Add :any attribute type

README.md

@@ -95,6 +95,7 @@ attribute :serial_number,  :string,  length: 16
 attribute :wifi_ssid,      :string,  optional: true
 attribute :low_power_mode, :boolean, optional: true
 attribute :dns_servers,    [:string]
+attribute :user_data,      :any
 
 attribute :metadata do
   attribute :location,        :string
@@ -130,6 +131,7 @@ attribute <name>, <type>, <options>
 ```
 
 Types:
+- `any`
 - `boolean`
 - `integer`
 - `float`
@@ -160,6 +162,37 @@ Options:
 - `format` - Regular expression for the valid format of a string.
   - error - `wrong_format`
 
+The `any` type:
+- Intended to be a passthrough attribute where the value is not validated or coerced but the value must be not `nil` at a minimum if `optional: false`. The `any` type is useful if you want to split out schemas where the top level schema is a generic envelope containing a nested data structure that could possibly be of a polymorphic nature. **Example**:
+
+```elixir
+struct MQTT.AWS.Shadow.Update.V1
+
+name "aws_shadow_update"
+
+attribute :state do
+  attribute :desired, :any
+end
+```
+
+```elixir
+struct MQTT.Light.State.V1
+
+name "light_state"
+
+attribute [:schedule] do
+  attribute :start, :datetime
+  attribute :stop,  :datetime
+end
+```
+
+```elixir
+with {:ok, shadow}      <- Speck.validate(MQTT.AWS.Shadow.Update.V1, payload),
+     {:ok, light_state} <- Speck.validate(MQTT.Light.State.V1, shadow.state.desired) do
+  # do something with light_state
+end
+```
+
 ### Examples
 
 Example schemas can be found in [/protocol](https://github.com/amclain/speck/tree/main/protocol).

lib/speck.ex

@@ -103,6 +103,7 @@ defmodule Speck do
     end
   end
 
+  defp do_strict_validate(:any, value, _opts), do: value
   defp do_strict_validate(:boolean, value, _opts) when is_boolean(value), do: value
   defp do_strict_validate(:integer, value, _opts) when is_integer(value), do: value
   defp do_strict_validate(:float, value, _opts) when is_float(value), do: value
@@ -162,6 +163,8 @@ defmodule Speck do
     end)
   end
 
+  defp do_validate(:any, value, _opts), do: value
+
   defp do_validate(:boolean, value, _opts) when is_boolean(value), do: value
 
   defp do_validate(:integer, value, _opts) when is_integer(value), do: value

protocol/test/any.ex

@@ -0,0 +1,7 @@
+struct TestSchema.Any
+
+name "any"
+
+attribute :param1, :any
+attribute :param2, :any, strict: true
+attribute :param3, :any, optional: true

test/speck_test.exs

@@ -179,6 +179,26 @@ defmodule Speck.Test do
       }}
   end
 
+  test "can coerce a map with attribute type of any" do
+    params = %{
+      "param1" => %{},
+      "param2" => "valid"
+    }
+
+    assert Speck.validate(TestSchema.Any, params) ==
+      {:ok, %TestSchema.Any{
+        param1: %{},
+        param2: "valid"
+      }}
+  end
+
+  test "returns errors if required params of type any are missing" do
+    params = %{}
+
+    assert Speck.validate(TestSchema.Any, params) ==
+      {:error, %{param1: :not_present, param2: :not_present}}
+  end
+
   test "returns errors if items in a list of maps can't be coerced" do
     params = %{
       "devices" => [