# `AshPhoenix.Inertia.Error`
[🔗](https://github.com/ash-project/ash_phoenix/blob/v2.3.21/lib/ash_phoenix/inertia/error.ex#L6)

Provides a mapping from an Ash Error type to a plain map that can be used with the `Inertia.Controller.assign_errors/2` function.

Note this module is only available when the `:inertia` dependency is included in your application.

## Typical usage with Inertia

Inertia users will typically pass Ash errors directly into the `Inertia.Controller.assign_errors/2` function in their controllers.
Internally the Inertia library will use the `Inertia.Errors` protocol to transform the Ash Error to a plain map for JSON serialization.

```elixir
  def create(conn, params) do
    case MyApp.Posts.create(params, actor: conn.assigns.current_user) do
      {:ok, post} ->
        redirect(conn, to: ~p"/posts/#{post.slug}")

      {:error, errors} ->
        conn
        |> assign_errors(errors)
        |> render_inertia("CreatePost")
    end
  end
```

The `Inertia.Errors` protocol is implemented for common error types and the Ash error classes, such as `Ash.Error.Invalid` and `Ash.Error.Forbidden`.
If you have a situation where there is no protocol implementation for your error type, you may need to call `Ash.Error.to_error_class/1` on the error
first, before passing it to ` Inertia.Controller.assign_errors/2`, or providing an implementation of the `Inertia.Errors` protocol for the error type.

# `to_errors`

```elixir
@spec to_errors(error_or_errors :: term(), message_func :: function()) :: %{
  required(String.t()) => String.t()
}
```

Converts an error, or list of errors to a map of error field to error message.

Nested field errors are flattened with the error path added as a dotted prefex, eg

```elixir
%{
  "user.contact.email_address" => "Is required"
}
```

## Parameters

 - `error_or_errors` (required) The error struct or list
 - `message_func` (optional) A function to transform a tuple of message string and variables map to a single string.

## Examples

    iex> AshPhoenix.Inertia.Error.to_errors(
    iex>   %Ash.Error.Action.InvalidArgument{
    iex>    path: [:customer, :contact],
    iex>    field: :email,
    iex>    message: "%{email} is already taken",
    iex>    vars: %{email: "acme@example.com"}
    iex>  }
    iex>)
    %{"customer.contact.email" => "acme@example.com is already taken"}

    iex> AshPhoenix.Inertia.Error.to_errors(
    iex>   %Ash.Error.Invalid{
    iex>    errors: [
    iex>      %Ash.Error.Action.InvalidArgument{
    iex>        path: [:customer, :contact],
    iex>        field: :email,
    iex>        message: "%{email} is already taken",
    iex>        vars: %{email: "acme@example.com"}
    iex>      },
    iex>      %Ash.Error.Action.InvalidArgument{
    iex>        path: [:product],
    iex>        field: :sku,
    iex>        message: "%{product_name} is out of stock",
    iex>        vars: %{product_name: "acme powder"}
    iex>      }
    iex>    ]
    iex>  }
    iex>)
    %{
      "customer.contact.email" => "acme@example.com is already taken",
      "product.sku" => "acme powder is out of stock"
    }

---

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