Add a context field to Message in shelf.

Originally https://codereview.chromium.org/226263007/.

BUG=https://code.google.com/p/dart/issues/detail?id=17992
R=kevmoo@google.com

Review URL: https://codereview.chromium.org//239183005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@35102 260f80e4-7a28-3924-810f-c04153c831b5

AUTHORS

@@ -28,4 +28,5 @@ Nikolaus Graf <nik@blossom.io>
 Alexandre Ardhuin <alexandre.ardhuin@gmail.com>
 Victor Berchet <victor.berchet@gmail.com>
 Roel Spilker <r.spilker@gmail.com>
-Martin Charles <martincharles07@gmail.com>
+Martin Charles <martincharles07@gmail.com>
+Anders Holmgren <andersmholmgren@gmail.com>

pkg/shelf/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.5.1
+
+* Add a `context` map to `Request` and `Response` for passing data among
+  handlers and middleware.
+
 ## 0.5.0+1
 
 * Allow `scheduled_test` development dependency up to v0.12.0

pkg/shelf/lib/src/message.dart

@@ -20,6 +20,19 @@ abstract class Message {
   /// The value is immutable.
   final Map<String, String> headers;
 
+  /// Extra context that can be used by for middleware and handlers.
+  ///
+  /// For requests, this is used to pass data to inner middleware and handlers;
+  /// for responses, it's used to pass data to outer middleware and handlers.
+  ///
+  /// Context properties that are used by a particular package should begin with
+  /// that package's name followed by a period. For example, if [logRequests]
+  /// wanted to take a prefix, its property name would be `"shelf.prefix"`,
+  /// since it's in the `shelf` package.
+  ///
+  /// The value is immutable.
+  final Map<String, Object> context;
+
   /// The streaming body of the message.
   ///
   /// This can be read via [read] or [readAsString].
@@ -28,8 +41,11 @@ abstract class Message {
   /// Creates a new [Message].
   ///
   /// If [headers] is `null`, it is treated as empty.
-  Message(this._body, {Map<String, String> headers})
-      : this.headers = _getIgnoreCaseMapView(headers);
+  Message(this._body, {Map<String, String> headers,
+        Map<String, Object> context})
+      : this.headers = _getIgnoreCaseMapView(headers),
+        this.context = new pc.UnmodifiableMapView(
+            context == null ? const {} : new Map.from(context));
 
   /// The contents of the content-length field in [headers].
   ///

pkg/shelf/lib/src/request.dart

@@ -71,14 +71,14 @@ class Request extends Message {
   // TODO(kevmoo) finish documenting the rest of the arguments.
   Request(this.method, Uri requestedUri, {String protocolVersion,
     Map<String, String> headers, Uri url, String scriptName,
-    Stream<List<int>> body})
+    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) {
+            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

pkg/shelf/lib/src/response.dart

@@ -53,8 +53,10 @@ class Response extends Message {
   /// 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})
-      : this(200, body: body, headers: 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.
   ///
@@ -71,8 +73,9 @@ class Response extends Message {
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
   Response.movedPermanently(location, {body, Map<String, String> headers,
-      Encoding encoding})
-      : this._redirect(301, location, body, headers, encoding);
+      Encoding encoding, Map<String, Object> context})
+      : this._redirect(301, location, body, headers, encoding,
+          context: context);
 
   /// Constructs a 302 Found response.
   ///
@@ -89,8 +92,9 @@ class Response extends Message {
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
   Response.found(location, {body, Map<String, String> headers,
-      Encoding encoding})
-      : this._redirect(302, location, body, headers, encoding);
+      Encoding encoding, Map<String, Object> context})
+      : this._redirect(302, location, body, headers, encoding,
+          context: context);
 
   /// Constructs a 303 See Other response.
   ///
@@ -108,17 +112,20 @@ class Response extends Message {
   /// 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})
-      : this._redirect(303, location, body, headers, encoding);
+      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)));
+                headers, 'location', _locationToString(location)),
+            context: context);
 
