Improve ergonomics around defining importPath in modules

[kevinpschaaf]

Description

When defining elements in ES modules, the library cannot automatically find the import path to set importPath for data-binding use in templates (in HTML Imports the ownerDocument of the template was used to make this automatic). As such, users must manually write a static get importPath getter in their module, with the notion was that they could just return import.meta.url. However, importPath must be a folder URL ending in /, whereas import.meta.url returns a filename.

Ideally the library would accept a filename and take its folder name, or else we could consider accepting the meta object directly (via a differently named getter?) to allow more flexibility in the future.

Versions

• Polymer: v3.x