pkg/shelf: change helper method on Request and Response

pkg/shelf/lib/src/request.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library shelf.request;
 
 import 'dart:async';
 
 import 'package:http_parser/http_parser.dart';
 
@@ skipping 63 matching lines @@
     Stream<List<int>> body, Map<String, Object> context})
       : this.requestedUri = requestedUri,
         this.protocolVersion = protocolVersion == null ?
             '1.1' : protocolVersion,
         this.url = _computeUrl(requestedUri, url, scriptName),
         this.scriptName = _computeScriptName(requestedUri, url, scriptName),
         super(body == null ? new Stream.fromIterable([]) : body,
             headers: headers, context: context) {
     if (method.isEmpty) throw new ArgumentError('method cannot be empty.');
 
-    // TODO(kevmoo) use isAbsolute property on Uri once Issue 18053 is fixed
-    if (requestedUri.scheme.isEmpty) {
+    if (!requestedUri.isAbsolute) {
       throw new ArgumentError('requstedUri must be an absolute URI.');
     }
 
     if (this.scriptName.isNotEmpty && !this.scriptName.startsWith('/')) {
       throw new ArgumentError('scriptName must be empty or start with "/".');
     }
 
     if (this.scriptName == '/') {
       throw new ArgumentError(
           'scriptName can never be "/". It should be empty instead.');
     }
 
     if (this.scriptName.endsWith('/')) {
       throw new ArgumentError('scriptName must not end with "/".');
     }
 
     if (this.url.path.isNotEmpty && !this.url.path.startsWith('/')) {
       throw new ArgumentError('url must be empty or start with "/".');
     }
 
     if (this.scriptName.isEmpty && this.url.path.isEmpty) {
       throw new ArgumentError('scriptName and url cannot both be empty.');
     }
   }
+
+  /// Creates a new [Request] by copying existing values and applying specified
+  /// changes.
+  ///
+  /// New key-value pairs in [context] and [headers] will be added to the copied
+  /// [Request].
+  ///
+  /// If [context] or [headers] includes a key that already exists, the
+  /// key-value pair will replace the corresponding entry in the copied
+  /// [Request].
+  ///
+  /// All other context and header values from the [Request] will be included
+  /// in the copied [Request] unchanged.
+  Request change({Map<String, String> headers, Map<String, Object> context}) {
+    headers = updateMap(this.headers, headers);
+    context = updateMap(this.context, context);
+
+    return new Request(this.method, this.requestedUri,
+        protocolVersion: this.protocolVersion, headers: headers, url: this.url,
+        scriptName: this.scriptName, body: this.read(), context: context);
+  }
 }
 
 /// Computes `url` from the provided [Request] constructor arguments.
 ///
 /// If [url] and [scriptName] are `null`, infer value from [requestedUrl],
 /// otherwise return [url].
 ///
 /// If [url] is provided, but [scriptName] is omitted, throws an
 /// [ArgumentError].
 Uri _computeUrl(Uri requestedUri, Uri url, String scriptName) {
@@ skipping 24 matching lines @@
     return '';
   }
 
   if (url != null && scriptName != null) {
     return scriptName;
   }
 
   throw new ArgumentError(
       'url and scriptName must both be null or both be set.');
 }