Function modify

packages/effect/src/unstable/persistence/KeyValueStore.ts:785–798

(key: string, f: (value: S["Type"]) => S["Type"])

  const set = (key: string, value: S["Type"]) => Effect.flatMap(encode(value), (json) => self.set(key, json))

  const modify = (key: string, f: (value: S["Type"]) => S["Type"]) =>
    Effect.flatMap(
      get(key),
      (o) => {
        if (Option.isNone(o)) {
          return Effect.succeedNone
        }
        const newValue = f(o.value)
        return Effect.as(
          set(key, newValue),
          Option.some(newValue)
        )
      }
    )

  return {
    [SchemaStoreTypeId]: SchemaStoreTypeId,