`parseDiffFromFile` defaults to low-specificity cache key

[jonatanklosko]

The docs currently say:

If both oldFile and newFile have a cacheKey, the resulting FileDiffMetadata will automatically receive a combined cache key (format: oldKey:newKey).

It would be fair to assume that if cacheKey is not set, it will not be cached. However, the current implementation defaults each file cache key to file name:

pierre/packages/diffs/src/utils/parseDiffFromFile.ts

Lines 38 to 46 in 39ef68a

	const fileData = processFile(patch, {
	cacheKey: (() => {
	const oldCacheKey = oldFile?.cacheKey ?? oldFile?.name;
	const newCacheKey = newFile?.cacheKey ?? newFile?.name;
	if (oldCacheKey != null && newCacheKey != null) {
	return oldCacheKey + ':' + newCacheKey;
	}
	return oldCacheKey ?? newCacheKey;
	})(),

Consequently, when using parseDiffFromFile for two subsequent changes of the same file, the renderer uses wrong cached information and throws:

DiffHunksRenderer.processDiffResult: deletionLine and additionLine are null, something is wrong

Given the above, I think either the docs should be clarified, or there should be no cacheKey generated unless explicitly specified (safer default).

An immediate fix on the user side is to specify a more specific cacheKey on each file, such as "{file_name}:{hash(file_content)}".

[amadeus]

Oh yeah, that was a change that slipped through with the edit feature that I ultimately never saw, i'll need to dig into this to figure out why it was changed and if it's necessary. Thanks for the callout!

[AbarnaaSree]

I'd like to work on this. I'll investigate whether removing the filename fallback affects the edit feature and propose a fix if it doesn't.