switch to plain JSON models

[ianstormtaylor]

Do you want to request a feature or report a bug?

Improvement.

What's the current behavior?

This is an issue summarizing the discussion in #2345. I'm opening it so that we can track some of the dependent issues that need to be solved before we can fully migrate, since there are some things left to be figured out...

slate

• Change memoization to not use instances. (Use weakmap to prevent memory leak and remove indirect __cache__key #2471, thanks @zhujinxuan!)
• Change slate core to use paths or path refs, not keys. (remove all key usage from Slate's core #2864)
• Remove extraneous instance methods. (remove model-level mutation methods #2711)
• Remove the *ByKey commands. (remove the *ByKey commands #2858)
• Deprecate instance methods in favor of static methods.

slate-react

• Pass a pathRef/pathQuery object to components, not keys. (introduce a "refs" concept #2413)
• Change findDOMNode/etc. to use refs instead of searching by key. (change findDOMNode to use a React ref tree #2716)
• Change decorations to use relative paths, and always set them. (split up marks, decorations, and annotations #2745)
• Change handlers to use findPath instead of findNode().key. (add a findPath DOM helper #2717)
• Augment the React plugin to set keys on nodes, and when operations are applied.

After all of those are landed, we can then have a single breaking change where we change everything to use plain JSON objects instead Immutable.js instances, since none of the internals are relying on the instances anymore.

[ianstormtaylor]

Fixed by #3093.