSafe ? '!' : '';
   final List<String> customClassNames =
       root.classes.map((Class x) => x.name).toList();
   final List<String> customEnumNames =
       root.enums.map((Enum x) => x.name).toList();
   final Indent indent = Indent(sink);
   if (opt.copyrightHeader != null) {
     addLines(indent, opt.copyrightHeader!, linePrefix: '// ');
   }
   indent.writeln('// $generatedCodeWarning');
   indent.writeln('// $seeAlsoWarning');
   indent.writeln(
     '// 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',
   );
   indent.writeln('// @dart = ${opt.isNullSafe ? '2.12' : '2.8'}');
   indent.writeln('import \'dart:async\';');
   indent.writeln(
     'import \'dart:typed_data\' show Uint8List, Int32List, Int64List, Float64List;',
   );
   indent.addln('');
   indent.writeln(
       'import \'package:flutter/foundation.dart\' show WriteBuffer, ReadBuffer;');
   indent.writeln('import \'package:flutter/services.dart\';');
   for (final Enum anEnum in root.enums) {
     indent.writeln('');
     indent.write('enum ${anEnum.name} ');
     indent.scoped('{', '}', () {
       for (final String member in anEnum.members) {
         indent.writeln('$member,');
       }
     });
   }
   for (final Class klass in root.classes) {
     indent.writeln('');
     indent.write('class ${klass.name} ');
     indent.scoped('{', '}', () {
       for (final NamedType field in klass.fields) {
         final String datatype = _addGenericTypesNullable(field, nullTag);
         indent.writeln('$datatype ${field.name};');
       }
       if (klass.fields.isNotEmpty) {
         indent.writeln('');
       }
       indent.write('Object encode() ');
       indent.scoped('{', '}', () {
         indent.writeln(
           'final Map<Object$nullTag, Object$nullTag> pigeonMap = <Object$nullTag, Object$nullTag>{};',
         );
         for (final NamedType field in klass.fields) {
           indent.write('pigeonMap[\'${field.name}\'] = ');
           if (customClassNames.contains(field.type.baseName)) {
             indent.addln(
               '${field.name} == null ? null : ${field.name}$unwrapOperator.encode();',
             );
           } else if (customEnumNames.contains(field.type.baseName)) {
             indent.addln(
               '${field.name} == null ? null : ${field.name}$unwrapOperator.index;',
             );
           } else {
             indent.addln('${field.name};');
           }
         }
         indent.writeln('return pigeonMap;');
       });
       indent.writeln('');
       indent.write(
         'static ${klass.name} decode(Object message) ',
       );
       indent.scoped('{', '}', () {
         indent.writeln(
           'final Map<Object$nullTag, Object$nullTag> pigeonMap = message as Map<Object$nullTag, Object$nullTag>;',
         );
         indent.writeln('return ${klass.name}()');
         indent.nest(1, () {
           for (int index = 0; index < klass.fields.length; index += 1) {
             final NamedType field = klass.fields[index];
             indent.write('..${field.name} = ');
             if (customClassNames.contains(field.type.baseName)) {
               indent.format('''
 pigeonMap['${field.name}'] != null
 \t\t? ${field.type.baseName}.decode(pigeonMap['${field.name}']$unwrapOperator)
 \t\t: null''', leadingSpace: false, trailingNewline: false);
             } else if (customEnumNames.contains(field.type.baseName)) {
               indent.format('''
 pigeonMap['${field.name}'] != null
 \t\t? ${field.type.baseName}.values[pigeonMap['${field.name}']$unwrapOperator as int]
 \t\t: null''', leadingSpace: false, trailingNewline: false);
             } else if (field.type.typeArguments.isNotEmpty) {
               final String genericType =
                   _makeGenericTypeArguments(field.type, nullTag);
               final String castCall = _makeGenericCastCall(field.type, nullTag);
               indent.add(
                 '(pigeonMap[\'${field.name}\'] as $genericType$nullTag)$nullTag$castCall',
               );
             } else {
               indent.add(
                 'pigeonMap[\'${field.name}\'] as ${_addGenericTypesNullable(field, nullTag)}',
               );
             }
             indent.addln(index == klass.fields.length - 1 ? ';' : '');
           }
         });
       });
     });
   }
   for (final Api api in root.apis) {
     indent.writeln('');
     if (api.location == ApiLocation.host) {
       _writeHostApi(opt, indent, api, root);
     } else if (api.location == ApiLocation.flutter) {
       _writeFlutterApi(opt, indent, api, root);
     }
   }
 }

