Share a body across all versions of a message.

lib/src/response.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.response;
 
 import 'dart:convert';
 
 import 'package:http_parser/http_parser.dart';
 
@@ skipping 220 matching lines @@
   /// All other context and header values from the [Response] will be included
   /// in the copied [Response] unchanged.
   ///
   /// [body] is the request body. It may be either a [String] or a
   /// [Stream<List<int>>].
   Response change(
       {Map<String, String> headers, Map<String, Object> context, body}) {
     headers = updateMap(this.headers, headers);
     context = updateMap(this.context, context);
 
-    if (body == null) body = this.read();
+    if (body == null) body = getBody(this);
 
     return new Response(this.statusCode, body: body, headers: headers,
         context: context);
   }
 }
 
 /// Adds content-type information to [headers].
 ///
 /// Returns a new map without modifying [headers]. This is used to add
 /// content-type information when creating a 500 response with a default body.
@@ skipping 10 matching lines @@
 /// Converts [location], which may be a [String] or a [Uri], to a [String].
 ///
 /// Throws an [ArgumentError] if [location] isn't a [String] or a [Uri].
 String _locationToString(location) {
   if (location is String) return location;
   if (location is Uri) return location.toString();
 
   throw new ArgumentError('Response location must be a String or Uri, was '
       '"$location".');
 }