Add a polymer validator: a linter/analysis that will replace the old

pkg/polymer/lib/src/transform/common.dart

Index: pkg/polymer/lib/src/transform/common.dart
diff --git a/pkg/polymer/lib/src/transform/common.dart b/pkg/polymer/lib/src/transform/common.dart
index cad687099e3e36f7a1f5ff16db72146ab1c15637..b0ade96fb2aa33c9b9cca25c9af6605ab6836e7e 100644
--- a/pkg/polymer/lib/src/transform/common.dart
+++ b/pkg/polymer/lib/src/transform/common.dart
@@ -17,7 +17,7 @@ import 'package:source_maps/span.dart' show Span;
  * Parses an HTML file [contents] and returns a DOM-like tree. Adds emitted
  * error/warning to [logger].
  */
-Document parseHtml(String contents, String sourcePath, TransformLogger logger,
+Document _parseHtml(String contents, String sourcePath, TransformLogger logger,
     {bool checkDocType: false}) {
   // TODO(jmesserly): make HTTP encoding configurable
   var parser = new HtmlParser(contents, encoding: 'utf8', generateSpans: true,
@@ -34,6 +34,25 @@ Document parseHtml(String contents, String sourcePath, TransformLogger logger,
   return document;
 }
 
+Future<Document> readPrimaryAsHtml(Transform transform) {
+  var asset = transform.primaryInput;
+  var id = asset.id;
+  return asset.readAsString().then((content) {
+    return _parseHtml(content, id.path, transform.logger,
+      checkDocType: isHtmlInWebOrTest(id));
+  });
+}
+
+Future<Document> readAsHtml(AssetId id, Transform transform) {
+  var primaryId = transform.primaryInput.id;
+  var url = (id.package == primaryId.package) ? id.path
+      : assetUrlFor(id, primaryId, transform.logger);
+  return transform.readInputAsString(id).then((content) {
+    return _parseHtml(content, url, transform.logger,
+      checkDocType: isHtmlInWebOrTest(id));
+  });
+}
+
 /** Create an [AssetId] for a [url] seen in the [source] asset. */
 // TODO(sigmund): delete once this is part of barback (dartbug.com/12610)
 AssetId resolve(AssetId source, String url, TransformLogger logger, Span span) {
@@ -73,6 +92,30 @@ AssetId resolve(AssetId source, String url, TransformLogger logger, Span span) {
   return new AssetId(package, targetPath);
 }
 
-Future<bool> isHtmlInWebOrTest(AssetId id) =>
-    new Future.value(id.extension == '.html' &&
-        (id.path.startsWith('web/') || id.path.startsWith('test/')));
+bool isHtmlInWebOrTest(AssetId id) => id.extension == '.html' &&
+    (id.path.startsWith('web/') || id.path.startsWith('test/'));
+
+/**
+ * Generate the import url for a file described by [id], referenced by a file
+ * with [sourceId].
+ */
+String assetUrlFor(AssetId id, AssetId sourceId, TransformLogger logger) {

[Jennifer Messerly, 2013/09/04 03:13:27]

TODO: this should be in barback, e.g. AssetId.uri or some function like that?
(how do we capture .uriForDart vs .uriForHtml distinction? since the latter does
not support "asset:")

[Siggi Cherem (dart-lang), 2013/09/04 17:57:27]

Done. Added TODO and more comments in bug/12610

+  // use package: and asset: urls if possible
+  if (id.path.startsWith('lib/')) {
+    return 'package:${id.package}/${id.path.substring(4)}';
+  }
+
+  if (id.path.startsWith('asset/')) {
+    return 'asset:${id.package}/${id.path.substring(6)}';

[Jennifer Messerly, 2013/09/04 03:13:27]

Hmm, this won't work if we're in a Dart file?

Does anything support "asset:" yet? Is the idea that html/css support this? It
all seems strange, if we set an image src to "asset:" at runtime that can't
possibly work... Or worse, it would work with dev server and not deployment... I
guess I'm confused about the intent of "asset" but I haven't had any experience
using it, so forgive the newbie questions :)

[Siggi Cherem (dart-lang), 2013/09/04 17:57:27]

Correct. I added more details about this in the bug above. I also added a check
here to ensure we don't run into this problem where we intend to use the url for
dart imports.
Not yet, but soon. I plan to add support for it in our deploy script and in
boot.js.
In dartium/boot.js yes.
My understanding is that our goal is to eventually support it in all these use
cases.

For now, there are only 2 uses of this function in our codebase:
 - get import urls that we'll use in the bootstrap script. These only allow
package: urls, so we won't hit this case of asset: urls (just added some checks
for this)
 - find the url of the source file for reporting errors. The idea is that if you
import an html file from another package, the error message will use a URL that
resolves to that file. 

+  }
+
+  // Use relative urls only if it's possible.
+  if (id.package != sourceId.package) {
+    logger.error("don't know how to import $id from $sourceId");
+    return null;
+  }
+
+  var builder = path.url;
+  return builder.relative(builder.join('/', id.path),
+      from: builder.join('/', builder.dirname(sourceId.path)));
+}