Fix newly enforced package:pedantic lints (flutter#123)

- always_declare_return_types
- annotate_overrides
- omit_local_variable_types
- prefer_conditional_assignment
- prefer_single_quotes
- unnecessary_this
- use_function_type_syntax_for_parameters

Author: natebosch

example/example.dart

@@ -5,7 +5,7 @@
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as io;
 
-main() async {
+void main() async {
   var handler = const shelf.Pipeline()
       .addMiddleware(shelf.logRequests())
       .addHandler(_echoRequest);

lib/shelf_io.dart

@@ -41,7 +41,7 @@ export 'src/io_server.dart';
 Future<HttpServer> serve(Handler handler, address, int port,
     {SecurityContext securityContext, int backlog, bool shared = false}) async {
   backlog ??= 0;
-  HttpServer server = await (securityContext == null
+  var server = await (securityContext == null
       ? HttpServer.bind(address, port, backlog: backlog, shared: shared)
       : HttpServer.bindSecure(address, port, securityContext,
           backlog: backlog, shared: shared));
@@ -121,10 +121,10 @@ Future handleRequest(HttpRequest request, Handler handler) async {
   }
 
   var message = StringBuffer()
-    ..writeln("Got a response for hijacked request "
-        "${shelfRequest.method} ${shelfRequest.requestedUri}:")
+    ..writeln('Got a response for hijacked request '
+        '${shelfRequest.method} ${shelfRequest.requestedUri}:')
     ..writeln(response.statusCode);
-  response.headers.forEach((key, value) => message.writeln("$key: $value"));
+  response.headers.forEach((key, value) => message.writeln('$key: $value'));
   throw Exception(message.toString().trim());
 }
 
@@ -140,7 +140,7 @@ Request _fromHttpRequest(HttpRequest request) {
   // Remove the Transfer-Encoding header per the adapter requirements.
   headers.remove(HttpHeaders.transferEncodingHeader);
 
-  void onHijack(void callback(StreamChannel<List<int>> channel)) {
+  void onHijack(void Function(StreamChannel<List<int>>) callback) {
     request.response
         .detachSocket(writeHeaders: false)
         .then((socket) => callback(StreamChannel(socket, socket)));
@@ -155,9 +155,9 @@ Request _fromHttpRequest(HttpRequest request) {
 }
 
 Future _writeResponse(Response response, HttpResponse httpResponse) {
-  if (response.context.containsKey("shelf.io.buffer_output")) {
+  if (response.context.containsKey('shelf.io.buffer_output')) {
     httpResponse.bufferOutput =
-        response.context["shelf.io.buffer_output"] as bool;
+        response.context['shelf.io.buffer_output'] as bool;
   }
 
   httpResponse.statusCode = response.statusCode;
@@ -210,9 +210,9 @@ Future _writeResponse(Response response, HttpResponse httpResponse) {
 Response _logError(Request request, String message, [StackTrace stackTrace]) {
   // Add information about the request itself.
   var buffer = StringBuffer();
-  buffer.write("${request.method} ${request.requestedUri.path}");
+  buffer.write('${request.method} ${request.requestedUri.path}');
   if (request.requestedUri.query.isNotEmpty) {
-    buffer.write("?${request.requestedUri.query}");
+    buffer.write('?${request.requestedUri.query}');
   }
   buffer.writeln();
   buffer.write(message);

lib/src/body.dart

@@ -84,7 +84,7 @@ class Body {
   Stream<List<int>> read() {
     if (_stream == null) {
       throw StateError("The 'read' method can only be called once on a "
-          "shelf.Request/shelf.Response object.");
+          'shelf.Request/shelf.Response object.');
     }
     var stream = _stream;
     _stream = null;

lib/src/cascade.dart

@@ -39,13 +39,13 @@ class Cascade {
   /// considered unacceptable. If [shouldCascade] is passed, responses for which
   /// it returns `true` are considered unacceptable. [statusCodes] and
   /// [shouldCascade] may not both be passed.
-  Cascade({Iterable<int> statusCodes, bool shouldCascade(Response response)})
+  Cascade({Iterable<int> statusCodes, bool Function(Response) shouldCascade})
       : _shouldCascade = _computeShouldCascade(statusCodes, shouldCascade),
         _parent = null,
         _handler = null {
     if (statusCodes != null && shouldCascade != null) {
-      throw ArgumentError("statusCodes and shouldCascade may not both be "
-          "passed.");
+      throw ArgumentError('statusCodes and shouldCascade may not both be '
+          'passed.');
     }
   }
 
