fix duplicate script issue

pkg/polymer/lib/src/build/generated/messages.html

Index: pkg/polymer/lib/src/build/generated/messages.html
diff --git a/pkg/polymer/lib/src/build/generated/messages.html b/pkg/polymer/lib/src/build/generated/messages.html
index 7f324935fb3211fc55353d4f605e06025cf006aa..80e83a9130f41769d3d7442c43f1be71ad7c230e 100644
--- a/pkg/polymer/lib/src/build/generated/messages.html
+++ b/pkg/polymer/lib/src/build/generated/messages.html
@@ -123,12 +123,114 @@ a file that they correspond to. Currently only relative paths can be resolved.</
 
 <div id="code_transformers_2"><h3>Invalid URL to reach another package <a href="#code_transformers_2">#2</a></h3>
 <p>To reach an asset that belongs to another package, use <code>package:</code> URLs in
-Dart code, but in any other language (like HTML or CSS) use relative URLs that
-first go all the way to the <code>packages/</code> directory.</p>
-<p>The rules for correctly writing these imports are subtle and have a lot of
-special cases. Please review
-<a href="https://www.dartlang.org/polymer/app-directories.html">https://www.dartlang.org/polymer/app-directories.html</a> to learn
-more.</p>
+Dart code, but in any other language (like HTML or CSS) use relative URLs.</p>
+<p>These are the rules you must follow to write URLs that refer to files in other

[Siggi Cherem (dart-lang), 2014/10/21 17:06:03]

looks like you might have an old version of code_transformers - this message
should be like the one on the left.

[jakemac, 2014/10/21 18:14:01]

Done.

+packages:</p><ul><li>
+<p>If the file containing the relative URL is an entrypoint under <code>web</code>, use
+<code>packages/package_name/path_to_file</code></p></li><li>
+<p>If the file containing the URL is under <code>web</code>, but in a different directory
+than your entrypoint, walk out to the same level as the entrypoint first,
+then enter the <code>packages</code> directory.</p>
+<p><strong>Note</strong>: If two entrypoints include the file under <code>web</code> containing the
+URL, either both entrypoints have to live in the same directory, or you need
+to move the file to the <code>lib</code> directory.</p></li><li>
+<p>If the file containing the URL lives under <code>lib</code>, walk up as many levels as
+directories you have + 1. This is because code in <code>lib/a/b</code> is loaded from
+<code>packages/package_name/a/b</code>.</p></li></ul>
+<p>The rules are easier to follow if you know how the code is laid out for
+Dartium before you build, and how it is laid out after you build it with <code>pub
+build</code>. Consider the following example:</p>
+<p>   package a</p>
+<pre><code>  lib/
+    |- a1.html
+
+  web/
+    |- a2.html
+</code></pre>
+<p>   package b</p>
+<pre><code>  lib/
+    |- b1.html
+    |- b2/
+        |- b3.html
+</code></pre>
+<p>   package c</p>
+<pre><code>  lib/
+    |- c3.html
+
+  web/
+    |- index.html
+    |- index.dart
+    |- c1/
+        |- c2.html
+</code></pre>
+<p>If your app is package <code>c</code>, then <code>pub get</code> generates a packages directory under
+the web directory, like this:</p>
+<pre><code>  web/
+    |- index.html
+    |- index.dart
+    |- c1/
+    |   |- c2.html
+    |- packages/
+        |- a/
+        |   |- a1.html
+        |- b/
+        |   |- b1.html
+        |   |- b2/
+        |       |- b3.html
+        |- c/
+            |- c3.html
+</code></pre>
+<p>Note that no <code>lib</code> directory is under the <code>packages</code> directory.
+When you launch <code>web/index.html</code> in Dartium, Dartium loads <code>package:</code> imports from
+<code>web/packages/</code>.</p>
+<p>If you need to refer to any file in other packages from <code>index.html</code>, you can
+simply do <code>packages/package_name/path_to_file</code>. For example
+<code>packages/b/b2/b3.html</code>. From <code>index.html</code> you can also refer to files under the
+web directory of the same package using a simple relative URL, like
+<code>c1/c2.html</code>.</p>
+<p>However, if you want to load <code>a1.html</code> from <code>c2.html</code>, you need to reach out to
+the packages directory that lives next to your entrypoint and then load the file
+from there, for example <code>../packages/a/a1.html</code>. Because pub generates symlinks
+to the packages directory also under c1, you may be tempted to write
+<code>packages/a/a1.html</code>, but that is incorrect - it would yield a canonicalization
+error (see more below).</p>
+<p>If you want to load a file from the lib directory of your own package, you
+should also use a package URL. For example, <code>packages/c/c3.html</code> and not
+<code>../lib/c3.html</code>. This will allow you to write code in <code>lib</code> in a way that it
+can be used within and outside your package without making any changes to it.</p>
+<p>Because any time you reach inside a <code>lib/</code> directory you do so using a
+<code>packages/</code> URL, the rules for reaching into other files in other packages are
+always consistent: go up to exit the <code>packages</code> directory and go back inside to
+the file you are looking for.  For example, to reach <code>a1.html</code> from <code>b3.html</code>
+you need to write <code>../../../packages/a/a1.html</code>.</p>
+<p>The motivation behind all these rules is that URLs need to work under many
+scenarios at once:</p><ul><li>
+<p>They need to work in Dartium without any code transformation: resolving the
+path in the context of a simple HTTP server, or using <code>file:///</code> URLs,
+should yield a valid path to assets. The <code>packages</code> directory is safe to use
+because pub already creates it next to entrypoints of your application.</p></li><li>
+<p>They need to be canonical. To take advantage of caching, multiple URLs
+reaching the same asset should resolve to the same absolute URL.</p>
+<p>Also, in projects that use HTML imports (like polymer) tools support that
+you reach a library with either Dart imports or HTML imports, and correctly
+resolve them to be the same library. The rules are designed to allow tools
+to support this.</p>
+<p>For example, consider you have an import might like:</p>
+<pre><code>&lt;link rel=import href=packages/a/a.html&gt;
+</code></pre>
+<p>where a.html has <code>&lt;script type="application/dart" src="a.dart"&gt;</code>. If your
+Dart entrypoint also loads <code>"package:a/a.dart"</code>,  then a tool need to make
+sure that both versions of <code>a.dart</code> are loaded from the same URL. Otherwise,
+you may see errors at runtime like: <code>A is not a subtype of A</code>, which can be
+extremely confusing.</p>
+<p>When you follow the rules above, our tools can detect the pattern in the
+HTML-import URL containing <code>packages/</code> and canonicalize the import
+by converting <code>packages/a/a.dart</code> into <code>package:a/a.dart</code> under the hood.</p></li><li>
+<p>They need to continue to be valid after applications are built.
+Technically this could be done automatically with pub transformers, but to
+make sure that code works also in Dartium with a simple HTTP Server,
+existing transformers do not fix URLs, they just detect inconsistencies and
+produce an error message like this one, instead.</p></li></ul>
 </div><hr />
 
