Merge branch 'derekkraan-master'

lib/norm.ex

@@ -16,6 +16,7 @@ defmodule Norm do
     Schema,
     Selection,
     Spec,
+    Delegate
   }
 
   @doc false
@@ -150,6 +151,20 @@ defmodule Norm do
     Spec.build(predicate)
   end
 
+  @doc ~S"""
+  Allows encapsulation of a spec in another function. This enables late-binding of
+  specs which enables definition of recursive specs.
+
+  ## Examples:
+      iex> conform!(%{"value" => 1, "left" => %{"value" => 2, "right" => %{"value" => 4}}}, Norm.Core.DelegateTest.TreeTest.spec())
+      %{"value" => 1, "left" => %{"value" => 2, "right" => %{"value" => 4}}}
+      iex> conform(%{"value" => 1, "left" => %{"value" => 2, "right" => %{"value" => 4, "right" => %{"value" => "12"}}}}, Norm.Core.DelegateTest.TreeTest.spec())
+      {:error, [%{input: "12", path: ["left", "right", "right", "value"], spec: "is_integer()"}]}
+  """
+  def delegate(predicate) do
+    Delegate.build(predicate)
+  end
+
   @doc ~S"""
   Creates a re-usable schema. Schema's are open which means that all keys are
   optional and any non-specified keys are passed through without being conformed.

lib/norm/core/delegate.ex

@@ -0,0 +1,15 @@
+defmodule Norm.Core.Delegate do
+  @moduledoc false
+
+  defstruct [:fun]
+
+  def build(fun) when is_function(fun, 0) do
+    %__MODULE__{fun: fun}
+  end
+
+  defimpl Norm.Conformer.Conformable do
+    def conform(%{fun: fun}, input, path) do
+      Norm.Conformer.Conformable.conform(fun.(), input, path)
+    end
+  end
+end

test/norm/core/delegate_test.exs

@@ -0,0 +1,35 @@
+defmodule Norm.Core.DelegateTest do
+  use Norm.Case, async: true
+
+  defmodule TreeTest do
+    def spec() do
+      schema(%{
+        "value" => spec(is_integer()),
+        "left" => delegate(&TreeTest.spec/0),
+        "right" => delegate(&TreeTest.spec/0)
+      })
+    end
+  end
+
+  describe "delegate/1" do
+    test "can write recursive specs with 'delegate'" do
+      assert {:ok, _} = conform(%{}, TreeTest.spec())
+
+      assert {:ok, _} =
+               conform(
+                 %{"value" => 4, "left" => %{"value" => 2}, "right" => %{"value" => 12}},
+                 TreeTest.spec()
+               )
+
+      assert {:error, [%{input: "12", path: ["left", "left", "value"], spec: "is_integer()"}]} =
+               conform(
+                 %{
+                   "value" => 4,
+                   "left" => %{"value" => 2, "left" => %{"value" => "12"}},
+                   "right" => %{"value" => 12}
+                 },
+                 TreeTest.spec()
+               )
+    end
+  end
+end