Keep reference equality when possible in update()

[davidmason]

For $set and $apply it is cheap and easy to check whether the new value will
be identical (===) to the old value and create a new object only when this is not
the case. This will reduce excessive renders when using the pureRenderMixin.

The same should be possible for for merge, but is more complicated so is not
attempted here.

Addresses #1923

[davidmason]

I'm getting linting errors in a bunch of test files I haven't touched - is master failing these?

[davidmason]

Would this change be better against 0.13-stable?

[sophiebits]

If you rebase, the lint errors should be fixed.

[davidmason]

Thanks @spicyj, I think that fixed it.

[sebmarkbage]

FYI, this tool is deprecated in favor of immutable-js. I'm don't think we'll keep maintaining this repo. We can take this after we've cut our branch. However, if you want to keep using this tool I suggest you fork it and release your own npm package.

[davidmason]

if you want to keep using this tool I suggest you fork it and release your own npm package.

Might as well, can look at forking it next week.

[jimfb]

@sebmarkbage Are we ready to merge this, or do we just want to deprecate it and let @davidmason take the code from here?

[rdquintas]

Hi, was wondering if I could help here.
Is this still an open issue ?

[jimfb]

Ping @sebmarkbage. Are we ready to merge this, or do we just want to deprecate it and let @davidmason take the code from here?

[sophiebits]

@jimfb Feel free to merge this if it looks good to you.

[facebook-github-bot]

@davidmason updated the pull request.

[gaearon]

Thanks for contributing, @davidmason! I merged your PR locally but then tried to refactor it to avoid function allocations and the need to call getCurrentValue and getNextValue every time.

I submitted it in #6353 and kept all your commits attributed to you. I am keeping this PR open so when/if #6353 gets merged, this PR should appear merged as well (if I understand GitHub correctly 😅 ). Please check out #6353 and leave a note if I missed something. And thanks for getting this ball rolling!

[davidmason]

Cool, thanks for keeping this going :)

[facebook-github-bot]

@davidmason updated the pull request.

[gaearon]

I’m going to close this for the same reasons as #6353 (comment).
I think this direction will be best for everyone involved.

[facebook-github-bot]

@davidmason updated the pull request.