@@ -65,7 +65,7 @@ class Cascade {
   Handler get handler {
     if (_handler == null) {
       throw StateError("Can't get a handler for a cascade with no inner "
-          "handlers.");
+          'handlers.');
     }
 
     return (request) {
@@ -81,9 +81,9 @@ class Cascade {
 /// Computes the [Cascade._shouldCascade] function based on the user's
 /// parameters.
 _ShouldCascade _computeShouldCascade(
-    Iterable<int> statusCodes, bool shouldCascade(Response response)) {
+    Iterable<int> statusCodes, bool Function(Response) shouldCascade) {
   if (shouldCascade != null) return shouldCascade;
-  if (statusCodes == null) statusCodes = [404, 405];
+  statusCodes ??= [404, 405];
   statusCodes = statusCodes.toSet();
   return (response) => statusCodes.contains(response.statusCode);
 }

lib/src/hijack_exception.dart

@@ -12,8 +12,9 @@
 class HijackException implements Exception {
   const HijackException();
 
+  @override
   String toString() =>
       "A shelf request's underlying data stream was hijacked.\n"
-      "This exception is used for control flow and should only be handled by a "
-      "Shelf adapter.";
+      'This exception is used for control flow and should only be handled by a '
+      'Shelf adapter.';
 }

lib/src/io_server.dart

@@ -18,21 +18,22 @@ class IOServer implements Server {
   /// Whether [mount] has been called.
   bool _mounted = false;
 
+  @override
   Uri get url {
     if (server.address.isLoopback) {
-      return Uri(scheme: "http", host: "localhost", port: server.port);
+      return Uri(scheme: 'http', host: 'localhost', port: server.port);
     }
 
     // IPv6 addresses in URLs need to be enclosed in square brackets to avoid
     // URL ambiguity with the ":" in the address.
     if (server.address.type == InternetAddressType.IPv6) {
       return Uri(
-          scheme: "http",
-          host: "[${server.address.address}]",
+          scheme: 'http',
+          host: '[${server.address.address}]',
           port: server.port);
     }
 
-    return Uri(scheme: "http", host: server.address.address, port: server.port);
+    return Uri(scheme: 'http', host: server.address.address, port: server.port);
   }
 
   /// Calls [HttpServer.bind] and wraps the result in an [IOServer].
@@ -44,6 +45,7 @@ class IOServer implements Server {
 
   IOServer(this.server);
 
+  @override
   void mount(Handler handler) {
     if (_mounted) {
       throw StateError("Can't mount two handlers for the same server.");
@@ -53,5 +55,6 @@ class IOServer implements Server {
     serveRequests(server, handler);
   }
 
+  @override
   Future close() => server.close();
 }

lib/src/message.dart

@@ -17,7 +17,7 @@ Body getBody(Message message) => message._body;
 /// The default set of headers for a message created with no body and no
 /// explicit headers.
 final _defaultHeaders =
-    ShelfUnmodifiableMap<String>({"content-length": "0"}, ignoreKeyCase: true);
+    ShelfUnmodifiableMap<String>({'content-length': '0'}, ignoreKeyCase: true);
 
 /// Represents logic shared between [Request] and [Response].
 abstract class Message {
@@ -136,8 +136,7 @@ abstract class Message {
   ///
   /// This calls [read] internally, which can only be called once.
   Future<String> readAsString([Encoding encoding]) {
-    if (encoding == null) encoding = this.encoding;
-    if (encoding == null) encoding = utf8;
+    encoding ??= this.encoding ?? utf8;
     return encoding.decodeStream(read());
   }
 

lib/src/middleware.dart

@@ -47,12 +47,11 @@ typedef Middleware = Handler Function(Handler innerHandler);
 /// does it receive [HijackException]s. It can either return a new response or
 /// throw an error.
 Middleware createMiddleware(
-    {FutureOr<Response> requestHandler(Request request),
-    FutureOr<Response> responseHandler(Response response),
-    FutureOr<Response> errorHandler(error, StackTrace stackTrace)}) {
-  if (requestHandler == null) requestHandler = (request) => null;
-
-  if (responseHandler == null) responseHandler = (response) => response;
+    {FutureOr<Response> Function(Request) requestHandler,
+    FutureOr<Response> Function(Response) responseHandler,
+    FutureOr<Response> Function(dynamic error, StackTrace) errorHandler}) {
+  requestHandler ??= (request) => null;
+  responseHandler ??= (response) => response;
 
