phoenix-typescript

phoenix-typescript — the type-checker is a phoenix_sense gate

Encodes Mat Pocock's / Total TypeScript philosophy: TypeScript wasn't built to make JS "strongly typed" — it was built to give JS a fast, powerful feedback loop. Phoenix treats that loop as a first-class objective check.

Overview

The TypeScript language server and tsc form exactly the kind of objective signal Phoenix runs on: you write code, the checker gives instant pass/fail, you adjust — all before runtime. So in Phoenix, tsc --noEmit is a phoenix_sense check, on equal footing with tests. A change isn't done because it "looks typed"; it's done when the type check is green.

The gate

{"check":{"kind":"command_exit","target":["npx","tsc","--noEmit"],"expect":0}}

Run it as the inner-loop check for any TS edit (alongside the test gate). Red tsc = not done.

The feedback loop

  edit .ts ──► tsc --noEmit (phoenix_sense) ──► ok? ──yes──► run tests ──► done
                     │                            no
                     ▼
              read the type error (DATA, not a nuisance)
                     │
                     ▼
              fix the TYPE, not @ts-ignore the symptom ──► re-sense

Craft rules (each keeps the gate meaningful)

1. Work strict. "strict": true (and noUncheckedIndexedAccess) in tsconfig.json. Strictness is what makes the green check mean something; a loose config is a gate that can't fail.
2. Kill any and unsafe casts. any disables the checker locally — it's a hole in the gate. Prefer unknown + narrowing. An as cast asserts a truth the compiler can't verify; treat every cast as a place a real bug can hide, and justify it.
3. Derive, don't duplicate. One source of truth for a shape; derive the rest with typeof, indexed access (T["field"]), Parameters, ReturnType, Pick/Omit, as const. Duplicated types drift out of sync silently — exactly the failure types exist to prevent.
4. Type the boundaries. Validate external/untrusted data (API responses, params) at the edge (a schema validator), so the typed core can trust its inputs. Inside, let inference do the work — don't annotate what TS already knows.
5. No @ts-ignore / @ts-expect-error to pass the gate. Silencing the checker to get green is the TS equivalent of editing the test to match broken code. Fix the type. If a suppression is truly necessary, it needs a comment explaining why and a phoenix_sense test of the runtime behavior.