This comment was originally written by aforsel...@gmail.com

The following error can be seen in the Chrome console window:
"
flushing 29 elements
Uncaught TypeError: Cannot read property 'element' of undefined 127.0.0.1:3030/chessboard.dart/build/example/app.html_bootstrap.dart.js:1509
"

Removed Priority-Unassigned label.
Added Priority-High, Area-Pkg, Pkg-Polymer, Triaged labels.

Seems like a bug in the polymer.js logic here:

https://github.com/Polymer/polymer-dev/blob/b93ff1fda0e770a10f16d55647da79f3f7aedf18/src/declaration/prototype.js#L208

I'll try to create a small test case for them, but I was able to validate that just changing

  if (p.element)

to:

  if (p && p.element)

fixes the issue.

I'll create a change for them and keep you posted.

meanwhile, if you need to make progress, you can edit your local copy of polymer.html to load polymer.concat.js, and change polymer.concat.js with the patch above.

Added Started label.

This comment was originally written by @kaendfinger

I have this issue as well. Any chance it will be done tonight? This big has set me back quite a bit today :P

I've been looking more into it, and I can't reproduce it on Javascript alone. The polymer code works if the name of the base class is 'null' rather than 'undefined'.

It looks like the issue is in our dart:js layer. dart:js is assuming that null values are 'undefined' in Javascript, but in this case, we need to actually use 'null'.

Indeed - it's a bug from dart:js. See issue #20305.

I'll send a patch for dart:js shortly, but that wont be available until the next build of the -dev channel of the SDK

The fix is now submitted in r38814. As soon as the next dev build is released this should work again.

Meanwhile, one way to work around this is to edit your copy of polymer.js under packages/polymer/src/js/polymer/polymer.js and change this portion:
  b.element?this.findTypeExtension(b.element.extends)

to:
  b&&b.element?this.findTypeExtension(b.element.extends)

Added Duplicate label.
Marked as being merged into #20305.

Another way to fix this is to edit the output of pub-build. The app_bootstrap.dart.js will have a portion like this:

  if(a==null)return
  else if(typeof a==="string"||typeof a==="number"||typeof a==="boolean")return a

Changing it to add null at the end of the first line should fix the issue for you:

  if(a==null)return null
  else if(typeof a==="string"||typeof a==="number"||typeof a==="boolean")return a

This comment was originally written by likunarms...@gmail.com

I'm having the same problem and I don't find any code portion looks like that.

When shall we expect the next dev channel release? Both this issue and issue of pub version conflict with Polymer should be addressed soon

the bots finished building the next release, I expect it will be released after some testing early next week.

This comment was originally written by dave...@gmail.com

Siggi's suggestion in #­7 let me build so it runs in Chrome, but it remains broken in Safari with: http://d.pr/i/I3Lz See http://mycommunity.org for a live example (running on GCE by the way!).

This comment was originally written by daveno...@gmail.com

Confirming that the suggestion in #­8 had the same effect: works in Chrome, does not work in Safari:

[Error] Element name could not be inferred.
    b (polymer.js, line 12)
    (anonymous function) (mycommunity.org, line 4950)

Hey Dave, cool to see the live example! :) - It sounds like the issue you see in Safari is something unrelated though. I've opened a separate bug to track that here: https://code.google.com/p/dart/issues/detail?id=20354

If you have an example we can build locally that runs into the error, could you please post it there?

Thanks!

This comment was originally written by dave...@gmail.com

Hi Siggi. Pull and checkout the Dev branch at
http://github.com/DaveNotik/dart-stack, create a lib/config/config.dart
using the example in that same dir (the directory should be build/web), pub
build, and "dart start.dart" to start the server. Looking forward to any
guidance!

This issue has been moved to dart-archive/polymer-dart#254.