JSON.parse?

Looks great overall! Love where this is going.
A lot of my comments actually have to do with the docs not being consistent with standards. I've marked those. Also have comments about testing.

The unit testing could use more fleshing out. I know we have existing tests for the built-in fields, but we really should have tests for all the new registration support and the options for each field to ensure that the base foundation is working correctly. I know that's a lot more work, but it'll be worth it.

"JavaScript"
Here and all the others.

Description is intended 1 space too far.

This kinda reads weird. Maybe:
The way that the review request should be closed. This can be one of <values>.

This is only used if ``fieldName`` is ``closeDescription``.

So this broke when originally converted to ES6. The newline shouldn't have been there, as that adds unwanted whitespace to be beginning. Mind fixing it while you're here? <%- describeText %> should be flush up against the prior <label>.

Same here. There shouldn't be any newline involved.

You can pass this.showBanner in directly. No need for the wrapping function.

I'd like to avoid using for .. of. Babel turns it into a whole lot of pretty expensive JavaScript. Can you use a standard for .. in or _.each() instead?

Missing trailing period.

One-line summary.

This should be using the standard function doc format.

"Python", "JavaScript"

Second sentence should be its own paragraph. One line summary.

One-line summary, standard function doc format (since we don't have properties in JavaScript and shouldn't pretend).

One-line summary.

Needs to return this.

What if we don't want auto-complete for the text field? Can this be optional?

Can you put the property on the next line? Reads a bit better.

This can use template literals.

Can you expand this to say more about what this does? How it formats it?

Looks like we only use draft this once. We can get rid of that variable.

For each of the built-in field descriptions, can you use the label (like "Branch", "Change Description", etc.) in the doc summary?

"Array"

Can you use data=[] in the function definition?

"Array"

Can this be data=[]?

"Array"

data=[]?

"Array"

data=[]?

afterEach needs to do RB.DnDUploader.instance = null. Not sure whether this change came before my cleanup, so maybe this is working around issues fixed there, but for reference, see commit 528b268.

The include should be indented 2 more spaces.

The include should be indented 1 more space.

Still needed?

Only a few comments. Looks good to me otherwise. I'll do a final pass after this.

Line's too long now. Review Bot's going to yell forever :/ Would be pretty cool to have dedent allow for some character at the end of a line that says "Join the next line and ignore any leading spaces of that line."
Maybe we can wrap right after <%-? Kinda ugly but... Less invasive.

As discovered recently, we'll need to wrap the file in (function() { ... })();

This might be faster as:

this._fieldName = this.fieldID.replace(/_(.)/g, (m, c) => c.toUpperCase());


Assuming you want to strip away all underscores and not just ones precedencing a letter.

Missing "Returns"
This should also go after useEditIconOnly.

Typo in "Markdown".

Ship It!