# `Macaw.Data.Derived.Output`
[🔗](https://github.com/dcoai/macaw_data/blob/v0.5.3/lib/macaw/data/derived/output.ex#L1)

A derived source's answer read as any source's (spec/02 §8.5): a `Macaw.Data.Source`
over an engine's last good output at one path, made by `Macaw.Data.Derived.Engine.source/3`.

- `describe/2` answers the output schema, `supports: []`, no parameters, and
  `viewer_independent` as the owner declared it;
- `fetch/2` answers the last good output whole, or `{:error, :loading}` before the first.
  It honors nothing, so the runtime finishes it (spec/01 §2.4);
- it does not push: its owner's engine is what changes it, and the owner tells readers
  (spec/01 §5).

So a derived source is another derived source's input and a slot's source alike, and the
conformance kit holds it as it holds any source.

# `t`

```elixir
@type t() :: %Macaw.Data.Derived.Output{
  delivery: Macaw.Data.Delivery.t() | nil,
  schema: Macaw.Data.Schema.t(),
  viewer_independent: boolean()
}
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*