Version 8 is not compatible with Safari 16.3 and below

[gzurbach]

Howdy!

We've recently upgraded JSDiff from version 7.0.0 to 8.0.1 in our project.

Shortly after, we began receiving reports from customers that our web app was broken. After some investigation, we found that the issue affects users on legacy browsers, specifically Safari 14, 15, and 16.

The root cause appears to be this regular expression: https://github.com/kpdecker/jsdiff/blob/27e6c81b2fbbe057cb6d296be0995c4140a2a815/src/diff/sentence.ts#L6C1-L6C45

Testing the regex shows a warning:

Which is confirmed by caniuse which shows that lookbehind assertions are not supported in those versions of Safari.

We recommend either updating the release notes to clearly indicate that legacy browser support has been dropped, or modifying the regex to maintain compatibility.

Thanks again for maintaining such a great library!

[ExplodingCabbage]

Oh man, shame on me - I knew about this specific issue, had hit it before, and carefully avoided introducing the same bug when making other changes in v8 that were similar to the one in diffSentences (see

jsdiff/src/util/string.ts

Lines 106 to 116 in 27e6c81

	// Yes, this looks overcomplicated and dumb - why not replace the whole function with
	// return string match(/\s*$/)[0]
	// you ask? Because:
	// 1. the trap described at https://markamery.com/blog/quadratic-time-regexes/ would mean doing
	// this would cause this function to take O(n²) time in the worst case (specifically when
	// there is a massive run of NON-TRAILING whitespace in `string`), and
	// 2. the fix proposed in the same blog post, of using a negative lookbehind, is incompatible
	// with old Safari versions that we'd like to not break if possible (see
	// https://github.com/kpdecker/jsdiff/pull/550)
	// It feels absurd to do this with an explicit loop instead of a regex, but I really can't see a
	// better way that doesn't result in broken behaviour.

); I feel dumb for screwing up this one.

Will fix tomorrow.

[gzurbach]

No problem at all, thanks for the quick turnaround 👍