 /// Generates Dart source code for test support libraries based on the
 /// given AST represented by [root], outputting the code to [sink].
 void generateTestDart(
   DartOptions opt,
   Root root,
   StringSink sink,
   String mainDartFile,
 ) {
   final Indent indent = Indent(sink);
   if (opt.copyrightHeader != null) {
     addLines(indent, opt.copyrightHeader!, linePrefix: '// ');
   }
   indent.writeln('// $generatedCodeWarning');
   indent.writeln('// $seeAlsoWarning');
   indent.writeln(
     '// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import',
   );
   indent.writeln('// @dart = ${opt.isNullSafe ? '2.12' : '2.8'}');
   indent.writeln('import \'dart:async\';');
   indent.writeln(
     'import \'dart:typed_data\' show Uint8List, Int32List, Int64List, Float64List;',
   );
   indent.writeln(
       'import \'package:flutter/foundation.dart\' show WriteBuffer, ReadBuffer;');
   indent.writeln('import \'package:flutter/services.dart\';');
   indent.writeln('import \'package:flutter_test/flutter_test.dart\';');
   indent.writeln('');
   indent.writeln(
     'import \'${_escapeForDartSingleQuotedString(mainDartFile)}\';',
   );
   for (final Api api in root.apis) {
     if (api.location == ApiLocation.host && api.dartHostTestHandler != null) {
       final Api mockApi = Api(
         name: api.dartHostTestHandler!,
         methods: api.methods,
         location: ApiLocation.flutter,
         dartHostTestHandler: api.dartHostTestHandler,
       );
       indent.writeln('');
       _writeFlutterApi(
         opt,
         indent,
         mockApi,
         root,
         channelNameFunc: (Method func) => makeChannelName(api, func),
         isMockHandler: true,
       );
     }
   }
 }
	// 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.

	import 'ast.dart';
	import 'functional.dart';
	import 'generator_tools.dart';

	/// Options that control how Dart code will be generated.
	class DartOptions {
	/// Constructor for DartOptions.
	const DartOptions({this.isNullSafe = true, this.copyrightHeader});

	/// Determines if the generated code has null safety annotations (Dart >=2.12 required).
	final bool isNullSafe;

	/// A copyright header that will get prepended to generated code.
	final Iterable<String>? copyrightHeader;

	/// Creates a [DartOptions] from a Map representation where:
	/// `x = DartOptions.fromMap(x.toMap())`.
	static DartOptions fromMap(Map<String, Object> map) {
	return DartOptions(
	isNullSafe: map['isNullSafe'] as bool? ?? true,
	copyrightHeader: map['copyrightHeader'] as Iterable<String>?,
	);
	}

	/// Converts a [DartOptions] to a Map representation where:
	/// `x = DartOptions.fromMap(x.toMap())`.
	Map<String, Object> toMap() {
	final Map<String, Object> result = <String, Object>{
	if (isNullSafe != null) 'isNullSafe': isNullSafe,
	if (copyrightHeader != null) 'copyrightHeader': copyrightHeader!,
	};
	return result;
	}

	/// Overrides any non-null parameters from [options] into this to make a new
	/// [DartOptions].
	DartOptions merge(DartOptions options) {
	return DartOptions.fromMap(mergeMaps(toMap(), options.toMap()));
	}
	}

	String _escapeForDartSingleQuotedString(String raw) {
	return raw
	.replaceAll(r'\', r'\\')
	.replaceAll(r'$', r'\$')
	.replaceAll(r"'", r"\'");
	}

	String _getCodecName(Api api) => '_${api.name}Codec';

	void _writeCodec(Indent indent, String codecName, Api api, Root root) {
	indent.write('class $codecName extends StandardMessageCodec ');
	indent.scoped('{', '}', () {
	indent.writeln('const $codecName();');
	if (getCodecClasses(api, root).isNotEmpty) {
	indent.writeln('@override');
	indent.write('void writeValue(WriteBuffer buffer, Object? value) ');
	indent.scoped('{', '}', () {
	for (final EnumeratedClass customClass in getCodecClasses(api, root)) {
	indent.write('if (value is ${customClass.name}) ');
	indent.scoped('{', '} else ', () {
	indent.writeln('buffer.putUint8(${customClass.enumeration});');
	indent.writeln('writeValue(buffer, value.encode());');
	});
	}
	indent.scoped('{', '}', () {
	indent.writeln('super.writeValue(buffer, value);');
	});
	});
	indent.writeln('@override');
	indent.write('Object? readValueOfType(int type, ReadBuffer buffer) ');
	indent.scoped('{', '}', () {
	indent.write('switch (type) ');
	indent.scoped('{', '}', () {
	for (final EnumeratedClass customClass
	in getCodecClasses(api, root)) {
	indent.write('case ${customClass.enumeration}: ');
	indent.writeScoped('', '', () {
	indent.writeln(
	'return ${customClass.name}.decode(readValue(buffer)!);');
	});
	}
	indent.write('default:');
	indent.writeScoped('', '', () {
	indent.writeln('return super.readValueOfType(type, buffer);');
	});
	});
	});
	}
	});
	}

