pkg/shelf: change helper method on Request and Response

pkg/shelf/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:async';
 import 'dart:convert';
 
 import 'package:http_parser/http_parser.dart';
 
 import 'message.dart';
+import 'util.dart';
 
 /// The response returned by a [Handler].
 class Response extends Message {
   /// The HTTP status code of the response.
   final int statusCode;
 
   /// The date and time after which the response's data should be considered
   /// stale.
   ///
   /// This is parsed from the Expires header in [headers]. If [headers] doesn't
@@ skipping 23 matching lines @@
   /// This indicates that the request has succeeded.
   ///
   /// [body] is the response body. It may be either a [String], a
   /// [Stream<List<int>>], or `null` to indicate no body. If it's a [String],
   /// [encoding] is used to encode it to a [Stream<List<int>>]. It defaults to
   /// UTF-8.
   ///
   /// If [encoding] is passed, the "encoding" field of the Content-Type header
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
-  Response.ok(body, {Map<String, String> headers, Encoding encoding, 
+  Response.ok(body, {Map<String, String> headers, Encoding encoding,
     Map<String, Object> context})
       : this(200, body: body, headers: headers, encoding: encoding,
           context: context);
 
   /// Constructs a 301 Moved Permanently response.
   ///
   /// This indicates that the requested resource has moved permanently to a new
   /// URI. [location] is that URI; it can be either a [String] or a [Uri]. It's
   /// automatically set as the Location header in [headers].
   ///
@@ skipping 44 matching lines @@
   /// If [encoding] is passed, the "encoding" field of the Content-Type header
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
   Response.seeOther(location, {body, Map<String, String> headers,
       Encoding encoding, Map<String, Object> context})
       : this._redirect(303, location, body, headers, encoding,
           context: context);
 
   /// Constructs a helper constructor for redirect responses.
   Response._redirect(int statusCode, location, body,
-      Map<String, String> headers, Encoding encoding, 
+      Map<String, String> headers, Encoding encoding,
       { Map<String, Object> context })
       : this(statusCode,
             body: body,
             encoding: encoding,
             headers: _addHeader(
                 headers, 'location', _locationToString(location)),
             context: context);
 
   /// Constructs a 304 Not Modified response.
   ///
   /// This is used to respond to a conditional GET request that provided
   /// information used to determine whether the requested resource has changed
   /// since the last request. It indicates that the resource has not changed and
   /// the old value should be used.
-  Response.notModified({Map<String, String> headers, 
+  Response.notModified({Map<String, String> headers,
     Map<String, Object> context})
       : this(304, headers: _addHeader(
             headers, 'date', formatHttpDate(new DateTime.now())),
             context: context);
 
   /// Constructs a 403 Forbidden response.
   ///
   /// This indicates that the server is refusing to fulfill the request.
   ///
   /// [body] is the response body. It may be either a [String], a
@@ skipping 15 matching lines @@
   /// requested URI.
   ///
   /// [body] is the response body. It may be either a [String], a
   /// [Stream<List<int>>], or `null` to indicate no body. If it's a [String],
   /// [encoding] is used to encode it to a [Stream<List<int>>]. It defaults to
   /// UTF-8.
   ///
   /// If [encoding] is passed, the "encoding" field of the Content-Type header
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
-  Response.notFound(body, {Map<String, String> headers, Encoding encoding, 
+  Response.notFound(body, {Map<String, String> headers, Encoding encoding,
     Map<String, Object> context})
       : this(404, body: body, headers: headers,
           context: context);
 
   /// Constructs a 500 Internal Server Error response.
   ///
   /// This indicates that the server had an internal error that prevented it
   /// from fulfilling the request.
   ///
   /// [body] is the response body. It may be either a [String], a
@@ skipping 25 matching lines @@
   /// Content-Type header, it will be set to "application/octet-stream".
   Response(this.statusCode, {body, Map<String, String> headers,
       Encoding encoding, Map<String, Object> context})
       : super(_bodyToStream(body, encoding),
           headers: _adjustHeaders(headers, encoding),
           context: context) {
     if (statusCode < 100) {
       throw new ArgumentError("Invalid status code: $statusCode.");
     }
   }
+
+  /// Creates a new [Response] by copying existing values and applying specified
+  /// changes.
+  ///
+  /// New key-value pairs in [context] and [headers] will be added to the copied
+  /// [Response].
+  ///
+  /// If [context] or [headers] includes a key that already exists, the
+  /// key-value pair will replace the corresponding entry in the copied
+  /// [Response].
+  ///
+  /// All other context and header values from the [Response] will be included
+  /// in the copied [Response] unchanged.
+  Response change({Map<String, String> headers, Map<String, Object> context}) {
+    headers = updateMap(this.headers, headers);
+    context = updateMap(this.context, context);
+
+    return new Response(this.statusCode, body: this.read(), headers: headers,
+        context: context);
+  }
 }
 
 /// Converts [body] to a byte stream.
 ///
 /// [body] may be either a [String], a [Stream<List<int>>], or `null`. If it's a
 /// [String], [encoding] will be used to convert it to a [Stream<List<int>>].
 Stream<List<int>> _bodyToStream(body, Encoding encoding) {
   if (encoding == null) encoding = UTF8;
   if (body == null) return new Stream.fromIterable([]);
   if (body is String) return new Stream.fromIterable([encoding.encode(body)]);
@@ skipping 47 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".');
 }