Raise on non-existing fields in Protobuf.Builder.new/2

lib/protobuf.ex

@@ -16,6 +16,10 @@ defmodule Protobuf do
       def new(attrs) do
         Protobuf.Builder.new(__MODULE__, attrs)
       end
+
+      def new!(attrs) do
+        Protobuf.Builder.new!(__MODULE__, attrs)
+      end
     end
   end
 

lib/protobuf/builder.ex

@@ -4,13 +4,46 @@ defmodule Protobuf.Builder do
   end
 
   def new(mod, attrs) do
+    new_maybe_strict(mod, attrs, _strict? = false)
+  end
+
+  def new!(mod, attrs) do
+    new_maybe_strict(mod, attrs, _strict? = true)
+  end
+
+  def field_default(_, %{default: default}) when not is_nil(default), do: default
+  def field_default(_, %{repeated?: true}), do: []
+  def field_default(_, %{map?: true}), do: %{}
+  def field_default(:proto3, props), do: type_default(props.type)
+  def field_default(_, _), do: nil
+
+  def type_default(:int32), do: 0
+  def type_default(:int64), do: 0
+  def type_default(:uint32), do: 0
+  def type_default(:uint64), do: 0
+  def type_default(:sint32), do: 0
+  def type_default(:sint64), do: 0
+  def type_default(:bool), do: false
+  def type_default({:enum, _}), do: 0
+  def type_default(:fixed32), do: 0
+  def type_default(:sfixed32), do: 0
+  def type_default(:fixed64), do: 0
+  def type_default(:sfixed64), do: 0
+  def type_default(:float), do: 0.0
+  def type_default(:double), do: 0.0
+  def type_default(:bytes), do: <<>>
+  def type_default(:string), do: ""
+  def type_default(_), do: nil
+
+  defp new_maybe_strict(mod, attrs, strict?) do
     case attrs do
       %{__struct__: _} ->
         attrs
 
       _ ->
-        msg = struct(mod.__default_struct__(), attrs)
         props = mod.__message_props__()
+        default_struct = mod.__default_struct__()
+        msg = if strict?, do: struct!(default_struct, attrs), else: struct(default_struct, attrs)
 
         Enum.reduce(props.embedded_fields, msg, fn k, acc ->
           case msg do
@@ -36,28 +69,4 @@ defmodule Protobuf.Builder do
         end)
     end
   end
-
-  def field_default(_, %{default: default}) when not is_nil(default), do: default
-  def field_default(_, %{repeated?: true}), do: []
-  def field_default(_, %{map?: true}), do: %{}
-  def field_default(:proto3, props), do: type_default(props.type)
-  def field_default(_, _), do: nil
-
-  def type_default(:int32), do: 0
-  def type_default(:int64), do: 0
-  def type_default(:uint32), do: 0
-  def type_default(:uint64), do: 0
-  def type_default(:sint32), do: 0
-  def type_default(:sint64), do: 0
-  def type_default(:bool), do: false
-  def type_default({:enum, _}), do: 0
-  def type_default(:fixed32), do: 0
-  def type_default(:sfixed32), do: 0
-  def type_default(:fixed64), do: 0
-  def type_default(:sfixed64), do: 0
-  def type_default(:float), do: 0.0
-  def type_default(:double), do: 0.0
-  def type_default(:bytes), do: <<>>
-  def type_default(:string), do: ""
-  def type_default(_), do: nil
 end

test/protobuf/builder_test.exs

@@ -49,4 +49,10 @@ defmodule Protobuf.BuilderTest do
     msg = %Foo{}
     assert msg == Foo.new(msg)
   end
+
+  test "new!/2 raises for fields that don't exist in the schema" do
+    assert_raise KeyError, fn ->
+      Foo.new!(nonexisting_field: "foo")
+    end
+  end
 end