Allows skipping files during the transformation

lib/arc/actions/store.ex

@@ -56,6 +56,7 @@ defmodule Arc.Actions.Store do
   defp put_version(definition, version, {file, scope}) do
     case Arc.Processor.process(definition, version, {file, scope}) do
       {:error, error} -> {:error, error}
+      {:skip} -> {:skip}
       {:ok, file} ->
         file_name = Arc.Definition.Versioning.resolve_file_name(definition, version, {file, scope})
         file      = %Arc.File{file | file_name: file_name}

lib/arc/processor.ex

@@ -6,6 +6,7 @@ defmodule Arc.Processor do
 
   defp apply_transformation(file, :noaction), do: {:ok, file}
   defp apply_transformation(file, {:noaction}), do: {:ok, file} # Deprecated
+  defp apply_transformation(_file, :skip), do: {:skip}
   defp apply_transformation(file, {cmd, conversion, _}) do
     apply_transformation(file, {cmd, conversion})
   end

test/actions/store_test.exs

@@ -12,6 +12,15 @@ defmodule ArcTest.Actions.Store do
     def __versions, do: [:original, :thumb]
   end
 
+  defmodule SkipFileDummyDefinition do
+    use Arc.Actions.Store
+    use Arc.Definition.Storage
+
+    def validate(_), do: true
+    def transform(_, _), do: :skip
+    def __versions, do: [:original, :thumb]
+  end
+
   test "checks file existance" do
     assert DummyDefinition.store("non-existant-file.png") == {:error, :invalid_file_path}
   end
@@ -50,6 +59,12 @@ defmodule ArcTest.Actions.Store do
     end
   end
 
+   test "skip file does not try to store it" do
+      with_mock Arc.Storage.S3, [put: fn(SkipFileDummyDefinition, _, {%{file_name: "image.png", path: @img}, :scope}) -> {:error, {:http_error, 404, "XML"}} end] do
+        assert SkipFileDummyDefinition.store({%{filename: "image.png", path: @img}, :scope}) == {:ok, "image.png"}
+      end
+    end
+
   test "timeout" do
     Application.put_env :arc, :version_timeout, 1