Formatting a 25M-line codebase overnight

(stripe.dev)

67 points | by r00k 2 hours ago

11 comments

  • nitwit005 1 minute ago
    > Given that complexity, the hypothesis was simple: tackle the hardest syntax first and the rest will follow.

    Always nice to see. I've seen people fall into the trap of designing for the common case, not realizing most of the code will be to deal with the less common cases.

  • CrzyLngPwd 53 minutes ago
    One of my first jobs was a small software company writing software for a small number of clients, in MS basic PDS.

    The lead developer didn't like to bother with formatting code, so I wrote a tool called makenice to format his nasty spaghetti gibberish into something with good indents and layout to make it easier for us normal people to parse.

    He was furious, literally spun in circles about it right in the office in front of everyone, so I wrote makenasty to format code into the way he appeared to like.

    I only shared makenasty/nice with a couple of the team, who loved it, as it allowed easy conversion between something readable and something the team lead like.

    He never knew about makenasty.

    • munk-a 18 minutes ago
      Outside of the naming - this is a perfectly sane thing to do for developer comfort and can usually be accomplished with simple transformations.

      There are often limitations (like manually added indentation/spacing for alignment) but as long as you're very intentional about what changes you'll allow and have a good understanding of the language it can be an extremely safe operation.

    • nitwit005 10 minutes ago
      If he didn't bother formatting code, it would seem impossible to create a tool that formatted code the way he preferred.
      • singpolyma3 5 minutes ago
        Sounds like he did format code, and even had opinions on how it should be formatted, but OP disagreed.
  • hobofan 38 minutes ago
    I'm surprised they went with a all-at-once reformat. Even when doing it over a weekend this is bound to mess with a lot of open PRs at their scale.

    I had to introduce a formatter in a few sizeable codebases in the past (few 100k to few million LOC), and I always did it incrementally via a script that reformatted all files that are not touched in any open PR. The initial run reformatted 95% of all files. Then I ran the script every day for ~two weeks and got up to 99.5% of all files and then manually each time one of the remaining ~dozen PRs that were WIP for longer were merged.

    • skydhash 30 minutes ago
      You can always let the team know so that they can apply the formatter on their PR branch.
  • munificent 29 minutes ago
    > We chose a Saturday to format the entire codebase to avoid merge conflicts. And while our test suite gave us high confidence we'd gotten everything right, it's always a bit daunting to have a diff so large that GitHub can't render it.

    The dart formatter has an internal sanity check. It walks through the unformatted and formatted strings in parallel skipping any whitespace. If any non-whitespace characters don't match, it immediately aborts. This ensures that the only thing the formatter changes is whitespace, and makes it much less spooky to run it blind on a huge codebase.

    That sanity check has saved my ass a couple of times when weird bugs crept in, usually around unusual combinations of language features around new syntax.

    (Unfortunately, the formatter in the past year has gotten a little more flexible about the kinds of changes it makes, including sometimes moving comments relatively to commas and brackets, so this sanity check skips some punctuation characters too, making it a little less reliable.)

  • varun_ch 1 hour ago
    I’m shocked at the 25M line part! That is a completely unfathomable amount of code for one codebase. I really want to know more about that.
    • bruckie 49 minutes ago
      Only 25 million? :) Google had billions a decade ago...

      https://research.google/pubs/why-google-stores-billions-of-l...

    • jsnell 1 hour ago
      Right, where is the rest of the code?
    • mr_mitm 1 hour ago
      They're up to 42 million now, as per the article
      • lukan 1 hour ago
        That sounds even more insane to me, but I guess most of that code does not really touch financial transactions, otherwise it would be a nightmare being responsible to verify that.
        • clintonb 15 minutes ago
          Ruby code touches financial transactions. Card payments were migrated to Java when I left in 2022. Non-card payments (e.g., ACH, checks, various wallets) were still processed by Ruby.

          PCI-related/vaulting code lived in its own locked-down repo. I think that was a mix of Go and Ruby.

          Once you have the foundations in place for account balances and the ledger, processing a payment isn’t that daunting. Those foundations, however, took a lot to build and evolve.

  • cadamsdotcom 18 minutes ago
    An insight about code is that compared to the scale we operate on data, code as text is tiny. Instantaneous git operations and “run this tool over all the code” are the norm even while we wait for LLMs to stream their tokens to stream back so tool calls can operate on it.

    That insight might seem obvious - but if you stay cognizant of it as you work, you can invent some pretty amazing tooling for yourself & your team.

  • burnte 59 minutes ago
    The floating spiral thing is so distracting I spent more time deleting it in Inspector than reading the article. I feel like they hate their readers. Awful.
  • hokkos 1 hour ago
    Now it makes me wonder, are those 45M LoC are untyped ?
  • exsol 1 hour ago
    [dead]
  • CrzyLngPwd 48 minutes ago
    Surely, it no longer needs to be human-readable, and the era of write-only code is finally upon us with the dawn of AI writing our mealtickets.

    Why bother formatting 25m lines of slop, and why is AI wasting tokens on making code look human-readable anyway?

  • andrewstuart 1 hour ago
    A major financial processing company writes it money handling systems in Ruby.

    Terrifying.

    • mbStavola 1 hour ago
      Considering that it's been doing so successfully at volume for just over 15 years, I think their language choice was fine.
    • sixo 1 hour ago
      This ought to change your mind about Ruby!
    • skinfaxi 1 hour ago
      Why is that terrifying?
      • fantasizr 36 minutes ago
        ive yet to see a compelling elitist programming language opinion. especially when used at big successful companies. these companies don't function in spite of their technology choices.
        • lstodd 24 minutes ago
          > these companies don't function in spite of their technology choices.

          shows you never worked at "big succesful companies".

      • Jtsummers 1 hour ago
        It's not particularly terrifying. Some people really just don't like Ruby.
      • mikedelago 49 minutes ago
        Some folks don't like shipping
    • sikozu 1 hour ago
      The systems have to be written in some kind of programming language, and I think Ruby is a perfectly fine choice.
      • Imustaskforhelp 1 hour ago
        Not denying that Ruby is a perfectly fine choice but within the article itself it says that Stripe runs the world's largest Ruby codebase so certainly it might be testing the constraints of the language.

        The thing I am interested is that I don't suppose that Stripe always had these many LOC's and so I would be curious to know if at any point as the codebase was increasing, were they looking at other new languages which were coming like golang or rust which was more suited for their work or not and what were there decisions/thinking process to continue using ruby.

        • clintonb 12 minutes ago
          LOC doesn’t have much to do with the “constraints of the language”.

          Stripe has dabbled in Golang. There is also a growing Java monorepo.

    • sunrunner 1 hour ago
      Things can always be worse. It could be PHP, for example.
      • burnte 45 minutes ago
        Facebook runs in it, so I think the language itself is probably a fine choice.
        • Twirrim 21 minutes ago
          It's almost like other factors than language choice are more important :)
    • semiquaver 1 hour ago
      I’d hardly call Sorbet Ruby :)
    • benbristow 1 hour ago
      [dead]