Typed Durable Object Storage

TypedDurableObjectStorage.ts

import type { Jsonify } from "type-fest";

// Define new storage types here and below and the storage below will automatically use them.
// prettier-ignore
type TypedDurableObjectStorageValue<Key extends string> = Jsonify<
  | Key extends "simple" ? boolean : never 
  | Key extends "complex" ? { age: number } | { name: string } : never
  | Key extends `template:type:known` ? number : never
  | Key extends `template:type:${string}` ? string | number : never
>;

type TypedDurableObjectStorageKey<Key extends string = string> = TypedDurableObjectStorageValue<Key> extends never
  ? Key
  : never;

interface TypedDurableObjectStorageCommon {
  get: <Key extends TypedDurableObjectStorageKey>(
    key: Key,
    options?: DurableObjectGetOptions
  ) => Promise<TypedDurableObjectStorageValue<Key> | undefined>;
  list: <Prefix extends string = string>(
    options?: Omit<DurableObjectListOptions, "prefix"> & { prefix?: Prefix }
  ) => Promise<Map<string, TypedDurableObjectStorageValue<`${Prefix}${string}`>>>;
  put: (<Key extends TypedDurableObjectStorageKey>(
    key: Key,
    value: TypedDurableObjectStorageValue<Key>,
    options?: DurableObjectPutOptions
  ) => Promise<void>) &
    (<Key extends TypedDurableObjectStorageKey>(
      entries: { [key in Key]: TypedDurableObjectStorageValue<Key> },
      options?: DurableObjectPutOptions
    ) => Promise<void>);
  delete: (<Key extends keyof TypedDurableObjectStorageKey>(
    key: Key,
    options?: DurableObjectPutOptions
  ) => Promise<boolean>) &
    ((keys: TypedDurableObjectStorageKey[], options?: DurableObjectPutOptions) => Promise<number>);
  getAlarm: DurableObjectStorage["getAlarm"];
  setAlarm: DurableObjectStorage["setAlarm"];
  deleteAlarm: DurableObjectStorage["deleteAlarm"];
}

interface TypedDurableObjectTransaction extends TypedDurableObjectStorageCommon {
  rollback: DurableObjectTransaction["rollback"];
}

interface TypedDurableObjectStorage extends TypedDurableObjectStorageCommon {
  transaction: <T>(closure: (txn: TypedDurableObjectTransaction) => Promise<T>) => Promise<T>;
  deleteAll: DurableObjectStorage["deleteAll"];
}

export default TypedDurableObjectStorage;

get(keys:) is unimplemented—I’ll update this if someone figures it out. I didn’t use it in my codebase so wasn’t too bothered.