Replace bootstrap logic with 'boot.js', use 'component/dart' mime-type and add

pkg/polymer/lib/boot.js

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2014, 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.
 
+/// Bootstrap to initialize polymer applications. This library is will be
+/// replaced by boot.dart in the near future (see dartbug.com/18007).
+///
+/// This script contains logic to bootstrap polymer apps during development. It
+/// internally discovers special Dart script tags through HTML imports, and
+/// constructs a new entrypoint for the application that is then launched in an
+/// isolate.
+///
+/// For each script tag found, we will load the corresponding Dart library and
+/// execute all methods annotated with `@initMethod` and register all classes
+/// labeled with `@CustomTag`. We keep track of the order of imports and execute
+/// initializers in the same order.
+///
+/// All polymer applications use this bootstrap logic. It is included
+/// automatically when you include the polymer.html import:
+///
+///    <link rel="import" href="packages/polymer/polymer.html">
+///
+/// There are two important changes compared to previous versions of polymer
+/// (0.10.0-pre.6 and older):
+///
+///   * Use 'component/dart' instead of 'application/dart': Dartium already

[Jennifer Messerly, 2014/04/04 19:26:29]

based on existing mime content types, I'm not sure we can use "component/"
http://www.iana.org/assignments/media-types/media-types.xhtml#application
http://en.wikipedia.org/wiki/Internet_media_type#Type_application

we may need to get it registered, too, depending on choice:
http://www.iana.org/assignments/media-types/application/vnd-dart


based on that we might want to go with something like:

"application/dart;component=1"

since "component=1" is a parameter it doesn't need to be registered. FWIW,
Dartium does not currently recognize it, I tried and it won't execute scripts
with parameters in the content-type.

Here was also the RFC where they recommend parameters over "x-" types:
http://tools.ietf.org/html/rfc6648#page-4

(Parameters would also be a good place to encode the isolate affinity or other
VM startup options, should we ever choose to add them. Other options include
things like "application/dart.component" or "application/dart+component" but I
think those would need to be registered.)

[Siggi Cherem (dart-lang), 2014/04/04 21:09:11]

Interesting - sounds good to me. I switched to application/dart;component=1. We
might have to change that again in the future though. We need to make sure
Dartium will not start loading them (ignoring the parameter)

+///   limits to have a single script tag per document, but it will be changing
+///   semantics soon and make them even stricter. Multiple script tags are not
+///   going to be running on the same isolate after this change. For polymer
+///   applications we'll use a different mime-type on script tags to prevent
+///   Dartium from loading them separately. Instead this bootstrap script
+///   combines those special script tags and creates the application Dartium
+///   needs to run.
+///
+//    If you had:
+///
+///      <polymer-element name="x-foo"> ...
+///      <script type="application/dart" src="x_foo.dart'></script>
+///
+///   Now you need to write:
+///
+///      <polymer-element name="x-foo"> ...
+///      <script type="component/dart" src="x_foo.dart'></script>
+///
+///   * `initPolymer` is gone: we used to initialize applications in two
+///   possible ways: using `init.dart` or invoking initPolymer in your main. Any
+///   of these initialization patterns can be replaced to use an `@initMethod`
+///   instead. For example, If you need to run some initialization code before
+///   any other code is executed, include a "component/dart" script tag that
+///   contains an initializer method with the body of your old main, and make
+///   sure this tag is placed above other html-imports that load the rest of the
+///   application. Initialization methods are executed in the order in which
+///   they are discovered in the HTML document.
 (function() {
-  console.error('"boot.js" is now deprecated. Instead, you can initialize '
-    + 'your polymer application by adding the following tags: \'' +
-    + '<script type="application/dart">export "package:polymer/init.dart";'
-    + '</script><script src="packages/browser/dart.js"></script>\'. '
-    + 'Make sure these script tags come after all HTML imports.');
+  // Only run in Dartium.
+  if (navigator.userAgent.indexOf('(Dart)') === -1) return;
+
+  // Extract a Dart import URL from a script tag, which is the 'src' attribute
+  // of the script tag, or a data-url with the script contents for inlined code.
+  function getScriptUrl(script) {
+    var url = script.src;
+    if (url) {
+      // Normalize package: urls
+      var index = url.indexOf('packages/');
+      if (index == 0 || (index > 0 && url[index - 1] == '/')) {
+        url = "package:" + url.slice(index + 9);
+      }
+      return url;
+    }
+
+    // TODO(sigmund): change back to application/dart: using text/javascript
+    // seems wrong but it hides a warning in Dartium (darbug.com/18000).

