Does <link> order matter?

[secretrobotron]

We've been using Polymer in our app for a while before .2, and the ordering of <link>s hadn't mattered. Now, I'm seeing inheritance (extends="...") fail when link tags are out of order.

[sorvell]

Yes, import order matters. Yes, this changed slightly recently.

Just to be clear, if x-foo is defined in x-foo.html, and x-bar extends x-foo and is defined in x-bar.html, then x-foo.html must be imported before x-bar.html.

Until recently, polymer would wait to upgrade x-bar until x-foo was available. We decided to remove this feature, but we still issue a warning on the console in this case. We removed the feature because it's only a half measure: it handles extension but not composition. Consider, for example, composition. If x-bar creates an x-zot inside its shadowRoot. In this case x-zot must also be ordered before x-bar.

[secretrobotron]

Ok, excellent! Did I miss that in the docs somewhere?

We can manually order our link tags so that loading happens correctly, but is there a suggested loading mechanism that would make it easier (since we were relying on HTMLImports to do the work before)?

[sorvell]

You'll need to do this manually, but it should be pretty straightforward and easy. The convention we're using is that an import defines a custom element. That import would then import any other element imports that it needs. This what you only have to ever consider the imports needed for a given element. For example, xbar.html:

<link rel="import" href="../components/x-foo/x-foo.html">
<polymer-element name="x-bar" extends="x-bar">
  ...
</polymer-element>

We also have a tool called vulcanize (https://github.com/Polymer/vulcanize) that creates builds of imports.

@ebidel Is this doc'd and if not, can we be sure to add it? Thanks.

[secretrobotron]

That's perfect, actually. If 2 links import the same file, it's only processed once, correct?

[sorvell]

Yes, that's correct. HTMLImports have built-in de-duping.

On Fri, Feb 21, 2014 at 12:42 PM, Bobby Richter [email protected]:

That's perfect, actually. If 2 links import the same file, it's only
processed once, correct?

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/429#issuecomment-35771369
.

[secretrobotron]

Hooray! Thanks!

[ebidel]

I wrote an extensive article on using HTML Imports for dependencies,
performance, and de-duping:
http://www.html5rocks.com/en/tutorials/webcomponents/imports/

On the Polymer front, Addy wrote a great article on our Vulcanize tool:
http://www.polymer-project.org/articles/concatenating-web-components.html

On Fri, Feb 21, 2014 at 12:55 PM, Bobby Richter [email protected]:

Hooray! Thanks!

Reply to this email directly or view it on GitHubhttps://github.com//issues/429#issuecomment-35772584
.

[sorvell]

That's awesome. Thanks @ebidel!

[ebidel]

There's also a discussion loading import as deps in "creating elements":
http://www.polymer-project.org/docs/start/creatingelements.html#reuse

Closing this since there's no followup AI.