	/// Creates a Dart type where all type arguments are [Objects].
	String _makeGenericTypeArguments(TypeDeclaration type, String nullTag) {
	return type.typeArguments.isNotEmpty
	? '${type.baseName}<${type.typeArguments.map<String>((TypeDeclaration e) => 'Object$nullTag').join(', ')}>'
	: _addGenericTypes(type, nullTag);
	}

	/// Creates a `.cast<>` call for an type. Returns an empty string if the
	/// type has no type arguments.
	String _makeGenericCastCall(TypeDeclaration type, String nullTag) {
	return type.typeArguments.isNotEmpty
	? '.cast<${_flattenTypeArguments(type.typeArguments, nullTag)}>()'
	: '';
	}

	/// Returns an argument name that can be used in a context where it is possible to collide.
	String _getSafeArgumentName(int count, NamedType field) =>
	field.name.isEmpty ? 'arg$count' : 'arg_' + field.name;

	String _getArgumentName(int count, NamedType field) =>
	field.name.isEmpty ? 'arg$count' : field.name;

	String _getMethodArgumentsSignature(
	Method func,
	String Function(int index, NamedType arg) getArgumentName,
	String nullTag,
	) {
	return func.arguments.isEmpty
	? ''
	: indexMap(func.arguments, (int index, NamedType arg) {
	final String type = _addGenericTypes(arg.type, nullTag);
	final String argName = getArgumentName(index, arg);
	return '$type $argName';
	}).join(', ');
	}

	void _writeHostApi(DartOptions opt, Indent indent, Api api, Root root) {
	assert(api.location == ApiLocation.host);
	final String codecName = _getCodecName(api);
	_writeCodec(indent, codecName, api, root);
	indent.addln('');
	final String nullTag = opt.isNullSafe ? '?' : '';
	final String unwrapOperator = opt.isNullSafe ? '!' : '';
	bool first = true;
	indent.write('class ${api.name} ');
	indent.scoped('{', '}', () {
	indent.format('''
	/// Constructor for [${api.name}]. The [binaryMessenger] named argument is
	/// available for dependency injection. If it is left null, the default
	/// BinaryMessenger will be used which routes to the host platform.
	${api.name}({BinaryMessenger$nullTag binaryMessenger}) : _binaryMessenger = binaryMessenger;

	final BinaryMessenger$nullTag _binaryMessenger;
	''');

	indent.writeln('static const MessageCodec<Object?> codec = $codecName();');
	indent.addln('');
	for (final Method func in api.methods) {
	if (!first) {
	indent.writeln('');
	} else {
	first = false;
	}
	String argSignature = '';
	String sendArgument = 'null';
	if (func.arguments.isNotEmpty) {
	String argNameFunc(int index, NamedType type) =>
	_getSafeArgumentName(index, type);
	final Iterable<String> argNames = indexMap(func.arguments, argNameFunc);
	sendArgument = '<Object>[${argNames.join(', ')}]';
	argSignature = _getMethodArgumentsSignature(func, argNameFunc, nullTag);
	}
	indent.write(
	'Future<${_addGenericTypes(func.returnType, nullTag)}> ${func.name}($argSignature) async ',
	);
	indent.scoped('{', '}', () {
	final String channelName = makeChannelName(api, func);
	indent.writeln(
	'final BasicMessageChannel<Object$nullTag> channel = BasicMessageChannel<Object$nullTag>(');
	indent.nest(2, () {
	indent.writeln(
	'\'$channelName\', codec, binaryMessenger: _binaryMessenger);',
	);
	});
	final String returnType =
	_makeGenericTypeArguments(func.returnType, nullTag);
	final String castCall = _makeGenericCastCall(func.returnType, nullTag);
	final String returnStatement = func.returnType.isVoid
	? 'return;'
	: 'return (replyMap[\'${Keys.result}\'] as $returnType$nullTag)$unwrapOperator$castCall;';
	indent.format('''
	final Map<Object$nullTag, Object$nullTag>$nullTag replyMap =\n\t\tawait channel.send($sendArgument) as Map<Object$nullTag, Object$nullTag>$nullTag;
	if (replyMap == null) {
	\tthrow PlatformException(
	\t\tcode: 'channel-error',
	\t\tmessage: 'Unable to establish connection on channel.',
	\t\tdetails: null,
	\t);
	} else if (replyMap['error'] != null) {
	\tfinal Map<Object$nullTag, Object$nullTag> error = (replyMap['${Keys.error}'] as Map<Object$nullTag, Object$nullTag>$nullTag)$unwrapOperator;
	\tthrow PlatformException(
	\t\tcode: (error['${Keys.errorCode}'] as String$nullTag)$unwrapOperator,
	\t\tmessage: error['${Keys.errorMessage}'] as String$nullTag,
	\t\tdetails: error['${Keys.errorDetails}'],
	\t);
	} else {
	\t$returnStatement
	}''');
	});
	}
	});
	}

