Merge pull request #130 from zmstone/allow-empty-union

Allow empty union

Author: mikpe

changelog.md

@@ -1,3 +1,5 @@
+* 2.10.3
+   - Allow union type to have zero member types.
 * 2.10.2
    - Fix bytes and fixed JSON value decode
 * 2.10.1

src/avro_union.erl

@@ -54,8 +54,8 @@
 
 -include("avro_internal.hrl").
 
--type id2type() :: gb_trees:tree(union_index(), type_or_name()).
--type name2id() :: gb_trees:tree(name(), {union_index(), boolean()}).
+-type id2type() :: #{union_index() => type_or_name()}.
+-type name2id() :: #{name() => {union_index(), boolean()}}.
 -type encode_result() :: avro_binary() | avro_json().
 -type encode_fun() :: fun((avro_type(), avro:in(),
                            union_index()) -> encode_result()).
@@ -64,13 +64,15 @@
 
 %% @doc Define a union type.
 %% Exception when any of the below constraints is violated:
-%% 1. A union should have at least one member and no duplication
-%% 2. Union should no have union as direct member
-%% 3. No duplicated types are allowed in members
+%% 1. Union should no have union as direct member
+%% 2. No duplicated types are allowed in members
 %% @end
 -spec type([type_or_name()]) -> union_type() | no_return().
 type([]) ->
-  erlang:error(<<"union should have at least one member type">>);
+  #avro_union_type
+  { id2type = #{}
+  , name2id = #{}
+  };
 type([_ | _ ] = Types0) ->
   IsUnion = fun(T) -> ?IS_UNION_TYPE(T) end,
   lists:any(IsUnion, Types0) andalso
@@ -81,8 +83,8 @@ type([_ | _ ] = Types0) ->
   Name2Id = build_name_to_id(IndexedTypes),
   ok = assert_no_duplicated_names(Name2Id, []),
   #avro_union_type
-  { id2type = gb_trees:from_orddict(IndexedTypes)
-  , name2id = gb_trees:from_orddict(orddict:from_list(Name2Id))
+  { id2type = maps:from_list(IndexedTypes)
+  , name2id = maps:from_list(Name2Id)
   }.
 
 %% @doc Resolve fullname by newly discovered enclosing namespace.
@@ -103,17 +105,14 @@ update_member_types(T0, F) ->
 %% @doc Get the union member types in a list.
 -spec get_types(union_type()) -> [avro_type()].
 get_types(#avro_union_type{id2type = IndexedTypes}) ->
-  {_Ids, Types} = lists:unzip(gb_trees:to_list(IndexedTypes)),
+  {_Ids, Types} = lists:unzip(lists:keysort(1, maps:to_list(IndexedTypes))),
   Types.
 
 %% @doc Search for a union member by its index or full name.
 -spec lookup_type(name_raw() | union_index(), union_type()) ->
         {ok, avro_type() | name()} | false.
 lookup_type(Id, #avro_union_type{id2type = Types}) when is_integer(Id) ->
-  case gb_trees:lookup(Id, Types) of
-    {value, Type} -> {ok, Type};
-    none          -> false
-  end;
+  maps:is_key(Id, Types) andalso {ok, maps:get(Id, Types)};
 lookup_type(Name, Union) when ?IS_NAME(Name) ->
   case lookup_index(Name, Union) of
     {ok, {_Id, true}} -> {ok, avro:name2type(Name)};
@@ -241,10 +240,7 @@ try_encode_union_loop(UnionType, [MemberT | Rest], Value, Index, EncodeFun) ->
 -spec lookup_index(name(), union_type()) ->
         {ok, {union_index(), boolean()}} | false.
 lookup_index(Name, #avro_union_type{name2id = Ids}) when ?IS_NAME_RAW(Name) ->
-  case gb_trees:lookup(?NAME(Name), Ids) of
-    {value, Id} -> {ok, Id};
-    none        -> false
-  end.
+  maps:is_key(?NAME(Name), Ids) andalso {ok, maps:get(?NAME(Name), Ids)}.
 
 %% @private
 -spec do_cast(union_type(), {name(), avro_value()} | avro:in()) ->

test/avro_ocf_tests.erl

@@ -172,7 +172,7 @@ decoder_hook_test() ->
   ?assertEqual([[{<<"f1">>, 1}, {<<"f2">>, <<"modifiedNull">>}]], Objs).
 
 test_data(FileName) ->
-  filename:join([code:lib_dir(erlavro, test), "data", FileName]).
+  filename:join([code:lib_dir(erlavro), "test", "data", FileName]).
 
 %%%_* Emacs ====================================================================
 %%% Local Variables:

test/avro_schema_store_tests.erl

@@ -216,7 +216,7 @@ flat_test_record() ->
     ]).
 
 test_data(FileName) ->
-  filename:join([code:lib_dir(erlavro, test), "data", FileName]).
+  filename:join([code:lib_dir(erlavro), "test", "data", FileName]).
 
 define_field(Name, Type) -> avro_record:define_field(Name, Type).
 

test/avro_tests.erl

@@ -531,7 +531,7 @@ default_values_with_map_type_test() ->
   ok.
 
 test_data(FileName) ->
-  filename:join([code:lib_dir(erlavro, test), "data", FileName]).
+  filename:join([code:lib_dir(erlavro), "test", "data", FileName]).
 
 %%%_* Emacs ====================================================================
 %%% Local Variables:

test/avro_union_tests.erl

@@ -79,10 +79,6 @@ to_term_test() ->
   ?assertEqual(null, avro:to_term(Value1)),
   ?assertEqual(1,    avro:to_term(Value2)).
 
-empty_unon_not_allowed_test() ->
-  ?assertException(error, <<"union should have at least one member type">>,
-                   avro_union:type([])).
-
 cast_test() ->
   Type = avro_union:type([null, long]),
   ?assertMatch({ok, #avro_value{}}, avro_union:cast(Type, {long, 1})),
@@ -158,6 +154,11 @@ union_of_string_and_int_array_test() ->
                avro_union:encode(Union, <<"abc">>, StringEncodeFun)),
   ok.
 
+no_member_test() ->
+  Union = avro_union:type([]),
+  F = fun(_StringType, _StringValue, 0) -> error(unexpected) end,
+  ?assertError({unknown_member, _, string}, avro_union:encode(Union, {string, "abc"}, F)).
+
 %%%_* Emacs ====================================================================
 %%% Local Variables:
 %%% allout-layout: t