fix: Ensure that serialization of a variation or rollout uses the correct overload.

Author: kinyoklion

libs/internal/include/launchdarkly/serialization/json_flag.hpp

@@ -7,6 +7,9 @@
 
 namespace launchdarkly {
 
+struct VariationOrRolloutContext {};
+
+
 tl::expected<std::optional<data_model::Flag::Rollout>, JsonError> tag_invoke(
     boost::json::value_to_tag<
         tl::expected<std::optional<data_model::Flag::Rollout>,
@@ -72,7 +75,7 @@ void tag_invoke(boost::json::value_from_tag const& unused,
 void tag_invoke(
     boost::json::value_from_tag const& unused,
     boost::json::value& json_value,
-    data_model::Flag::VariationOrRollout const& variation_or_rollout);
+    data_model::Flag::VariationOrRollout const& variation_or_rollout, const VariationOrRolloutContext&);
 
 void tag_invoke(
     boost::json::value_from_tag const& unused,

libs/internal/include/launchdarkly/serialization/value_mapping.hpp

@@ -189,6 +189,16 @@ void WriteMinimal(boost::json::object& obj,
     }
 }
 
+template <typename T, typename C>
+void WriteMinimal(boost::json::object& obj,
+                  std::string const& key,
+                  T const& val,
+                  std::function<bool()> const& predicate, const C &c) {
+    if (predicate()) {
+        obj.emplace(key, boost::json::value_from(val, c));
+    }
+}
+
 void WriteMinimal(boost::json::object& obj,
                   std::string const& key,  // No copy when not used.
                   bool val);

libs/internal/src/serialization/json_flag.cpp

@@ -255,7 +255,7 @@ void tag_invoke(boost::json::value_from_tag const& unused,
 void tag_invoke(
     boost::json::value_from_tag const& unused,
     boost::json::value& json_value,
-    data_model::Flag::VariationOrRollout const& variation_or_rollout) {
+    data_model::Flag::VariationOrRollout const& variation_or_rollout, const VariationOrRolloutContext&) {
     auto& obj = json_value.emplace_object();
     std::visit(
         [&obj](auto&& arg) {
@@ -364,7 +364,7 @@ void tag_invoke(boost::json::value_from_tag const& unused,
                 }
             },
             flag.fallthrough);
-    });
+    }, VariationOrRolloutContext());
     WriteMinimal(obj, "clientSideAvailability", flag.clientSideAvailability,
                  [&]() {
                      return flag.clientSideAvailability.usingEnvironmentId ||

libs/internal/tests/data_model_serialization_test.cpp

@@ -423,7 +423,7 @@ TEST(RolloutTests, SerializeAllFields) {
 TEST(VariationOrRolloutTests, SerializeVariation) {
     data_model::Flag::VariationOrRollout variation = 5;
 
-    auto json = boost::json::value_from(variation);
+    auto json = boost::json::value_from(variation, VariationOrRolloutContext());
 
     auto expected = boost::json::parse(R"({"variation":5})");
     EXPECT_EQ(expected, json);
@@ -438,8 +438,9 @@ TEST(VariationOrRolloutTests, SerializeRollout) {
     rollout.seed = 42;
     rollout.variations = {
         data_model::Flag::Rollout::WeightedVariation::Untracked(1, 2), {3, 4}};
-    data_model::Flag::VariationOrRollout var_or_roll = rollout;
-    auto json = boost::json::value_from(var_or_roll);
+    data_model::Flag::VariationOrRollout var_or_roll;
+    var_or_roll.emplace<Rollout>(rollout);
+    auto json = boost::json::value_from(var_or_roll, VariationOrRolloutContext());
 
     auto expected = boost::json::parse(R"({
     "rollout":{