	void _writeFlutterApi(
	DartOptions opt,
	Indent indent,
	Api api,
	Root root, {
	String Function(Method)? channelNameFunc,
	bool isMockHandler = false,
	}) {
	assert(api.location == ApiLocation.flutter);
	final String codecName = _getCodecName(api);
	_writeCodec(indent, codecName, api, root);
	final String nullTag = opt.isNullSafe ? '?' : '';
	final String unwrapOperator = opt.isNullSafe ? '!' : '';
	indent.write('abstract class ${api.name} ');
	indent.scoped('{', '}', () {
	indent.writeln('static const MessageCodec<Object?> codec = $codecName();');
	indent.addln('');
	for (final Method func in api.methods) {
	final bool isAsync = func.isAsynchronous;
	final String returnType = isAsync
	? 'Future<${_addGenericTypes(func.returnType, nullTag)}>'
	: _addGenericTypes(func.returnType, nullTag);
	final String argSignature = _getMethodArgumentsSignature(
	func,
	_getArgumentName,
	nullTag,
	);
	indent.writeln('$returnType ${func.name}($argSignature);');
	}
	indent.write('static void setup(${api.name}$nullTag api) ');
	indent.scoped('{', '}', () {
	for (final Method func in api.methods) {
	indent.write('');
	indent.scoped('{', '}', () {
	indent.writeln(
	'const BasicMessageChannel<Object$nullTag> channel = BasicMessageChannel<Object$nullTag>(',
	);
	final String channelName = channelNameFunc == null
	? makeChannelName(api, func)
	: channelNameFunc(func);
	indent.nest(2, () {
	indent.writeln(
	'\'$channelName\', codec);',
	);
	});
	final String messageHandlerSetter =
	isMockHandler ? 'setMockMessageHandler' : 'setMessageHandler';
	indent.write('if (api == null) ');
	indent.scoped('{', '}', () {
	indent.writeln('channel.$messageHandlerSetter(null);');
	}, addTrailingNewline: false);
	indent.add(' else ');
	indent.scoped('{', '}', () {
	indent.write(
	'channel.$messageHandlerSetter((Object$nullTag message) async ',
	);
	indent.scoped('{', '});', () {
	final String returnType =
	_addGenericTypes(func.returnType, nullTag);
	final bool isAsync = func.isAsynchronous;
	final String emptyReturnStatement = isMockHandler
	? 'return <Object$nullTag, Object$nullTag>{};'
	: func.returnType.isVoid
	? 'return;'
	: 'return null;';
	String call;
	if (func.arguments.isEmpty) {
	indent.writeln('// ignore message');
	call = 'api.${func.name}()';
	} else {
	indent.writeln(
	'assert(message != null, \'Argument for $channelName was null.\');',
	);
	const String argsArray = 'args';
	indent.writeln(
	'final List<Object$nullTag> $argsArray = (message as List<Object$nullTag>$nullTag)$unwrapOperator;');
	String argNameFunc(int index, NamedType type) =>
	_getSafeArgumentName(index, type);
	enumerate(func.arguments, (int count, NamedType arg) {
	final String argType = _addGenericTypes(arg.type, nullTag);
	final String argName = argNameFunc(count, arg);
	indent.writeln(
	'final $argType$nullTag $argName = $argsArray[$count] as $argType$nullTag;');
	indent.writeln(
	'assert($argName != null, \'Argument for $channelName was null, expected non-null $argType.\');');
	});
	final Iterable<String> argNames =
	indexMap(func.arguments, argNameFunc);
	call =
	'api.${func.name}(${argNames.map<String>((String x) => '$x$unwrapOperator').join(', ')})';
	}
	if (func.returnType.isVoid) {
	if (isAsync) {
	indent.writeln('await $call;');
	} else {
	indent.writeln('$call;');
	}
	indent.writeln(emptyReturnStatement);
	} else {
	if (isAsync) {
	indent.writeln('final $returnType output = await $call;');
	} else {
	indent.writeln('final $returnType output = $call;');
	}
	const String returnExpression = 'output';
	final String returnStatement = isMockHandler
	? 'return <Object$nullTag, Object$nullTag>{\'${Keys.result}\': $returnExpression};'
	: 'return $returnExpression;';
	indent.writeln(returnStatement);
	}
	});
	});
	});
	}
	});
	});
	}

