Doc update

examples/contract/errors-01.exs

@@ -0,0 +1,14 @@
+defmodule UserContract do
+  use Drops.Contract
+
+  schema do
+    %{
+      required(:name) => string(:filled?),
+      required(:email) => string(:filled?)
+    }
+  end
+end
+
+errors = UserContract.conform(%{name: "", email: 312}) |> UserContract.errors()
+
+Enum.map(errors, &to_string/1)

lib/drops/contract.ex

@@ -34,6 +34,41 @@ defmodule Drops.Contract do
   @callback conform(data :: map(), schema :: Types.Map, keyword()) ::
               {:ok, map()} | {:error, list()}
 
+  @moduledoc """
+  Return errors from results returned by `conform/2`.
+
+  ## Examples
+
+      iex> defmodule UserContract do
+      ...>   use Drops.Contract
+      ...>
+      ...>   schema do
+      ...>     %{
+      ...>       required(:name) => string(:filled?),
+      ...>       required(:email) => string(:filled?)
+      ...>     }
+      ...>   end
+      ...> end
+      iex> errors = UserContract.conform(%{name: "", email: 312}) |> UserContract.errors()
+      [
+        %Drops.Contract.Messages.Error{
+          path: [:email],
+          text: "must be a string",
+          opts: %{args: [:string, 312], predicate: :type?}
+        },
+        %Drops.Contract.Messages.Error{
+          path: [:name],
+          text: "must be filled",
+          opts: %{args: [""], predicate: :filled?}
+        }
+      ]
+      iex> Enum.map(errors, &to_string/1)
+      ["email must be a string", "name must be filled"]
+
+  """
+  @callback errors({:ok, map()}) :: []
+  @callback errors({:error, map()}) :: [Drops.Contract.Messages.Error.t()]
+
   defmacro __using__(opts) do
     quote do
       use Drops.Validator

lib/drops/contract/messages.ex

@@ -2,6 +2,8 @@ defmodule Drops.Contract.Messages do
   defmodule Error do
     alias __MODULE__
 
+    @type t :: %__MODULE__{}
+
     defstruct [:path, :text, :opts]
 
     defimpl String.Chars, for: Error do