Improve diffing of line endings

[jamesmoss]

I ran into the same issue this person did today #3847 where the diffs looked identical in a failing test. I managed to track it down to a library I was using that was outputting line endings with \r\n. As I'm on a Mac, the strings in my test fixtures that get passed into .toBe() ended with just \n.

This behavior was pretty confusing. Is there a way to improve the diffing to make it clearer what the issue was?

[hi-ogawa]

It looks like Jest had similar requests, but maybe lf LF vs CRLF issues are still same

• Better reporting for string differences jestjs/jest#6881
• Snapshot comparison failing but results look identical jestjs/jest#9865

Any idea would be welcome, but not sure what's the best approach.

[hi-ogawa]

Probably string diff has changed since #3847. This is how it looks now, which shows a diff line by line:
https://stackblitz.com/edit/vitest-dev-vitest-nxszdaq6?file=test%2Frepro.test.ts

[jamesmoss]

So that works well for shorter strings, but with my longer example below the problematic carriage return characters get truncated from the end of the AssertionError message.

[jamesmoss]

Not sure how you'd solve this in a sane way, perhaps a lookup table of all the whitespace characters and show those differently in diffs? That feels pretty unmanagable.

What about showing the unicode representation for the first non-matching character in the diff? In my case this probably would be enough to make me realise what was going on here. In fact better truncation of the AssertionError message might be the easiest solution. instead of truncating from the start of the string, use N number of characters either side of the first non-matching character.