add ToJsonString to avoid include nlohmann/json.hpp

Author: xiao.dong

src/iceberg/json_internal.cc

@@ -309,6 +309,10 @@ nlohmann::json ToJson(const Schema& schema) {
   return json;
 }
 
+Result<std::string> ToJsonString(const Schema& schema) {
+  return ToJsonString(ToJson(schema));
+}
+
 nlohmann::json ToJson(const SnapshotRef& ref) {
   nlohmann::json json;
   json[kSnapshotId] = ref.snapshot_id;
@@ -490,6 +494,10 @@ nlohmann::json ToJson(const PartitionSpec& partition_spec) {
   return json;
 }
 
+Result<std::string> ToJsonString(const PartitionSpec& partition_spec) {
+  return ToJsonString(ToJson(partition_spec));
+}
+
 Result<std::unique_ptr<PartitionField>> PartitionFieldFromJson(
     const nlohmann::json& json, bool allow_field_id_missing) {
   ICEBERG_ASSIGN_OR_RAISE(auto source_id, GetJsonValue<int32_t>(json, kSourceId));
@@ -785,6 +793,10 @@ nlohmann::json ToJson(const TableMetadata& table_metadata) {
   return json;
 }
 
+Result<std::string> ToJsonString(const TableMetadata& table_metadata) {
+  return ToJsonString(ToJson(table_metadata));
+}
+
 namespace {
 
 /// \brief Parse the schemas from the JSON object.

src/iceberg/json_internal.h

@@ -80,6 +80,12 @@ ICEBERG_EXPORT Result<std::unique_ptr<SortOrder>> SortOrderFromJson(
 /// \return The JSON representation of the schema.
 ICEBERG_EXPORT nlohmann::json ToJson(const Schema& schema);
 
+/// \brief Convert an Iceberg Schema to JSON.
+///
+/// \param[in] schema The Iceberg schema to convert.
+/// \return The JSON string of the schema.
+ICEBERG_EXPORT Result<std::string> ToJsonString(const Schema& schema);
+
 /// \brief Convert JSON to an Iceberg Schema.
 ///
 /// \param[in] json The JSON representation of the schema.
@@ -148,6 +154,18 @@ ICEBERG_EXPORT Result<std::unique_ptr<PartitionField>> PartitionFieldFromJson(
 /// array.
 ICEBERG_EXPORT nlohmann::json ToJson(const PartitionSpec& partition_spec);
 
+/// \brief Serializes a `PartitionSpec` object to JSON.
+///
+/// This function converts a `PartitionSpec` object into a JSON representation.
+/// The resulting JSON includes the spec ID and a list of `PartitionField` objects.
+/// Each `PartitionField` is serialized as described in the `ToJson(PartitionField)`
+/// function.
+///
+/// \param partition_spec The `PartitionSpec` object to be serialized.
+/// \return A JSON string of the `PartitionSpec` with its order ID and fields
+/// array.
+ICEBERG_EXPORT Result<std::string> ToJsonString(const PartitionSpec& partition_spec);
+
 /// \brief Deserializes a JSON object into a `PartitionSpec` object.
 ///
 /// This function parses the provided JSON and creates a `PartitionSpec` object.
@@ -246,6 +264,12 @@ ICEBERG_EXPORT Result<MetadataLogEntry> MetadataLogEntryFromJson(
 /// \return A JSON object representing the `TableMetadata`.
 ICEBERG_EXPORT nlohmann::json ToJson(const TableMetadata& table_metadata);
 
+/// \brief Serializes a `TableMetadata` object to JSON.
+///
+/// \param table_metadata The `TableMetadata` object to be serialized.
+/// \return A JSON string of the `TableMetadata`.
+ICEBERG_EXPORT Result<std::string> ToJsonString(const TableMetadata& table_metadata);
+
 /// \brief Deserializes a JSON object into a `TableMetadata` object.
 ///
 /// \param json The JSON object representing a `TableMetadata`.

