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merged 1 commit into from
Oct 2, 2025
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refactor: extract JSON utilities for code reuse #249

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180 changes: 1 addition & 179 deletions src/iceberg/json_internal.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,7 @@
#include "iceberg/transform.h"
#include "iceberg/type.h"
#include "iceberg/util/formatter.h" // IWYU pragma: keep
#include "iceberg/util/json_util_internal.h"
#include "iceberg/util/macros.h"
#include "iceberg/util/timepoint.h"

Expand Down Expand Up @@ -166,185 +167,6 @@ constexpr std::string_view kFileSizeInBytes = "file-size-in-bytes";
constexpr std::string_view kFileFooterSizeInBytes = "file-footer-size-in-bytes";
constexpr std::string_view kBlobMetadata = "blob-metadata";

template <typename T>
void SetOptionalField(nlohmann::json& json, std::string_view key,
const std::optional<T>& value) {
if (value.has_value()) {
json[key] = *value;
}
}

std::string SafeDumpJson(const nlohmann::json& json) {
return json.dump(/*indent=*/-1, /*indent_char=*/' ', /*ensure_ascii=*/false,
nlohmann::detail::error_handler_t::ignore);
}

template <typename T>
Result<T> GetJsonValueImpl(const nlohmann::json& json, std::string_view key) {
try {
return json.at(key).get<T>();
} catch (const std::exception& ex) {
return JsonParseError("Failed to parse '{}' from {}: {}", key, SafeDumpJson(json),
ex.what());
}
}

template <typename T>
Result<std::optional<T>> GetJsonValueOptional(const nlohmann::json& json,
std::string_view key) {
if (!json.contains(key)) {
return std::nullopt;
}
return GetJsonValueImpl<T>(json, key);
}

template <typename T>
Result<T> GetJsonValue(const nlohmann::json& json, std::string_view key) {
if (!json.contains(key)) {
return JsonParseError("Missing '{}' in {}", key, SafeDumpJson(json));
}
return GetJsonValueImpl<T>(json, key);
}

template <typename T>
Result<T> GetJsonValueOrDefault(const nlohmann::json& json, std::string_view key,
T default_value = T{}) {
if (!json.contains(key)) {
return default_value;
}
return GetJsonValueImpl<T>(json, key);
}

/// \brief Convert a list of items to a json array.
///
/// Note that ToJson(const T&) is required for this function to work.
template <typename T>
nlohmann::json::array_t ToJsonList(const std::vector<T>& list) {
return std::accumulate(list.cbegin(), list.cend(), nlohmann::json::array(),
[](nlohmann::json::array_t arr, const T& item) {
arr.push_back(ToJson(item));
return arr;
});
}

/// \brief Overload of the above function for a list of shared pointers.
template <typename T>
nlohmann::json::array_t ToJsonList(const std::vector<std::shared_ptr<T>>& list) {
return std::accumulate(list.cbegin(), list.cend(), nlohmann::json::array(),
[](nlohmann::json::array_t arr, const std::shared_ptr<T>& item) {
arr.push_back(ToJson(*item));
return arr;
});
}

/// \brief Parse a list of items from a JSON object.
///
/// \param[in] json The JSON object to parse.
/// \param[in] key The key to parse.
/// \param[in] from_json The function to parse an item from a JSON object.
/// \return The list of items.
template <typename T>
Result<std::vector<T>> FromJsonList(
const nlohmann::json& json, std::string_view key,
const std::function<Result<T>(const nlohmann::json&)>& from_json) {
std::vector<T> list{};
if (json.contains(key)) {
ICEBERG_ASSIGN_OR_RAISE(auto list_json, GetJsonValue<nlohmann::json>(json, key));
if (!list_json.is_array()) {
return JsonParseError("Cannot parse '{}' from non-array: {}", key,
SafeDumpJson(list_json));
}
for (const auto& entry_json : list_json) {
ICEBERG_ASSIGN_OR_RAISE(auto entry, from_json(entry_json));
list.emplace_back(std::move(entry));
}
}
return list;
}

/// \brief Parse a list of items from a JSON object.
///
/// \param[in] json The JSON object to parse.
/// \param[in] key The key to parse.
/// \param[in] from_json The function to parse an item from a JSON object.
/// \return The list of items.
template <typename T>
Result<std::vector<std::shared_ptr<T>>> FromJsonList(
const nlohmann::json& json, std::string_view key,
const std::function<Result<std::shared_ptr<T>>(const nlohmann::json&)>& from_json) {
std::vector<std::shared_ptr<T>> list{};
if (json.contains(key)) {
ICEBERG_ASSIGN_OR_RAISE(auto list_json, GetJsonValue<nlohmann::json>(json, key));
if (!list_json.is_array()) {
return JsonParseError("Cannot parse '{}' from non-array: {}", key,
SafeDumpJson(list_json));
}
for (const auto& entry_json : list_json) {
ICEBERG_ASSIGN_OR_RAISE(auto entry, from_json(entry_json));
list.emplace_back(std::move(entry));
}
}
return list;
}

/// \brief Convert a map of type <std::string, T> to a json object.
///
/// Note that ToJson(const T&) is required for this function to work.
template <typename T>
nlohmann::json::object_t ToJsonMap(const std::unordered_map<std::string, T>& map) {
return std::accumulate(map.cbegin(), map.cend(), nlohmann::json::object(),
[](nlohmann::json::object_t obj, const auto& item) {
obj[item.first] = ToJson(item.second);
return obj;
});
}

/// \brief Overload of the above function for a map of type <std::string,
/// std::shared_ptr<T>>.
template <typename T>
nlohmann::json::object_t ToJsonMap(
const std::unordered_map<std::string, std::shared_ptr<T>>& map) {
return std::accumulate(map.cbegin(), map.cend(), nlohmann::json::object(),
[](nlohmann::json::object_t obj, const auto& item) {
obj[item.first] = ToJson(*item.second);
return obj;
});
}

/// \brief Parse a map of type <std::string, T> from a JSON object.
///
/// \param[in] json The JSON object to parse.
/// \param[in] key The key to parse.
/// \param[in] from_json The function to parse an item from a JSON object.
/// \return The map of items.
template <typename T = std::string>
Result<std::unordered_map<std::string, T>> FromJsonMap(
const nlohmann::json& json, std::string_view key,
const std::function<Result<T>(const nlohmann::json&)>& from_json =
[](const nlohmann::json& json) -> Result<T> {
static_assert(std::is_same_v<T, std::string>, "T must be std::string");
try {
return json.get<std::string>();
} catch (const std::exception& ex) {
return JsonParseError("Cannot parse {} to a string value: {}", SafeDumpJson(json),
ex.what());
}
}) {
std::unordered_map<std::string, T> map{};
if (json.contains(key)) {
ICEBERG_ASSIGN_OR_RAISE(auto map_json, GetJsonValue<nlohmann::json>(json, key));
if (!map_json.is_object()) {
return JsonParseError("Cannot parse '{}' from non-object: {}", key,
SafeDumpJson(map_json));
}
for (const auto& [key, value] : map_json.items()) {
ICEBERG_ASSIGN_OR_RAISE(auto entry, from_json(value));
map[key] = std::move(entry);
}
}
return map;
}

} // namespace

nlohmann::json ToJson(const SortField& sort_field) {
Expand Down
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