Support dart2js in pub serve.

sdk/lib/_internal/pub/lib/src/barback.dart

Index: sdk/lib/_internal/pub/lib/src/barback.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback.dart b/sdk/lib/_internal/pub/lib/src/barback.dart
index 803ec64fb69a049146313b9d4a05aaa3017c63fe..b41c48ad381c9a05bf17e7fbef97f799b67d877b 100644
--- a/sdk/lib/_internal/pub/lib/src/barback.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback.dart
@@ -7,7 +7,10 @@ library pub.barback;
 import 'dart:async';
 
 import 'package:barback/barback.dart';
+import 'package:path/path.dart' as path;
 
+import 'barback/dart_forwarding_transformer.dart';
+import 'barback/dart2js_transformer.dart';
 import 'barback/load_all_transformers.dart';
 import 'barback/pub_package_provider.dart';
 import 'barback/server.dart';
@@ -54,6 +57,12 @@ class TransformerId {
 Future<BarbackServer> createServer(String host, int port, PackageGraph graph) {
   var provider = new PubPackageProvider(graph);
   var barback = new Barback(provider);
+
+  var builtInTransformers = [

[nweiz, 2013/09/27 22:21:17]

Add a TODO here to add a dart2dart transformer and a way of choosing to simulate
production mode.

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+    new Dart2JSTransformer(graph),
+    new DartForwardingTransformer()
+  ];
+
   return BarbackServer.bind(host, port, barback, graph.entrypoint.root.name)
       .then((server) {
     watchSources(graph, barback);
@@ -75,7 +84,7 @@ Future<BarbackServer> createServer(String host, int port, PackageGraph graph) {
       })
     ];
 
-    loadAllTransformers(server, graph).then((_) {
+    loadAllTransformers(server, graph, builtInTransformers).then((_) {
       if (!completer.isCompleted) completer.complete(server);
     }).catchError((error) {
       if (!completer.isCompleted) completer.completeError(error);
@@ -141,3 +150,56 @@ Uri idToPackageUri(AssetId id) {
 
   return new Uri(scheme: 'package', path: id.path.replaceFirst('lib/', ''));
 }
+
+/// Converts a [uri] served by pub serve into an [AssetId] that can be

[nweiz, 2013/09/27 22:21:17]

"uri" -> "url", throughout this function (except the type of the parameter).

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+/// requested from barback.
+AssetId uriToId(String rootPackage, Uri uri) {

[nweiz, 2013/09/27 22:21:17]

It feels like this should be a method on [BarbackServer]. The server knows its
root package, and it feels weird to have [uri] here without an explicit context
for what server it refers to.

This will also let you assert that the hostname of [uri] (if one exists) matches
the server's.

[Bob Nystrom, 2013/09/28 00:56:11]

Done.
Didn't do this. This is called in the request handler for the server, so
checking the hostname feels redundant.

+  var parts = path.url.split(uri.path);
+
+  // Strip the leading "/" from the URL.
+  parts.removeAt(0);
+
+  try {
+    var id = specialPathToId(parts);
+    if (id != null) return id;
+  } on FormatException catch(_) {

[nweiz, 2013/09/27 22:21:17]

Style nit: "catch (_)"

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+    // If we got here, we had a path like "/packages" which is a special
+    // directory, but not a valid path since it lacks a following package name.
+    return null;

[nweiz, 2013/09/27 22:21:17]

It feels like throwing an error for an invalid URI makes sense here.

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+  }
+
+  // Otherwise, it's a path in current package's web directory.
+  var relativePath = path.url.join("web", path.url.joinAll(parts));
+  return new AssetId(rootPackage, relativePath);
+}
+
+/// Converts [parts], a list of path components into an [AssetId] if [parts]

[nweiz, 2013/09/27 22:21:17]

"components" -> "components,"

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+/// is from a path containing "packages" or "assets".
+///
+/// If the path doesn't contain one of those special directories, returns null.
+/// If it does contain a special directory, but lacks a following package name,
+/// throws a [FormatException].
+AssetId specialPathToId(List<String> parts) {

[nweiz, 2013/09/27 22:21:17]

As a public API function of this library, it doesn't feel right that this takes
a list of parts. I'd make it just take a relative path instead. An occasional
extra join+split is worth the API cleanliness.

[Bob Nystrom, 2013/09/28 00:56:11]

The problem is that this can be called with both URLs and file paths, so it's
ambiguous as to how to properly separate it. So I just rely on the caller to do
that instead.

[nweiz, 2013/09/30 17:33:34]

That's easy to change by delaying the URI-to-path conversion of the
[resourceUri] argument to [BarbackSourceFileProvider.readStringFromUri]. If you
leave it as a URI when it's passed to [_sourcePathToId], you can pass in the
URI's path component to this function.

[Bob Nystrom, 2013/10/01 19:08:55]

Done.

+  for (var pair in [["packages", "lib"], ["assets", "asset"]]) {
+    var partName = pair[0];
+    var dirName = pair[1];

[nweiz, 2013/09/27 22:21:17]

Style nit: I like using [Iterable.first] and [Iterable.last] when dealing with a
list that's known to be two elements.

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+
+    // Find the package name and the relative path in the package.
+    var index = parts.indexOf(partName);
+    if (index == -1) continue;
+
+    // If we got here, the path *did* contain the special directory, which
+    // means we should not interpret it as a regular path, even if it's
+    // missing the package name after it, which makes it invalid here.

[nweiz, 2013/09/27 22:21:17]

Nit: "as a regular path. If it's missing the package name after the special
directory, it's invalid."

I know I wrote this in the first place, but I like the new phrasing better :p.

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+    if (index + 1 >= parts.length) {
+      throw new FormatException('Expected package named after "$partName".');

[nweiz, 2013/09/27 22:21:17]

"named" -> "name"

I would include more context here. Something like "Invalid package path
$whatever: ...".

[Bob Nystrom, 2013/09/28 00:56:11]

Done.

+    }
+
+    var package = parts[index + 1];
+    var assetPath = path.url.join(dirName,
+        path.url.joinAll(parts.skip(index + 2)));
+    return new AssetId(package, assetPath);
+  }
+
+  return null;
+}