 <div id="code_transformers_3"><h3>Incomplete URL to asset in another package <a href="#code_transformers_3">#3</a></h3>
@@ -137,9 +239,8 @@ more.</p>
 now you must use a canonical URL form for it.</p>
 <p>For example, if <code>packages/a/a.html</code> needs to import <code>packages/b/b.html</code>,
 you might expect a.html to import <code>../b/b.html</code>. Instead, it must import
-<code>../../packages/b/b.html</code>.</p>
-<p>See <a href="http://dartbug.com/15797">issue 15797</a> and
-<a href="https://www.dartlang.org/polymer/app-directories.html">https://www.dartlang.org/polymer/app-directories.html</a> to learn more.</p>
+<code>../../packages/b/b.html</code>.
+See <a href="http://dartbug.com/15797">issue 15797</a>.</p>
 </div><hr /><h2>Messages from package <code>observe</code></h2>
 <hr />
 
@@ -491,10 +592,39 @@ places you probably want to override this behavior to prevent duplicate code.
 To do this, use the following pattern to update your pubspec.yaml:</p>
 <pre><code>transformers:
 - polymer:
-  inline_stylesheets:
-    web/my_file.css: false
+    inline_stylesheets:
+      web/my_file.css: false
 </code></pre>
 <p>If you would like to hide this warning and keep it inlined, do the same thing
 but assign the value to true.</p>
+</div><hr />
+
+<div id="polymer_43"><h3>"dart_support.js" not necessary <a href="#polymer_43">#43</a></h3>
+<p>The script <code>packages/web_components/dart_support.js</code> is still used, but you no
+longer need to put it in your application's entrypoint.</p>
+<p>In the past this file served two purposes:</p><ul><li>to make dart2js work well with the platform polyfills, and</li><li>to support registering Dart APIs for JavaScript custom elements.</li></ul>
+<p>Now, the code from <code>dart_support.js</code> is split in two halves. The half for
+dart2js is now injected by the polymer transformers automatically during <code>pub
+build</code>. The <code>web_components</code> package provides an HTML file containing the other
+half.  Developers of packages that wrap JavaScript custom elements (like
+<code>core_elements</code> and <code>paper_elements</code>) will import that file directly, so
+application developers don't have to worry about it anymore.</p>
+</div><hr />
+
+<div id="polymer_44"><h3>A dart script file was included more than once. <a href="#polymer_44">#44</a></h3>
+<p>Duplicate dart scripts often happen if you have multiple html imports that
+include the same script. The simplest workaround for this is to move your dart
+script to its own html file, and import that instead of the script (html imports
+are automatically deduped).</p>
+<p>For example:</p>
+<pre><code>&lt;script type="application/dart" src="foo.dart"&gt;&lt;/script&gt;
+</code></pre>
+<p>Should turn into:</p>
+<pre><code>&lt;link rel="import" href="foo.html"&gt;
+</code></pre>
+<p>And <code>foo.html</code> should look like:</p>
+<pre><code>&lt;!DOCTYPE html&gt;
+&lt;script type="application/dart" src="foo.dart"&gt;&lt;/script&gt;
+</code></pre>
 </div><hr /></body>
 </html>