[jrpelkonen]

The typestate pattern common in Rust applications allows the compiler to verify that the operations are executed in the right order and that previous states are not accidentally referenced. Here’s a good description: https://cliffle.com/blog/rust-typestate/

[jackfranklyn]

Thanks for the link - typestate is exactly the kind of compile-time guarantee I wish we had in JS/TS land. The pattern would be perfect for enforcing "you can't call postToAccounting() until validateTotals() has been called" at the type level.

We're in Node.js so the best we can do is runtime checks and careful typing. I've experimented with builder patterns that sort of approximate this - each method returns a new type that only exposes the valid next operations - but it's clunky compared to proper typestate.

The real benefit isn't just preventing out-of-order calls, it's making invalid states unrepresentable. Half our bugs come from "somehow this transaction reached step 9 without having the field that step 5 should have populated."