This was intentional to avoid mutating the object.

Am I remembering correctly? @cknitt

Oh, I missed that switching arguments position between key and props. It makes sense.

It doesn't mutate the props object. It'll create the new object with key field and then mutate it.

Before:

1. Create empty obj
2. Create obj with key
3. Mixing props and obj with key to the empty object

After:

1. Create obj with key
2. Mixing props to the obj with key

I don't understand what you want to say 😅

Sorry for the lack of explanation.
I meant I think that the existing implementation is more appropriate.

What do you think? @cknitt

This should work like the previous implementation (no mutation), but with one less object allocation. Looks good to me.

(Provided that the caller passes a different {"key": key} object every time, but that seems to be the case and this is an internal function anyway.)

Okay. It seems unlikely that Object.assign({"key": key}, props) would change the value of key at runtime, since props would not be able to contain key when the JSX ppx transforms the component application.

LGTM.