Introduce transformers for:

lib/src/transform/code_extractor.dart

+// Copyright (c) 2013, 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.
+
+/** Transfomer that extracts inlined script code into separate assets. */
+library polymer.src.transformers;
+
+import 'dart:async';
+
+import 'package:path/path.dart' as path;

[Jennifer Messerly, 2013/08/19 22:57:26]

not sure if you want to sort these, noticed a few places they aren't. doesn't
matter to me FWIW

[Siggi Cherem (dart-lang), 2013/08/21 20:35:42]

Done.

+import 'package:barback/barback.dart';
+import 'common.dart';
+
+/**
+ * Transformer that extracts Dart code inlined in HTML script tags and outputs a
+ * separate file for each.
+ */
+class InlineCodeExtractor extends Transformer {

[terry, 2013/08/20 17:03:24]

Does Barback has the ability to pass options for things like strict mode, etc.

[Bob Nystrom, 2013/08/20 17:20:05]

No, it doesn't currently have a way to handle configuration. (Or another way of
looking at it is it expects the transformers you give it to already be
configured.) It's on the roadmap.

+  Future<bool> isPrimary(Asset input) =>
+      new Future.value(input.id.extension == ".html");
+
+  Future apply(Transform transform) {
+    var inputId = transform.primaryId;
+    return getPrimaryContent(transform).then((content) {

[Bob Nystrom, 2013/08/19 22:28:59]

Add a TODO mentioning #12515 or #12516 here since barback should make this
easier.

[Siggi Cherem (dart-lang), 2013/08/21 20:35:42]

awesome. Done. moved the TODOs to the definition of these functions.

+      var document = parseHtml(content, inputId.path, transform.logger);
+      int count = 0;
+      for (var tag in document.queryAll('script')) {
+        if (tag.attributes['type'] == 'application/dart' &&
+            !tag.attributes.containsKey('src')) {
+          // TODO(sigmund): should we automatically include a library directive
+          // if it doesn't have one?
+          var filename = path.basename(inputId.path);
+          tag.attributes['src'] = '$filename.$count.dart';
+          var textContent = tag.nodes.first;
+          var id = inputId.addExtension('.$count.dart');

[Jennifer Messerly, 2013/08/19 22:57:26]

do we need to worry about this name conflicting with an existing file? or does
barback handle this?

[Siggi Cherem (dart-lang), 2013/08/21 20:35:42]

It's mainly on our hands to worry about finding a unique asset id in these
cases.

Barback helps in that collisions are not overriding files in the file system,
but we have to be careful not choose something that already exists. This current
scheme in this code assumes that users are not calling their files
foo.html.0.dart.

Bob - would it make sense to provide something extra in barback to guarantee
uniqueness, for example a transformer or phase identifier that can be added to
the asset id?

[Bob Nystrom, 2013/08/21 21:18:21]

Similarly, you need to choose something that is not the output of a sibling
transformer. You can collide with generated stuff too.
I don't think we want to add more state to AssetID, but it might be good to have
an API that will generate a fresh unique-ish ID for you. I'm not sure exactly
what that would look like, though. Want to just sit on this for now and see if
it becomes a problem?

+          transform.addOutput(new Asset.fromString(id, textContent.value));

[terry, 2013/08/20 17:03:24]

Can barback produce an output stream.  Might want the ability to produce a file
name for referring in other files or an optional filename filter to produce a
file name of a particular extension

[Bob Nystrom, 2013/08/20 17:20:05]

Yes, a barback Asset exposes a stream interface you can use to read its
contents.
Assets also have file paths, even though they may not be physically on the file
system.

+          textContent.remove();
+          count++;
+        }
+      }
+      transform.addOutput(new Asset.fromString(inputId,
+            count == 0 ? content : document.outerHtml));

[Bob Nystrom, 2013/08/19 22:28:59]

Just indent +4 here or all the way to the "(".

[Siggi Cherem (dart-lang), 2013/08/21 20:35:42]

Done. Thanks, vi-mode for Dart is not perfect yet =)

+    });
+  }
+}