[Jennifer Messerly, 2014/04/04 19:39:50]

typo in the darTbug link :)

[Siggi Cherem (dart-lang), 2014/04/04 21:09:11]

:). Done

+    return "data:text/javascript;base64," + window.btoa(script.textContent);

[Jennifer Messerly, 2014/04/04 19:39:50]

WOW. That is beyond crazy!

Does it have to be "text/javascript" to avoid the warning?

[Siggi Cherem (dart-lang), 2014/04/04 21:09:11]

I know, it's pretty weird. I tried a bunch of things (text/plain,
application/vnd-dart, application/postscript, application/xml), but only got JS
and json to work without a warning. Maybe json feels less egregious, so I
switched to that. We could also just keep the warning and live with it until the
bug is fixed.

In playing with this I noticed a bug resolving relative imports, but I don't
think we can fix that so easily, so I filed an issue for it (dartbug.com/18040)

+  }
+
+  // Creates a Dart program that imports [urls] and passes them to
+  // startPolymerInDevelopment, which in turn will invoke methods marked with
+  // @initMethod, and register any custom tag labeled with @CustomTag in those
+  // libraries.
+  function createMain(urls, mainUrl) {
+    var imports = Array(urls.length + 1);
+    for (var i = 0; i < urls.length; ++i) {
+      imports[i] = 'import "' + urls[i] + '" as i' + i + ';';
+    }
+    imports[urls.length] = 'import "package:polymer/src/mirror_loader.dart";';
+    var arg = urls.length == 0 ? '[]' :
+        ('[\n      "' + urls.join('",\n      "') + '"\n     ]');
+    return (imports.join('\n') +
+        '\n\nmain() {\n' +
+        '  startPolymerInDevelopment(' + arg + ');\n' +
+        '}\n');
+  }
+
+  function discoverScripts(content, state) {
+    if (!state) {
+      // internal state tracking documents we've visited, the resulting list of
+      // scripts, and any tags with the incorrect mime-type.
+      state = {seen: {}, scripts: [], badTags: []};
+    }
+    if (!content) return state;
+
+    // Note: we visit both script and link-imports together to ensure we
+    // preserve the order of the script tags as they are discovered.
+    var nodes = content.querySelectorAll('script,link[rel="import"]');
+    for (var i = 0; i < nodes.length; i++) {
+      var node = nodes[i];
+      if (node instanceof HTMLLinkElement) {
+        // TODO(jmesserly): figure out why ".import" fails in content_shell but
+        // works in Dartium.
+        if (node.import && node.import.href) node = node.import;
+
+        if (state.seen[node.href]) continue;
+        state.seen[node.href] = node;
+        discoverScripts(node.import, state);
+      } else if (node instanceof HTMLScriptElement) {
+        if (node.type == 'component/dart') {
+          state.scripts.push(getScriptUrl(node));
+        }
+        if (node.type == 'application/dart') {
+          state.badTags.push(node);
+        }
+      }
+    }
+    return state;
+  }
+
+  window.addEventListener('HTMLImportsLoaded', function (e) {
+    // Append a new script tag that initializes everything.
+    var newScript = document.createElement('script');
+    newScript.type = "application/dart";
+
+    var results = discoverScripts(document);
+    if (results.badTags.length > 0) {
+      console.warn('Dartium currently only allows a single Dart script tag '
+        + 'per application, and in the future it will run them in '
+        + 'separtate isolates.  To prepare for this all the following '
+        + 'script tags need to be updated to use a new mime-type '
+        + '"components/dart" instead of "application/dart":');
+      for (var i = 0; i < results.badTags.length; i++) { 
+        console.warn(results.badTags[i]);
+      }
+
+    }
+    newScript.textContent = createMain(results.scripts);
+    document.body.appendChild(newScript);
+  });
 })();