Merge pull request #30 from ExpressApp/include-only-option

add :only option to include

Author: artemeff

lib/construct.ex

@@ -113,16 +113,36 @@ defmodule Construct do
   If included structure is invalid for some reason — this macro throws an
   `Struct.DefinitionError` exception with detailed reason.
   """
-  @spec include(t) :: Macro.t()
-  defmacro include(struct) do
+  @spec include(t, keyword) :: Macro.t()
+  defmacro include(struct, opts \\ []) do
     quote do
       module = unquote(struct)
 
+      opts = unquote(opts)
+      only = Keyword.get(opts, :only)
+
       unless Construct.__is_construct_module__(module) do
         raise Construct.DefinitionError, "provided #{inspect(module)} is not Construct module"
       end
 
-      Enum.each(module.__construct__(:types), fn({name, {type, opts}}) ->
+      types = module.__construct__(:types)
+
+      types =
+        if is_list(only) do
+          Enum.each(only, fn(field) ->
+            unless Map.has_key?(types, field) do
+              raise Construct.DefinitionError,
+                "field #{inspect(field)} in :only option " <>
+                  "doesn't exist in #{inspect(module)}"
+            end
+          end)
+
+          Map.take(types, only)
+        else
+          types
+        end
+
+      Enum.each(types, fn({name, {type, opts}}) ->
         Construct.__field__(__MODULE__, name, type, opts)
       end)
     end

test/integration/make_test.exs

@@ -441,6 +441,44 @@ defmodule Construct.Integration.MakeTest do
     assert {:ok, %{a: 0, b: "b", c: "from module"}} = make(module, %{b: "b"})
   end
 
+  test "structure with `include` and only option" do
+    include1_module = create_construct do
+      field :a
+      field :b
+    end
+
+    include2_module = create_construct do
+      field :c
+      field :d
+    end
+
+    include1 = name(include1_module)
+    include2 = name(include2_module)
+
+    module = create_construct do
+      include include1, only: [:a]
+      include include2, only: []
+      include include2, only: [:d]
+    end
+
+    assert {:ok, %{a: "a", d: "d"}} = make(module, %{a: "a", b: "b", c: "c", d: "d"})
+  end
+
+  test "structure with `include` where field in only option doesn't exist" do
+    include_module = create_construct do
+      field :a
+      field :b
+    end
+
+    include = name(include_module)
+
+    assert_raise(Construct.DefinitionError, "field :c in :only option doesn't exist in Construct.Integration.MakeTest_468", fn ->
+      create_construct do
+        include include, only: [:c]
+      end
+    end)
+  end
+
   test "field with `[CommaList, {:array, :integer}]` type" do
     module = create_construct do
       field :key, [CommaList, {:array, :integer}]