# `VerifiedPubSub.PayloadError`
[🔗](https://github.com/CuriousCurmudgeon/verified_pubsub/blob/v0.1.0/lib/verified_pubsub/payload_error.ex#L1)

The error for a broadcast payload that does not match the shape that the manifest
declares.

`broadcast/4` and `broadcast!/4` both raise it. A shape violation is a bug in the code of
the caller, not a failure that the caller can expect. So `{:error, _}` only reports a
transport failure, which a caller can handle.

The error reports every problem at once, not only the first:

    invalid payload for :pets :adopted in MyApp.Topics:

      * missing required key: :id
      * unexpected key: :extra — not declared on this event
      * :name is declared as :string, got: 42

# `problem`

```elixir
@type problem() ::
  {:not_a_map, term()}
  | {:struct_payload, module()}
  | {:missing, [atom()]}
  | {:unexpected, [atom()]}
  | {:type, atom(), VerifiedPubSub.Dsl.Field.type(), term()}
```

A problem with a payload. Each value is one of these:

  * `{:not_a_map, value}`: the payload is not a map.
  * `{:struct_payload, module}`: the payload is a struct of `module`, not a map.
  * `{:missing, names}`: the payload has no key for these required fields.
  * `{:unexpected, names}`: the payload has keys that the event does not declare.
  * `{:type, name, type, value}`: the value of the field `name` does not match `type`.

# `t`

```elixir
@type t() :: %VerifiedPubSub.PayloadError{
  __exception__: term(),
  event: atom(),
  manifest: module(),
  payload: term(),
  problems: [problem()],
  topic: atom()
}
```

The fields of the error:

  * `manifest`: the manifest that declares the event.
  * `topic`: the name of the topic.
  * `event`: the event of the broadcast.
  * `problems`: every problem with the payload.
  * `payload`: the payload of the broadcast.

---

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