RequestValidator

A blazing fast request validator for your phoenix app, which validates a request body before hitting the request handler in the controller.

Why RequestValidator

It's common for a web service to validate incoming data. The most common layer where this is done is at the controller level and this sometimes leads to having a bloated controller. But with RequestValidator, you move the validation logic to a layer just before the controller and your controller is now free from doing validation.

Installation

The package can be installed by adding request_validator to your list of dependencies in mix.exs:

def deps do
  [
    {:request_validator, "~> 0.6"}
  ]
end

Usage

First of all, you need to define a validation schema to be used against the incoming data.

defmodule App.Requests.Registration do
  use Request.Validator
  
  # Get the validation rules that apply to the incoming request.
  @impl Request.Validator
  def rules(_) do
    [
      email: ~w[required email]a,
      first_name: ~w[required string]a,
      last_name: ~w[required string]a,
      password: [:required, :string, {:min, 8}, :confirmed]
    ]
  end

  # Determine if the user is authorized to make this request.
  @impl Request.Validator
  def authorize(_), do: true
end

The above validation schema can now be used;

defmodule App.UserController do
  use AppWeb, :controller

  plug Request.Validation.Plug,
    register: App.Requests.Registration

  def register(conn, params) do
    case App.UserService.create(params) do
      :ok ->
        conn
        |> put_status(201)
        |> json(%{message: "Account created successfully"})
      {:error, msg} ->
        conn
        |> put_status(500)
        |> json(%{message: msg})
    end
  end
end

As you can see in the controller, the register handler does not need to worry about validating the incoming request because RequestValidator will handle that automatically and send the right response if the request fails validation based on the given validation schema.

You can specify validation schema for each of the handlers in a controller:

defmodule App.UserController do
  use AppWeb, :controller

  plug Request.Validation.Plug,
    login: App.Requests.Login,
    register: App.Requests.Registration

  ...
end

Full documentation can be found at https://hexdocs.pm/request_validator.

Ecto Support

In some cases, your application already makes use of the ecto library. I'm glad to tell you that this library has support when the rule method returns an Ecto.Changeset struct so that you can make use of the advantages provided by this library without rewriting your validation logic. See the example below:

defmodule App.SomeEctoSchema do
  use Ecto.Schema
  import Ecto.Changeset

  embedded_schema do
    field(:name, :string)
    field(:email, :string)
    field(:age, :integer)
    field(:password, :string)
  end

  @doc false
  def changeset(attrs), do: changeset(%__MODULE__{}, attrs)

  @doc false
  def changeset(struct, attrs) do
    struct
    |> cast(attrs, [:name, :email, :age, :password])
    |> validate_required([:name, :email, :age, :password])
    |> validate_number(:age, less_than_or_equal_to: 32)
  end
end

defmodule App.Requests.TestRequest do
  use Request.Validator

  alias App.SomeEctoSchema

  @impl Request.Validator
  def rules(conn), do: SomeEctoSchema.changeset(conn.params)

  @impl Request.Validator
  def authorize(_), do: true
end

Custom Validation Rules

This library provides a variety of helpful rules, however, you might want to define some rules to house your validation logic. To achieve this, you need to create your own rules module, extend the default rules and update the library configuration;

defmodule App.Validation.Rules do
  use Request.Validator.Rules # grab default rules provided by the library

  @spec uppercase(binary(), keyword()) :: :ok | {:error, binary()}
  def uppercase(value, fields: _fields, field: _field) do
    case String.upcase(value) do
      ^value ->
        :ok
      _ ->
        {:error, "This field must be uppercase."}
    end
  end
end

After defining a module with your custom rules, you will need to update your application configuration:

config :request_validator, rules_module: App.Validation.Rules

Once the new rule has been added and configuration updated, it can now be used:

# ...
  def rules(_) do
    [
      name: ~w[required string uppercase]a
    ]
  end
# ...

Note that if your rule accepts options/parameters, its function definition should have an arity of 3, and the second argument will be the option provided when the rule is used, ex: {:custom_rule, options}

TODOS

License

RequestValidator is released under the MIT License - see the LICENSE file.