   void Function(Object, StackTrace) onError;
   if (errorHandler != null) {

lib/src/middleware/logger.dart

@@ -19,9 +19,9 @@ import '../middleware.dart';
 /// The `isError` parameter indicates whether the message is caused by an error.
 ///
 /// If [logger] is not passed, the message is just passed to [print].
-Middleware logRequests({void logger(String msg, bool isError)}) =>
+Middleware logRequests({void Function(String message, bool isError) logger}) =>
     (innerHandler) {
-      if (logger == null) logger = _defaultLogger;
+      logger ??= _defaultLogger;
 
       return (request) {
         var startTime = DateTime.now();

lib/src/request.dart

@@ -134,7 +134,7 @@ class Request extends Message {
       body,
       Encoding encoding,
       Map<String, Object> context,
-      void onHijack(void hijack(StreamChannel<List<int>> channel))})
+      void Function(void Function(StreamChannel<List<int>>)) onHijack})
       : this._(method, requestedUri,
             protocolVersion: protocolVersion,
             headers: headers,
@@ -160,12 +160,11 @@ class Request extends Message {
       Encoding encoding,
       Map<String, Object> context,
       _OnHijack onHijack})
-      : this.requestedUri = requestedUri,
-        this.protocolVersion =
-            protocolVersion == null ? '1.1' : protocolVersion,
-        this.url = _computeUrl(requestedUri, handlerPath, url),
-        this.handlerPath = _computeHandlerPath(requestedUri, handlerPath, url),
-        this._onHijack = onHijack,
+      : requestedUri = requestedUri,
+        protocolVersion = protocolVersion ?? '1.1',
+        url = _computeUrl(requestedUri, handlerPath, url),
+        handlerPath = _computeHandlerPath(requestedUri, handlerPath, url),
+        _onHijack = onHijack,
         super(body, encoding: encoding, headers: headers, context: context) {
     if (method.isEmpty) {
       throw ArgumentError.value(method, 'method', 'cannot be empty.');
@@ -214,6 +213,7 @@ class Request extends Message {
   ///     request = request.change(path: "dir");
   ///     print(request.handlerPath); // => /static/dir/
   ///     print(request.url);        // => file.html
+  @override
   Request change(
       {Map<String, String> headers,
       Map<String, Object> context,
@@ -222,13 +222,13 @@ class Request extends Message {
     headers = updateMap(this.headers, headers);
     context = updateMap(this.context, context);
 
-    if (body == null) body = getBody(this);
+    body ??= getBody(this);
 
     var handlerPath = this.handlerPath;
     if (path != null) handlerPath += path;
 
-    return Request._(this.method, this.requestedUri,
-        protocolVersion: this.protocolVersion,
+    return Request._(method, requestedUri,
+        protocolVersion: protocolVersion,
         headers: headers,
         handlerPath: handlerPath,
         body: body,
@@ -247,7 +247,7 @@ class Request extends Message {
   /// hijacking, such as the `dart:io` adapter. In addition, a given request may
   /// only be hijacked once. [canHijack] can be used to detect whether this
   /// request can be hijacked.
-  void hijack(void callback(StreamChannel<List<int>> channel)) {
+  void hijack(void Function(StreamChannel<List<int>>) callback) {
     if (_onHijack == null) {
       throw StateError("This request can't be hijacked.");
     }
@@ -272,8 +272,8 @@ class _OnHijack {
   /// Calls [this].
   ///
   /// Throws a [StateError] if [this] has already been called.
-  void run(void callback(StreamChannel<List<int>> channel)) {
-    if (called) throw StateError("This request has already been hijacked.");
+  void run(void Function(StreamChannel<List<int>>) callback) {
+    if (called) throw StateError('This request has already been hijacked.');
     called = true;
     newFuture(() => _callback(callback));
   }
@@ -286,8 +286,8 @@ class _OnHijack {
 Uri _computeUrl(Uri requestedUri, String handlerPath, Uri url) {
   if (handlerPath != null &&
       handlerPath != requestedUri.path &&
-      !handlerPath.endsWith("/")) {
-    handlerPath += "/";
+      !handlerPath.endsWith('/')) {
+    handlerPath += '/';
   }
 
   if (url != null) {
@@ -336,8 +336,8 @@ Uri _computeUrl(Uri requestedUri, String handlerPath, Uri url) {
 String _computeHandlerPath(Uri requestedUri, String handlerPath, Uri url) {
   if (handlerPath != null &&
       handlerPath != requestedUri.path &&
-      !handlerPath.endsWith("/")) {
-    handlerPath += "/";
+      !handlerPath.endsWith('/')) {
+    handlerPath += '/';
   }
 
   if (handlerPath != null) {