Check the state of the HTTP request and response when handling headers

tests/standalone/src/io/HttpHeadersState.dart

+// Copyright (c) 2012, 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.
+//
+
+#import("dart:isolate");
+#import("dart:io");
+
+void test(int totalConnections, [String body]) {
+  HttpServer server = new HttpServer();
+  server.onError = (e) => Expect.fail("Unexpected error $e");
+  server.listen("127.0.0.1", 0, totalConnections);
+  server.defaultRequestHandler = (HttpRequest request, HttpResponse response) {
+    // Cannot mutate request headers.
+    Expect.throws(() => request.headers.add("X-Request-Header", "value"),
+                  (e) => e is HttpException);
+    Expect.equals("value", request.headers.value("X-Request-Header"));
+    OutputStream stream = response.outputStream;
+    // Can still mutate response headers as long as no data has been sent.
+    response.headers.add("X-Response-Header", "value");
+    if (body != null) {
+      stream.writeString(body);
+      // Cannot mutate response headers when data has been sent.
+      Expect.throws(() => request.headers.add("X-Request-Header", "value2"),
+                    (e) => e is HttpException);
+    }
+    stream.close();
+    // Cannot mutate response headers when data has been sent.
+    Expect.throws(() => request.headers.add("X-Request-Header", "value3"),
+                  (e) => e is HttpException);
+  };
+
+  int count = 0;
+  HttpClient client = new HttpClient();
+  for (int i = 0; i < totalConnections; i++) {
+    HttpClientConnection conn = client.get("127.0.0.1", server.port, "/");
+    conn.onError = (e) => Expect.fail("Unexpected error $e");
+    conn.onRequest = (HttpClientRequest request) {
+      if (body != null) {
+        request.contentLength = -1;
+      }
+      OutputStream stream = request.outputStream;
+      // Can still mutate request headers as long as no data has been sent.
+      request.headers.add("X-Request-Header", "value");
+      if (body != null) {
+        stream.writeString(body);
+        // Cannot mutate request headers when data has been sent.
+        Expect.throws(() => request.headers.add("X-Request-Header", "value2"),
+                      (e) => e is HttpException);
+      }
+      stream.close();
+      // Cannot mutate request headers when data has been sent.
+      Expect.throws(() => request.headers.add("X-Request-Header", "value3"),
+                    (e) => e is HttpException);
+    };
+    conn.onResponse = (HttpClientResponse response) {
+      // Cannot mutate response headers.
+      Expect.throws(() => response.headers.add("X-Response-Header", "value"),
+                   (e) => e is HttpException);
+      Expect.equals("value", response.headers.value("X-Response-Header"));
+      count++;
+      if (count == totalConnections) {
+        client.shutdown();
+        server.close();
+      }
+    };
+  }
+}
+
+void main() {
+  test(5);
+  test(5, "Hello and goodbye");
+}