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fix: Ensure that serialization of a variation or rollout uses the correct overload. #483

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Merged
kinyoklion merged 6 commits into from
Oct 10, 2025
Merged

fix: Ensure that serialization of a variation or rollout uses the correct overload. #483

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df91388
fix: Ensure that serialization of a variation or rollout uses the cor…
kinyoklion Oct 8, 2025
24b2629
Add conditional compilation.
kinyoklion Oct 8, 2025
fd3bd44
Conditional boost code in tests.
kinyoklion Oct 8, 2025
5ad90f6
Fix typo
kinyoklion Oct 8, 2025
813a37c
Support both signatures for tag_invoke
kinyoklion Oct 8, 2025
aa1250c
Merge branch 'main' into rlamb/disambiguate-sequence-boost-json
kinyoklion Oct 9, 2025
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8 changes: 8 additions & 0 deletions libs/internal/include/launchdarkly/serialization/json_flag.hpp
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Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
#pragma once

#include <launchdarkly/data_model/flag.hpp>
Expand All @@ -7,6 +7,9 @@

namespace launchdarkly {

struct VariationOrRolloutContext {};
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@kinyoklion kinyoklion Oct 8, 2025

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This is effectively a "tag" which can be used as a discriminator.



tl::expected<std::optional<data_model::Flag::Rollout>, JsonError> tag_invoke(
boost::json::value_to_tag<
tl::expected<std::optional<data_model::Flag::Rollout>,
Expand Down Expand Up @@ -69,6 +72,11 @@
boost::json::value& json_value,
data_model::Flag::Rollout const& rollout);

void tag_invoke(
boost::json::value_from_tag const& unused,
boost::json::value& json_value,
data_model::Flag::VariationOrRollout const& variation_or_rollout, const VariationOrRolloutContext&);

void tag_invoke(
boost::json::value_from_tag const& unused,
boost::json::value& json_value,
Expand Down
20 changes: 20 additions & 0 deletions libs/internal/include/launchdarkly/serialization/value_mapping.hpp
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Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
#pragma once

#include <launchdarkly/detail/serialization/json_primitives.hpp>
Expand All @@ -5,6 +5,7 @@
#include <boost/core/ignore_unused.hpp>
#include <boost/json.hpp>
#include <tl/expected.hpp>
#include <boost/version.hpp>

#include <optional>
#include <type_traits>
Expand Down Expand Up @@ -189,6 +190,25 @@
}
}

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()) {
// In Boost 1.83 the ability to have a conversion context was added.
// It also introduces the potential for the wrong conversion to be used,
// so for boost 1.83 and greater we use a conversion context to ensure
// the correct serialization is used.
#if BOOST_VERSION >= 108300
obj.emplace(key, boost::json::value_from(val, c));
#else
boost::ignore_unused(c);
obj.emplace(key, boost::json::value_from(val));
#endif
}
}

void WriteMinimal(boost::json::object& obj,
std::string const& key, // No copy when not used.
bool val);
Expand Down
11 changes: 9 additions & 2 deletions libs/internal/src/serialization/json_flag.cpp
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Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
#include <boost/json.hpp>
#include <launchdarkly/serialization/json_context_aware_reference.hpp>
#include <launchdarkly/serialization/json_flag.hpp>
Expand Down Expand Up @@ -255,7 +255,7 @@
void tag_invoke(
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@kinyoklion kinyoklion Oct 8, 2025

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When the situation arose this function was not getting called for serialization. Instead the standard handling for std::variant was being called. This resulted in the value being directly serialized. So for example 42 instead of {variant: 42}. This would only happen for fallthrough. A rule directly serializes the value into a root field.

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) {
Expand All @@ -273,6 +273,13 @@
variation_or_rollout);
}

void tag_invoke(
boost::json::value_from_tag const& unused,
boost::json::value& json_value,
data_model::Flag::VariationOrRollout const& variation_or_rollout) {
tag_invoke(unused, json_value, variation_or_rollout, VariationOrRolloutContext());
}

void tag_invoke(boost::json::value_from_tag const& unused,
boost::json::value& json_value,
data_model::Flag::Prerequisite const& prerequisite) {
Expand Down Expand Up @@ -364,7 +371,7 @@
}
},
flag.fallthrough);
});
}, VariationOrRolloutContext());
WriteMinimal(obj, "clientSideAvailability", flag.clientSideAvailability,
[&]() {
return flag.clientSideAvailability.usingEnvironmentId ||
Expand Down
16 changes: 14 additions & 2 deletions libs/internal/tests/data_model_serialization_test.cpp
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Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
#include <gtest/gtest.h>

#include <boost/json/value_from.hpp>
Expand Down Expand Up @@ -423,8 +423,13 @@
TEST(VariationOrRolloutTests, SerializeVariation) {
data_model::Flag::VariationOrRollout variation = 5;

auto json = boost::json::value_from(variation);

//Explanation in value_mapping.hpp.
#if BOOST_VERSION >= 108300
auto json = boost::json::value_from(variation, VariationOrRolloutContext());
#else
auto json = boost::json::value_from(variation);
#endif
auto expected = boost::json::parse(R"({"variation":5})");
EXPECT_EQ(expected, json);
}
Expand All @@ -438,8 +443,15 @@
rollout.seed = 42;
rollout.variations = {
data_model::Flag::Rollout::WeightedVariation::Untracked(1, 2), {3, 4}};
data_model::Flag::VariationOrRollout var_or_roll = rollout;
data_model::Flag::VariationOrRollout var_or_roll;
var_or_roll.emplace<Rollout>(rollout);
//Explanation in value_mapping.hpp.
#if BOOST_VERSION >= 108300
auto json = boost::json::value_from(var_or_roll, VariationOrRolloutContext());
#else
auto json = boost::json::value_from(var_or_roll);
#endif


auto expected = boost::json::parse(R"({
"rollout":{
Expand Down
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