I'm certain that the maintainers of Bun have excellent understanding of their codebase. What makes you think that they don't? They wrote the code in the first place. They know the architecture. They know what pieces do what functions.
They did not write the rust code. AI wrote that code. Your response is side stepping the primary issue people have with the rewrite: no human has read and understood all the code AI wrote.
I agree but would propose the weaker argument: no set of human contributors have, put together, read and understood all the code. Even in artisanal-coded projects of sufficient size, it's rare that any one human has read and understood all of it.
I had an actual look at the code, and because it's a translation it's not just straight up de novo slop. The bits I saw were fairly straightforward 1:1 translations, so the Bun developers should still be familiar with the overall structure and logic.
I still think it's mad, but not quite as mad as you might first think from the headlines.
That doesn't change anything. No one can say with confidence, backed by proof, that the 1M slop is semantically equivalent to the old code. The code is a black box without that guarantee.
Presumably, in any sane process, changes would be split into small, reviewable PRs with people reasoning about the code. That wouldn't eliminate the possibility of bugs, but when done correctly it would give us substantially higher confidence that semantic equivalence is preserved.
With zero reviews and no one even reading the code, there's zero confidence. For all we know, the new Bun could contain a change that causes JS file reads to return a novel for a very specific filename, and the tests people keep pointing to, intended to downplay the malpractice, would never catch it. Tests cannot cover every contrived scenario that normal human beings would never think of writing.