   /// Constructs a 304 Not Modified response.
   ///
@@ -126,9 +133,11 @@ class Response extends Message {
   /// 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())));
+            headers, 'date', formatHttpDate(new DateTime.now())),
+            context: context);
 
   /// Constructs a 403 Forbidden response.
   ///
@@ -143,8 +152,9 @@ class Response extends Message {
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
   Response.forbidden(body, {Map<String, String> headers,
-      Encoding encoding})
-      : this(403, body: body, headers: headers);
+      Encoding encoding, Map<String, Object> context})
+      : this(403, body: body, headers: headers,
+          context: context);
 
   /// Constructs a 404 Not Found response.
   ///
@@ -159,8 +169,10 @@ class Response extends Message {
   /// 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})
-      : this(404, body: body, headers: headers);
+  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.
   ///
@@ -176,10 +188,11 @@ class Response extends Message {
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
   Response.internalServerError({body, Map<String, String> headers,
-      Encoding encoding})
+      Encoding encoding, Map<String, Object> context})
       : this(500,
             headers: body == null ? _adjust500Headers(headers) : headers,
-            body: body == null ? 'Internal Server Error' : body);
+            body: body == null ? 'Internal Server Error' : body,
+            context: context);
 
   /// Constructs an HTTP response with the given [statusCode].
   ///
@@ -194,9 +207,10 @@ class Response extends Message {
   /// in [headers] will be set appropriately. If there is no existing
   /// Content-Type header, it will be set to "application/octet-stream".
   Response(this.statusCode, {body, Map<String, String> headers,
-      Encoding encoding})
+      Encoding encoding, Map<String, Object> context})
       : super(_bodyToStream(body, encoding),
-          headers: _adjustHeaders(headers, encoding)) {
+          headers: _adjustHeaders(headers, encoding),
+          context: context) {
     if (statusCode < 100) {
       throw new ArgumentError("Invalid status code: $statusCode.");
     }

pkg/shelf/pubspec.yaml

@@ -1,5 +1,5 @@
 name: shelf
-version: 0.5.0+1
+version: 0.5.1-dev
 author: Dart Team <misc@dartlang.org>
 description: Web Server Middleware for Dart
 homepage: http://www.dartlang.org

pkg/shelf/test/message_test.dart

@@ -11,13 +11,15 @@ import 'package:shelf/src/message.dart';
 import 'package:unittest/unittest.dart';
 
 class _TestMessage extends Message {
-  _TestMessage(Map<String, String> headers, Stream<List<int>> body)
-      : super(body, headers: headers);
+  _TestMessage(Map<String, String> headers, Map<String, Object> context,
+        Stream<List<int>> body)
+      : super(body, headers: headers, context: context);
 }
 
-Message _createMessage({Map<String, String> headers, Stream<List<int>> body}) {
+Message _createMessage({Map<String, String> headers,
+    Map<String, Object> context, Stream<List<int>> body}) {
   if (body == null) body = new Stream.fromIterable([]);
-  return new _TestMessage(headers, body);
+  return new _TestMessage(headers, context, body);
 }
 
 void main() {
@@ -43,6 +45,26 @@ void main() {
       expect(() => message.headers['h2'] = 'value2', throwsUnsupportedError);
     });
   });
+
+  group('context', () {
+    test('is accessible', () {
+      var message = _createMessage(context: {'foo': 'bar'});
+      expect(message.context, containsPair('foo', 'bar'));
+    });
+
+    test('null context value becomes empty and immutable', () {
+      var message = _createMessage();
+      expect(message.context, isEmpty);
+      expect(() => message.context['key'] = 'value', throwsUnsupportedError);
+    });
+
+    test('is immutable', () {
+      var message = _createMessage(context: {'key': 'value'});
+      expect(() => message.context['key'] = 'value', throwsUnsupportedError);
+      expect(() => message.context['key2'] = 'value', throwsUnsupportedError);
+    });
+  });
+
   group("readAsString", () {
     test("supports a null body", () {
       var request = _createMessage();