	/// Converts a [List] of [TypeDeclaration]s to a comma separated [String] to be
	/// used in Dart code.
	String _flattenTypeArguments(List<TypeDeclaration> args, String nullTag) {
	return args
	.map<String>((TypeDeclaration arg) => arg.typeArguments.isEmpty
	? '${arg.baseName}$nullTag'
	: '${arg.baseName}<${_flattenTypeArguments(arg.typeArguments, nullTag)}>$nullTag')
	.join(', ');
	}

	/// Creates the type declaration for use in Dart code from a [NamedType] making sure
	/// that type arguments are used for primitive generic types.
	String _addGenericTypes(TypeDeclaration type, String nullTag) {
	final List<TypeDeclaration> typeArguments = type.typeArguments;
	switch (type.baseName) {
	case 'List':
	return (typeArguments.isEmpty)
	? 'List<Object$nullTag>'
	: 'List<${_flattenTypeArguments(typeArguments, nullTag)}>';
	case 'Map':
	return (typeArguments.isEmpty)
	? 'Map<Object$nullTag, Object$nullTag>'
	: 'Map<${_flattenTypeArguments(typeArguments, nullTag)}>';
	default:
	return type.baseName;
	}
	}

	String _addGenericTypesNullable(NamedType field, String nullTag) {
	return '${_addGenericTypes(field.type, nullTag)}$nullTag';
	}

