Cannot upgrade Slate.js past 0.88.1: Copy-paste not working

[bradenmacdonald]

When using any slate version newer than 0.88.1 (e.g. the next version 0.90.0), copy-paste functionality in our editors (Lookup editor, markdown editor) is broken.

The problem seems to be in editor.insertFragment() this line computes the wrong value for inlinePath. Before, it computes [0, 0] but now it computes [] and as a result, the call to splitNodes() splits the parent paragraph into two paragraphs instead of just splitting the text node into two text nodes.

The diff between those two versions of Slate.js is here though I can't easily tell what the problem is, it seems like it's likely related to the new Element.isElement() calls ?

Simple test case: http://junction.local.neolace.net:5555/lookup?e=abcdef

Editor.children is '[{"type":"paragraph","block":true,"children":[{"type":"text","text":"abcdef"}]}]'
On 0.88.1, just the text node gets split into two. On 0.90.0+, the paragraph node gets split into two paragraphs.