addStepDependency - Deleted

Examples:

Cannot add [...] as a dependency of [...]; the latter is deleted!
Cannot add [...] as a dependency of [...]; the former is deleted!

You've received this error because you've attempted to add a dependency between two steps, but one (or more) of those steps have been deleted. Typically this occurs when you cache a step — either as a property somewhere or in a closure — and that step is deduplicated, tree shaken, or otherwise disposed of before you come to reference it.

It's common to see this issue when using each():

function plan($source) {
  const $ids = get($source, "relatedIds");
  const $db = context().get("db");
  return each($ids, ($id) => {
    return loadOne($id, $db, null, batchGetThingById);
  });
}

Here the callback to each() references $db from the higher closure, but if this step were to have deduplicated before the each callback is called, you'd be handling a deleted step.

The solution is to ensure that closures you use never capture steps from a higher level; typically the solution is to move the fetching of the data into the callback:

function plan($source) {
  const $ids = get($source, "relatedIds");
  return each($ids, ($id) => {
    const $db = context().get("db");
    return loadOne($id, $db, null, batchGetThingById);
  });
}

Now the closure doesn't reference any extant $steps from outside of the closure, it is passed or constructs the steps it needs.