extendObservable: remove constraint for existing property

[davefeucht]

Currently extendObservable throws an error if you try to use it on a property which already exists in the target object/class. This makes it impossible to dynamically make an existing property observable.

• Added unit tests
• Updated changelog
• Updated /docs. For new functionality, at least API.md should be updated
• Added typescript typings
• Verified that there is no significant performance drop (npm run perf)

Feel free to ask help with any of these boxes!

The above process doesn't apply to doc updates etc.

[mweststrate]

Looking good! I think we are pretty close, left 2 comments

[mweststrate]

Approved! Thanks a lot.

This change might need backporting to MobX 4? cc @kr_anand_mishra

[davefeucht]

Yeah, I actually specifically need it for Mobx4 :)

[davefeucht]

Do you have an idea how long until it will be released, by the way?

[mweststrate]

I'm a little behind with cutting releases, but early next week should be doable I think. Would that work for you?

If interested, feel free to open a PR against mobx4-master as well and cherry-pick the changes (only test and implementation)

We are working on making that process smoother😅

[davefeucht]

Yeah, early next week should be fine. I’ll make an MR for mobx4-master first thing in the morning with just the code and tests.

[mweststrate]

THanks!