Thread

1. dimbletimbers · 1790559269 · focus · HN ↗

   A defense of human code review I wish I saw more often, especially in light of the concerns people have about cognitive/comprehension debt: comprehension redundancy. At the end, if taken seriously, at least two people understand how the feature works (even if that number is, on average, trending closer to between one and zero). Ideally at least one of the two also comes away with a better understanding of the wider system and how the feature fits into or stands out from that landscape.

   1. atomicnumber3 · 1790560581 · focus · HN ↗

      If only one person knows the code, then PR time isn't going to save you.

      I'm tech lead and I basically don't review PRs, and I tell people this, with a caveat - if you can tell me what you specifically want me to review, for what specific purpose, I'm happy to!

      So "can you review this bit for race conditions" is great, love it. This forces people to actually think about what in their code they should be suspicious of, if anything.

      "Can you review this" [link to PR] is getting a rubber stamp because humans have never been good enough at "just spotting bugs" to make this worth it and now any LLM is better than a human.

      And for the purpose of understanding - PR time is too late. I have not reviewed a PR ("for real") in a long time and yet I could tell you how every system my people have built works down to a very fine level of detail. And it's because _we talk to each other!_ We don't just chill in the same slack channel and code independently, we all value each others brains and want each others inputs because we know it will improve our product and we value what perspectives others will bring.

      Trying to learn via PR is a sad substitute for real collaboration and teamwork.

      1. 20k · 1790569941 · focus · HN ↗

         This is wild to read, I always review PRs and frequently find bugs or significant problems in them that get them bounced back

         1. onion2k · 1790578811 · focus · HN ↗

            That's a strong signal that your team isn't doing well. Significant problems should have been spotted at a software design stage, or raised in standups, or identified in a pairing session. The earlier you can find an issue the simpler it is to fix, so waiting until the last moment (e.g. PR) means you're spending far more time fixing issues than necessary.

            As for finding bugs, what happens if you miss them? Do they go out to production and potentially lose user data? Finding bugs in PR is a big problem. For a start it shows your automated tests aren't good enough, and secondly it shows the devs aren't checking their code works well enough.

            If you do them at all, PRs should be a gate for checking whether the code meets the team's quality bar, not if it even works. The team should be able to deliver working code without them.

            1. 20k · 1790617800 · focus · HN ↗

               Its a strong signal that developers make mistakes, code review has empirically been shown to be one of the best ways of uncovering defects. If you aren't finding bugs that people have written during code review (or you're not doing code review at all like the person I was replying to!), they're slipping rightwards

               Bugs usually include business logic edge cases, and significant problems include someone realising while reading the PR that we can actually create a much better solution to the underlying problem. Ideally that realisation would happen prior to the PR being offered, but that's also not really how humans work

               Example: During a PR review for a graphical feature for a game, someone reading it realises that we can actually have a significantly better solution to the underlying problem. You can't catch this in testing, because it doesn't even make sense conceptually to test it. It also sucks that it happened after someone put in a lot of work, but with graphics development you expect a lot of what you write to get canned and replaced with a better solution, because the technology evolves over time. The work is iterative towards the final goal anyway

               Its also very common to miss subtle edge cases with graphics hardware, eg someone misunderstood the intricacies of GPU hardware, or a team member has relevant experience that someone else does not have. Or they missed a problematic memory access pattern on some hardware for example. Or something simple like they've technically forgotten a barrier, that the validation layer doesn't report for some reason

               Eg: The function "tanh" is broken on some AMD GPU hardware, and should never be used under any circumstances. The actual GPU implementation of it is just screwed. Ideally everyone would know this, but its a very common function to crop up during specific graphics algorithms (as it smoothly remaps the range [-inf, +inf] -> [-1, 1]). So occasionally I've spotted that, and had to explain that we need to use an approximation instead, and then now everyone knows . It rarely gets caught during testing setups, because people don't know they need to include that hardware in their tests in the first place

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