Made sure TaggedUnion can be used in combination with rfl::NoExtraFields; fixes #567 (#573)

Author: liuzicheng1987

include/rfl/parsing/Parser_tagged_union.hpp

@@ -154,18 +154,13 @@ struct Parser<R, W, TaggedUnion<_discriminator, AlternativeTypes...>,
         return Error(stream.str());
       };
 
-      if constexpr (no_field_names_) {
-        using T = tagged_union_wrapper_no_ptr_t<std::invoke_result_t<
-            decltype(wrap_if_necessary<AlternativeType>), AlternativeType>>;
-        *_result = Parser<R, W, T, ProcessorsType>::read(_r, _var)
-                       .transform(get_fields)
-                       .transform(to_tagged_union)
-                       .transform_error(embellish_error);
-      } else {
-        *_result = Parser<R, W, AlternativeType, ProcessorsType>::read(_r, _var)
-                       .transform(to_tagged_union)
-                       .transform_error(embellish_error);
-      }
+      using T = tagged_union_wrapper_no_ptr_t<std::invoke_result_t<
+          decltype(wrap_if_necessary<AlternativeType>), AlternativeType>>;
+
+      *_result = Parser<R, W, T, ProcessorsType>::read(_r, _var)
+                     .transform(get_fields)
+                     .transform(to_tagged_union)
+                     .transform_error(embellish_error);
 
       *_match_found = true;
     }

tests/json/test_tagged_union_with_no_extra_fields.cpp

@@ -0,0 +1,29 @@
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+
+#include "write_and_read.hpp"
+
+namespace test_tagged_union_with_no_extra_fields {
+
+struct Circle {
+  double radius;
+};
+
+struct Rectangle {
+  double height;
+  double width;
+};
+
+struct Square {
+  double width;
+};
+
+using Shapes = rfl::TaggedUnion<"shape", Circle, Square, Rectangle>;
+
+TEST(json, test_tagged_union_with_no_extra_fields) {
+  const Shapes r = Rectangle{.height = 10, .width = 5};
+
+  write_and_read<rfl::NoExtraFields>(
+      r, R"({"shape":"Rectangle","height":10.0,"width":5.0})");
+}
+}  // namespace test_tagged_union_with_no_extra_fields