Fragment's dependency's dependency does not resolve in a correct way

[szalonna]

Context

If I include a sub element in a view fragment, which depends on another component (like px-card), then in the built package subelement's dependency cannot resolve.

Process

1. Create a subelement with a dependency

   <!-- demo-element/demo-element.html -->
   <link rel="import" href="../../bower_components/polymer/polymer.html" />
   <link rel="import" href="../../bower_components/px-card/px-card.html" />
   <dom-module id="demo-element">
   <template>
   <px-card header-text="Header">
     <p>Demo content</p>
   </px-card>
   </template>
   <script>
   </script>
   </dom-module>

2. Create a fragment view which uses the subelement

   <!-- views/demo-view.html -->
   <link rel="import" href="../../bower_components/polymer/polymer.html" />
   <link rel="import" href="../demo-element/demo-element.html" />
   <dom-module id="demo-view">
   <template>
   <div>
     Demo view
     <demo-element></demo-element>
   </div>
   </template>
   <script>
   Polymer({
     is: 'demo-view'
   });
   </script>
   </dom-module>

3. Add the fragment for an app-route
4. Add fragment to the polymer.json
5. Run gulp dist to make a distributable version
6. Start a static file server in the dist/public folder

Expected result

The application up and running in a correct way with no error in the console log.

Current result

The application halts and the following error can be seen in the console:

GET http://localhost:8000/bower_components/px-card/px-card.html 404 (Not Found)

Uncaught DOMException: Failed to execute 'registerElement' on 'Document': Registration failed for type 'dom-module'. A type with that name is already registered.
    at http://localhost:8000/bower_components/polymer/polymer-micro.html:449:10
    at http://localhost:8000/bower_components/polymer/polymer-micro.html:464:2

[szalonna]

It turned out I am facing with an existing Polymer issue: Polymer/polymer#4134

[gstroup]

Yes, I think I came across that same Polymer issue. Glad you tracked it down. If I come up with a solution, I'll let you know.