Encode nil as null

changelog.md

@@ -35,3 +35,5 @@
      based on `record_type` and `map_type` options.
 * 2.8.1
    - Support 'object' as custom type properties
+* 2.8.2
+   - Encode atom `nil` as "null" for Elixir consumers

src/avro_primitive.erl

@@ -89,6 +89,9 @@ string_type()  -> type(?AVRO_STRING, []).
 -spec cast(avro_type(), term()) -> {ok, avro_value()} | {error, term()}.
 cast(Type, null) when ?IS_NULL_TYPE(Type) ->
   {ok, ?AVRO_VALUE(Type, null)};
+% For Elixir compatibility
+cast(Type, nil) when ?IS_NULL_TYPE(Type) ->
+  {ok, ?AVRO_VALUE(Type, null)};
 cast(Type, Value) when ?IS_BOOLEAN_TYPE(Type) andalso
                        is_boolean(Value) ->
   {ok, ?AVRO_VALUE(Type, Value)};

src/erlavro.app.src

@@ -1,7 +1,7 @@
 {application, erlavro,
   [
     {description, "Apache Avro support for Erlang/Elixir"},
-    {vsn, "2.8.1"},
+    {vsn, "2.8.2"},
     {registered, []},
     {applications, [
       kernel,

test/avro_tests.erl

@@ -411,6 +411,35 @@ default_values_test() ->
   TestFun([{encoding, avro_json}]),
   ok.
 
+nil_values_test() ->
+  File = filename:join(priv_dir(), "test.avsc"),
+  {ok, JSON} = file:read_file(File),
+  Type = avro:decode_schema(JSON),
+  Lkup = avro:make_lkup_fun(Type),
+  %% Encode input has no 'children' field, default value should be used
+  Input = [{"f1", [{"label", "x"}]}, {"f2", nil}, {"f3", nil}],
+  Expect = [{<<"f1">>, [ {<<"label">>, <<"x">>}
+                       , {<<"children">>,
+                          [ [ {<<"label">>, <<"default-label">>}
+                            , {<<"children">>, []}
+                            ]
+                          ]}
+                       ]},
+            {<<"f2">>, null},
+            {<<"f3">>, null}],
+  TestFun =
+    fun(Opts) ->
+      RootType = "org.apache.avro.test",
+      Encoder = avro:make_encoder(Lkup, Opts),
+      Decoder = avro:make_decoder(Lkup, Opts),
+      Encoded = Encoder(RootType, Input),
+      Decoded = Decoder(RootType, Encoded),
+      ?assertEqual(Expect, Decoded)
+    end,
+  TestFun([{encoding, avro_binary}]),
+  TestFun([{encoding, avro_json}]),
+  ok.
+
 default_values_with_map_type_test() ->
   File = filename:join(priv_dir(), "test.avsc"),
   {ok, JSON} = file:read_file(File),