Merge pull request #121 from wjwitek/feature/derive-except

Add :except to derive options

Author: bernardd

lib/ex_aws/dynamo/encodable.ex

@@ -37,10 +37,10 @@ defimpl ExAws.Dynamo.Encodable, for: Any do
 
   def deriving(module, _struct, options) do
     extractor =
-      if only = options[:only] do
-        quote(do: Map.take(struct, unquote(only)))
-      else
-        quote(do: :maps.remove(:__struct__, struct))
+      cond do
+        only = options[:only] -> quote(do: Map.take(struct, unquote(only)))
+        except = options[:except] -> quote(do: Map.drop(struct, [:__struct__] ++ unquote(except)))
+        true -> quote(do: :maps.remove(:__struct__, struct))
       end
 
     quote do

test/lib/dynamo/encoder_test.exs

@@ -86,4 +86,16 @@ defmodule ExAws.Dynamo.EncoderTest do
     assert Encoder.encode(nil) == %{"NULL" => true}
     assert Encoder.encode(%{"key" => nil}) == %{"M" => %{"key" => %{"NULL" => true}}}
   end
+
+  test "encoder skips struct fields that are marked as excepted" do
+    user_except =
+      %Test.ExceptUser{email: "[email protected]", name: "Bob", age: 23, secret: "secret information"}
+      |> Encoder.encode_root()
+
+    assert %{
+             "age" => %{"M" => %{"N" => %{"S" => "23"}}},
+             "email" => %{"M" => %{"S" => %{"S" => "[email protected]"}}},
+             "name" => %{"M" => %{"S" => %{"S" => "Bob"}}}
+           } == Encoder.encode_root(user_except)
+  end
 end

test/support/mock_models.ex

@@ -17,3 +17,9 @@ defmodule Test.Nested do
   @derive {ExAws.Dynamo.Encodable, only: [:items]}
   defstruct items: [], secret: nil
 end
+
+defmodule Test.ExceptUser do
+  @moduledoc false
+  @derive {ExAws.Dynamo.Encodable, except: [:secret]}
+  defstruct [:email, :name, :age, :secret]
+end