	/// Generates Dart source code for the given AST represented by [root],
	/// outputting the code to [sink].
	void generateDart(DartOptions opt, Root root, StringSink sink) {
	final String nullTag = opt.isNullSafe ? '?' : '';
	final String unwrapOperator = opt.isNullSafe ? '!' : '';
	final List<String> customClassNames =
	root.classes.map((Class x) => x.name).toList();
	final List<String> customEnumNames =
	root.enums.map((Enum x) => x.name).toList();
	final Indent indent = Indent(sink);
	if (opt.copyrightHeader != null) {
	addLines(indent, opt.copyrightHeader!, linePrefix: '// ');
	}
	indent.writeln('// $generatedCodeWarning');
	indent.writeln('// $seeAlsoWarning');
	indent.writeln(
	'// 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',
	);
	indent.writeln('// @dart = ${opt.isNullSafe ? '2.12' : '2.8'}');
	indent.writeln('import \'dart:async\';');
	indent.writeln(
	'import \'dart:typed_data\' show Uint8List, Int32List, Int64List, Float64List;',
	);
	indent.addln('');
	indent.writeln(
	'import \'package:flutter/foundation.dart\' show WriteBuffer, ReadBuffer;');
	indent.writeln('import \'package:flutter/services.dart\';');
	for (final Enum anEnum in root.enums) {
	indent.writeln('');
	indent.write('enum ${anEnum.name} ');
	indent.scoped('{', '}', () {
	for (final String member in anEnum.members) {
	indent.writeln('$member,');
	}
	});
	}
	for (final Class klass in root.classes) {
	indent.writeln('');
	indent.write('class ${klass.name} ');
	indent.scoped('{', '}', () {
	for (final NamedType field in klass.fields) {
	final String datatype = _addGenericTypesNullable(field, nullTag);
	indent.writeln('$datatype ${field.name};');
	}
	if (klass.fields.isNotEmpty) {
	indent.writeln('');
	}
	indent.write('Object encode() ');
	indent.scoped('{', '}', () {
	indent.writeln(
	'final Map<Object$nullTag, Object$nullTag> pigeonMap = <Object$nullTag, Object$nullTag>{};',
	);
	for (final NamedType field in klass.fields) {
	indent.write('pigeonMap[\'${field.name}\'] = ');
	if (customClassNames.contains(field.type.baseName)) {
	indent.addln(
	'${field.name} == null ? null : ${field.name}$unwrapOperator.encode();',
	);
	} else if (customEnumNames.contains(field.type.baseName)) {
	indent.addln(
	'${field.name} == null ? null : ${field.name}$unwrapOperator.index;',
	);
	} else {
	indent.addln('${field.name};');
	}
	}
	indent.writeln('return pigeonMap;');
	});
	indent.writeln('');
	indent.write(
	'static ${klass.name} decode(Object message) ',
	);
	indent.scoped('{', '}', () {
	indent.writeln(
	'final Map<Object$nullTag, Object$nullTag> pigeonMap = message as Map<Object$nullTag, Object$nullTag>;',
	);
	indent.writeln('return ${klass.name}()');
	indent.nest(1, () {
	for (int index = 0; index < klass.fields.length; index += 1) {
	final NamedType field = klass.fields[index];
	indent.write('..${field.name} = ');
	if (customClassNames.contains(field.type.baseName)) {
	indent.format('''
	pigeonMap['${field.name}'] != null
	\t\t? ${field.type.baseName}.decode(pigeonMap['${field.name}']$unwrapOperator)
	\t\t: null''', leadingSpace: false, trailingNewline: false);
	} else if (customEnumNames.contains(field.type.baseName)) {
	indent.format('''
	pigeonMap['${field.name}'] != null
	\t\t? ${field.type.baseName}.values[pigeonMap['${field.name}']$unwrapOperator as int]
	\t\t: null''', leadingSpace: false, trailingNewline: false);
	} else if (field.type.typeArguments.isNotEmpty) {
	final String genericType =
	_makeGenericTypeArguments(field.type, nullTag);
	final String castCall = _makeGenericCastCall(field.type, nullTag);
	indent.add(
	'(pigeonMap[\'${field.name}\'] as $genericType$nullTag)$nullTag$castCall',
	);
	} else {
	indent.add(
	'pigeonMap[\'${field.name}\'] as ${_addGenericTypesNullable(field, nullTag)}',
	);
	}
	indent.addln(index == klass.fields.length - 1 ? ';' : '');
	}
	});
	});
	});
	}
	for (final Api api in root.apis) {
	indent.writeln('');
	if (api.location == ApiLocation.host) {
	_writeHostApi(opt, indent, api, root);
	} else if (api.location == ApiLocation.flutter) {
	_writeFlutterApi(opt, indent, api, root);
	}
	}
	}

	/// Generates Dart source code for test support libraries based on the
	/// given AST represented by [root], outputting the code to [sink].
	void generateTestDart(
	DartOptions opt,
	Root root,
	StringSink sink,
	String mainDartFile,
	) {
	final Indent indent = Indent(sink);
	if (opt.copyrightHeader != null) {
	addLines(indent, opt.copyrightHeader!, linePrefix: '// ');
	}
	indent.writeln('// $generatedCodeWarning');
	indent.writeln('// $seeAlsoWarning');
	indent.writeln(
	'// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import',
	);
	indent.writeln('// @dart = ${opt.isNullSafe ? '2.12' : '2.8'}');
	indent.writeln('import \'dart:async\';');
	indent.writeln(
	'import \'dart:typed_data\' show Uint8List, Int32List, Int64List, Float64List;',
	);
	indent.writeln(
	'import \'package:flutter/foundation.dart\' show WriteBuffer, ReadBuffer;');
	indent.writeln('import \'package:flutter/services.dart\';');
	indent.writeln('import \'package:flutter_test/flutter_test.dart\';');
	indent.writeln('');
	indent.writeln(
	'import \'${_escapeForDartSingleQuotedString(mainDartFile)}\';',
	);
	for (final Api api in root.apis) {
	if (api.location == ApiLocation.host && api.dartHostTestHandler != null) {
	final Api mockApi = Api(
	name: api.dartHostTestHandler!,
	methods: api.methods,
	location: ApiLocation.flutter,
	dartHostTestHandler: api.dartHostTestHandler,
	);
	indent.writeln('');
	_writeFlutterApi(
	opt,
	indent,
	mockApi,
	root,
	channelNameFunc: (Method func) => makeChannelName(api, func),
	isMockHandler: true,
	);
	}
	}
	}