Add early return to diffProperties

[dmytrorykun]

Summary

This PR adds early return to the diff function. We don't need to go through all the entries of nextProps, process and deep-diff the values if nextProps is the same object as prevProps. Roughly 6% of all diffProperties calls can be skipped.

How did you test this change?

RNTester.

[react-sizebot]

Comparing: b5e5ce8...646fd87

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.min.js	=	168.91 kB	168.91 kB	=	52.94 kB	52.94 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	170.57 kB	170.57 kB	=	53.44 kB	53.44 kB
facebook-www/ReactDOM-prod.classic.js	=	590.83 kB	590.83 kB	=	103.91 kB	103.91 kB
facebook-www/ReactDOM-prod.modern.js	=	566.65 kB	566.65 kB	=	100.10 kB	100.10 kB
test_utils/ReactAllWarnings.js	Deleted	64.44 kB	0.00 kB	Deleted	16.10 kB	0.00 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
test_utils/ReactAllWarnings.js	Deleted	64.44 kB	0.00 kB	Deleted	16.10 kB	0.00 kB

Generated by 🚫 dangerJS against 646fd87

[javache]

Roughly 6% of all diffProperties calls can be skipped.

Can you check how much this is when passChildrenWhenCloningPersistedNodes is enabled?

[kassens]

Seems worthwhile even if it's lower after other optimizations. Do we need a feature flag?

Just make sure to not have the flag too long lived to avoid the extra check in the hot codepath.

[rickhanlonii]

I'm not sure this is safe, we already have an early return for each prop here, after some other logic that seems important:

react/packages/react-native-renderer/src/ReactNativeAttributePayload.js

Lines 336 to 338 in afea1d0

	if (prevProp === nextProp) {
	continue; // nothing changed
	}

Can we do a PR sync to test this before merging?

[dmytrorykun]

@javache I could'n test this change with passChildrenWhenCloningPersistedNodes = true. If I simply set it to true in ReactFabric-dev, the iOS app fails on multiple assertions.

[dmytrorykun]

@rickhanlonii I've patched the implementation/ReactFabric* files, and done a good amount of testing locally. Should I do something in addition to that? What do you mean by a "PR sync"?

[rickhanlonii]

Actually since it's feature flagged we can land it and enable the flag for testing