src/iceberg/test/metadata_io_test.cc

@@ -90,8 +90,7 @@ TEST_F(MetadataIOTest, ReadWriteMetadata) {
 TEST_F(MetadataIOTest, ReadWriteCompressedMetadata) {
   TableMetadata metadata = PrepareMetadata();
 
-  auto json = ToJson(metadata);
-  auto ret = ToJsonString(json);
+  auto ret = ToJsonString(metadata);
   ASSERT_TRUE(ret.has_value());
   auto json_string = ret.value();
 

src/iceberg/v1_metadata.cc

@@ -19,8 +19,6 @@
 
 #include "iceberg/v1_metadata.h"
 
-#include <nlohmann/json.hpp>
-
 #include "iceberg/json_internal.h"
 #include "iceberg/manifest_entry.h"
 #include "iceberg/manifest_list.h"
@@ -51,9 +49,9 @@ Status ManifestEntryAdapterV1::Init() {
       DataFile::kSortOrderId.field_id(),
   };
   ICEBERG_RETURN_UNEXPECTED(InitSchema(kManifestEntryFieldIds));
-  metadata_["schema"] = ToJson(*manifest_schema_).dump();
+  ICEBERG_ASSIGN_OR_RAISE(metadata_["schema"], ToJsonString(*manifest_schema_))
   if (partition_spec_ != nullptr) {
-    metadata_["partition-spec"] = ToJson(*partition_spec_).dump();
+    ICEBERG_ASSIGN_OR_RAISE(metadata_["partition-spec"], ToJsonString(*partition_spec_));
     metadata_["partition-spec-id"] = std::to_string(partition_spec_->spec_id());
   }
   metadata_["format-version"] = "1";

src/iceberg/v2_metadata.cc

@@ -19,8 +19,6 @@
 
 #include "iceberg/v2_metadata.h"
 
-#include <nlohmann/json.hpp>
-
 #include "iceberg/json_internal.h"
 #include "iceberg/manifest_entry.h"
 #include "iceberg/manifest_list.h"
@@ -55,9 +53,9 @@ Status ManifestEntryAdapterV2::Init() {
       DataFile::kReferencedDataFile.field_id(),
   };
   ICEBERG_RETURN_UNEXPECTED(InitSchema(kManifestEntryFieldIds));
-  metadata_["schema"] = ToJson(*manifest_schema_).dump();
+  ICEBERG_ASSIGN_OR_RAISE(metadata_["schema"], ToJsonString(*manifest_schema_))
   if (partition_spec_ != nullptr) {
-    metadata_["partition-spec"] = ToJson(*partition_spec_).dump();
+    ICEBERG_ASSIGN_OR_RAISE(metadata_["partition-spec"], ToJsonString(*partition_spec_));
     metadata_["partition-spec-id"] = std::to_string(partition_spec_->spec_id());
   }
   metadata_["format-version"] = "2";

src/iceberg/v3_metadata.cc

@@ -19,8 +19,6 @@
 
 #include "iceberg/v3_metadata.h"
 
-#include <nlohmann/json.hpp>
-
 #include "iceberg/json_internal.h"
 #include "iceberg/manifest_entry.h"
 #include "iceberg/manifest_list.h"
@@ -58,9 +56,9 @@ Status ManifestEntryAdapterV3::Init() {
       DataFile::kContentSize.field_id(),
   };
   ICEBERG_RETURN_UNEXPECTED(InitSchema(kManifestEntryFieldIds));
-  metadata_["schema"] = ToJson(*manifest_schema_).dump();
+  ICEBERG_ASSIGN_OR_RAISE(metadata_["schema"], ToJsonString(*manifest_schema_))
   if (partition_spec_ != nullptr) {
-    metadata_["partition-spec"] = ToJson(*partition_spec_).dump();
+    ICEBERG_ASSIGN_OR_RAISE(metadata_["partition-spec"], ToJsonString(*partition_spec_));
     metadata_["partition-spec-id"] = std::to_string(partition_spec_->spec_id());
   }
   metadata_["format-version"] = "3";