Change the URL-space exposed by the browser server.

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index 7d1094edd970080d7e04b8690353efb78633cad2..37f2e6639248a30d20dd15e6d7293f54bd11b286 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -5,11 +5,15 @@
 library test.utils;
 
 import 'dart:async';
+import 'dart:math' as math;
 
+import 'package:crypto/crypto.dart';
 import 'package:path/path.dart' as p;
+import 'package:shelf/shelf.dart' as shelf;
 import 'package:stack_trace/stack_trace.dart';
 
 import 'backend/operating_system.dart';
+import 'util/path_handler.dart';
 
 /// A typedef for a possibly-asynchronous function.
 ///
@@ -179,3 +183,62 @@ Stream mergeStreams(Iterable<Stream> streamIter) {
 
   return controller.stream;
 }
+
+/// Returns a random base64 string containing [bytes] bytes of data.
+///
+/// [seed] is passed to [math.Random]; [urlSafe] and [addLineSeparator] are
+/// passed to [CryptoUtils.bytesToBase64].
+String randomBase64(int bytes, {int seed, bool urlSafe: false,
+    bool addLineSeparator: false}) {
+  var random = new math.Random(seed);
+  var data = [];
+  for (var i = 0; i < bytes; i++) {
+    data.add(random.nextInt(256));
+  }
+  return CryptoUtils.bytesToBase64(data,
+      urlSafe: urlSafe, addLineSeparator: addLineSeparator);
+}
+
+// TODO(nweiz): Remove this and [shelfChange] once Shelf 0.6.0 has been out for
+// six months or so.
+/// Returns `request.url` in a cross-version way.
+///
+/// This follows the semantics of Shelf 0.6.x, even when using Shelf 0.5.x: the
+/// returned URL never starts with "/".
+Uri shelfUrl(shelf.Request request) {
+  var url = request.url;
+  if (!url.path.startsWith("/")) return url;
+  return url.replace(path: url.path.replaceFirst("/", ""));
+}
+
+/// Like [shelf.Request.change], but cross-version.
+///
+/// This follows the semantics of Shelf 0.6.x, even when using Shelf 0.5.x.
+shelf.Request shelfChange(shelf.Request typedRequest, {String path}) {
+  // Explicitly make the request dynamic since we're calling methods here that
+  // aren't defined in all support Shelf versions, and we don't want the
+  // analyzer to complain.
+  var request = typedRequest as dynamic;
+
+  try {
+    return request.change(path: path);
+  } on NoSuchMethodError catch (_) {
+    var newScriptName = p.url.join(request.scriptName, path);
+    if (request.scriptName.isEmpty) newScriptName = "/" + newScriptName;
+
+    var newUrlPath = p.url.relative(request.url.path.replaceFirst("/", ""),
+        from: path);
+    newUrlPath = newUrlPath == "." ? "" : "/" + newUrlPath;
+
+    return request.change(
+        scriptName: newScriptName, url: request.url.replace(path: newUrlPath));
+  }
+}
+
+/// Returns middleware that nests all requests beneath the URL prefix [beneath].
+shelf.Middleware nestingMiddleware(String beneath) {
+  return (handler) {
+    var pathHandler = new PathHandler()..add(beneath, handler);
+    return pathHandler.handler;
+  };
+}