Circular dependency

[yuqianma]

How to reproduce

• Leaflet version I'm using: v1.2.0
• Browser (with version) I'm using: chrome 63.0.3239.84
• OS/Platform (with version) I'm using: os x

1. Add a log to CRS.Earth.js

console.log(CRS);

1. import crs index

<script type="module">
import * as index from '/node_modules/leaflet/src/geo/crs/index.js';
</script>

What behaviour I'm expecting and which behaviour I'm seeing

CRS should exist. However I got undefined;

Minimal example reproducing the issue

• this example is as simple as possible
• this example does not rely on any third party code

Using http://leafletjs.com/edit.html or any other jsfiddle-like site.

---

Just shift my project to ES Modules. I intend to import modules separately from Leaflet. But got some strange results. After struggled with the error, I finally found it's due to circular dependencies.

For the example above, moving CRS.Earth in crs/index.js to the first item solves the problem.
While since the doc page lists 'Modular build system' as a feature, I am not sure if that is an ideal solution.

Btw, I found this tool is useful: https://github.com/pahen/madge
The result:

Will you deem it a problem? Or should I import the Leaflet.js directly?