feat: errdefer

[gjuchault]

function* errdefer<Error>(
  callback: (error: Error) => void | Promise<void>
): Generator<Errdefer<Error>, void, unknown>;

This method is similar to errdefer in other languages (eg. zig). It allows to cleanup eventual leftovers when a method partially failed. Similar to a finally keyword.
It takes the error as parameter if you need it

Example:

let globalTimeout1: NodeJS.Timeout;
let globalTimeout2: NodeJS.Timeout;

// Two dependency starting a long-living process like a timeout or a database connection
const genLongLivingDependency1 = gen(async function longLivingDependency() {
  globalTimeout1 = setTimeout(() => {}, 1000);
  return "done";
});

const genLongLivingDependency2 = gen(async function longLivingDependency() {
  globalTimeout2 = setTimeout(() => {}, 1000);
  return "done";
});

const genFailingDependency = gen(async function failingDependency() {
  throw new Error("some failing dependency");
});

async function* main() {
  const dependency1 = yield* genLongLivingDependency1();
  // this will be called if `main` has a failure somewhere
  yield* errdefer(() => clearTimeout(globalTimeout1));

  const dependency2 = yield* genLongLivingDependency2();
  // this will be called if `main` has a failure somewhere, after the first errdefer
  yield* errdefer(() => clearTimeout(globalTimeout2));

  // since this is failing, it will call every errdefer callback, evaluated in reverse order
  const failingDependency = yield* genFailingDependency();

  return [dependency1, dependency2, failingDependency];
}