Fix multiline TextInput crash when inserting/removing lots of text

[tido64]

Summary

Multiline TextInput can crash when really long texts are inserted and removed quickly. This is caused by the fact that -[NSAttributedString string] doesn't really return a copy, and may mutate the string while it is being used by convertIdToFollyDynamic. See microsoft#489 (comment) for more details on the issue.

This issue was originally reported in microsoft#486 and was fixed in microsoft#489.

Changelog

[iOS] [Fixed] - Fix multiline TextInput crash when inserting/removing lots of text

Test Plan

1. Open RNTester > TextInput
2. Search for a multiline example
3. Copy some large text and paste it into the text input view
4. Remove some (or all) text
5. Repeat steps 3-4

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: e206e34

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	6,764,990	0
android	hermes	armeabi-v7a	6,427,925	0
android	hermes	x86	7,152,623	0
android	hermes	x86_64	7,042,550	0
android	jsc	arm64-v8a	8,936,316	0
android	jsc	armeabi-v7a	8,591,663	0
android	jsc	x86	8,767,077	0
android	jsc	x86_64	9,342,614	0

Base commit: e206e34

[facebook-github-bot]

@hramos has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[facebook-github-bot]

@JoshuaGross has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[shergin]

For the reference: https://developer.apple.com/documentation/foundation/nsattributedstring/1412616-string?language=objc

[react-native-bot]

This pull request was successfully merged by @tido64 in 15dda0a.

^{When will my fix make it into a release? | Upcoming Releases}