FIX: Fix encoding metadata changing version

Author: threecgreen

CHANGELOG.md

@@ -13,6 +13,9 @@
   `Metadata` is represented in other languages and removed the boolean
   `has_mixed_stype_in` and `has_mixed_schema` fields
 
+### Bug fixes
+- Fixed behavior where encoding metadata could lower the `version`
+
 ## 0.36.0 - 2025-05-27
 
 This version marks the release of DBN version 3 (DBNv3), which is the new default.

README.md

@@ -95,16 +95,17 @@ Here is a simple program that fetches 10 seconds of trades for all ES mini futur
 #include <databento/live.hpp>
 #include <databento/symbol_map.hpp>
 #include <iostream>
-#include <string>
 #include <thread>
 
 using namespace databento;
 
 int main() {
   PitSymbolMap symbol_mappings;
 
-  auto client =
-      LiveBuilder{}.SetKeyFromEnv().SetDataset("GLBX.MDP3").BuildThreaded();
+  auto client = LiveBuilder{}
+                    .SetKeyFromEnv()
+                    .SetDataset(Dataset::GlbxMdp3)
+                    .BuildThreaded();
 
   auto handler = [&symbol_mappings](const Record& rec) {
     symbol_mappings.OnRecord(rec);

examples/live/readme.cpp

@@ -5,16 +5,17 @@
 #include <databento/live.hpp>
 #include <databento/symbol_map.hpp>
 #include <iostream>
-#include <string>
 #include <thread>
 
 using namespace databento;
 
 int main() {
   PitSymbolMap symbol_mappings;
 
-  auto client =
-      LiveBuilder{}.SetKeyFromEnv().SetDataset("GLBX.MDP3").BuildThreaded();
+  auto client = LiveBuilder{}
+                    .SetKeyFromEnv()
+                    .SetDataset(Dataset::GlbxMdp3)
+                    .BuildThreaded();
 
   auto handler = [&symbol_mappings](const Record& rec) {
     symbol_mappings.OnRecord(rec);

examples/live/simple.cpp

@@ -23,13 +23,13 @@ int main() {
                     .SetLogReceiver(log_receiver.get())
                     .SetSendTsOut(true)
                     .SetKeyFromEnv()
-                    .SetDataset(databento::dataset::kGlbxMdp3)
+                    .SetDataset(databento::Dataset::GlbxMdp3)
                     .BuildThreaded();
 
   // Set up signal handler for Ctrl+C
   std::signal(SIGINT, [](int signal) { gSignal = signal; });
 
-  std::vector<std::string> symbols{"ESZ4", "ESZ4 C4200", "ESZ4 P4100"};
+  std::vector<std::string> symbols{"ESZ5", "ESZ5 C6200", "ESZ5 P5500"};
   client.Subscribe(symbols, databento::Schema::Definition,
                    databento::SType::RawSymbol);
   client.Subscribe(symbols, databento::Schema::Mbo,

src/dbn_encoder.cpp

@@ -87,8 +87,15 @@ DbnEncoder::DbnEncoder(const Metadata& metadata, IWritable* output)
 }
 
 void DbnEncoder::EncodeMetadata(const Metadata& metadata, IWritable* output) {
-  const auto version = std::min<std::uint8_t>(
-      std::max<std::uint8_t>(1, metadata.version), kDbnVersion);
+  if (metadata.version > kDbnVersion) {
+    throw databento::InvalidArgumentError{
+        "EncodeMetadata", "metadata",
+        "Can't encode Metadata with version " +
+            std::to_string(+metadata.version) +
+            " which is greater than the maximum supported version " +
+            std::to_string(+kDbnVersion)};
+  }
+  const auto version = std::max<std::uint8_t>(1, metadata.version);
   EncodeChars(kDbnPrefix, kMagicSize - 1, output);
   EncodeAsBytes(version, output);
   const auto [length, end_padding] = CalcLength(metadata);

tests/include/temp_file.hpp

@@ -3,7 +3,6 @@
 #include <gtest/gtest.h>  // EXPECT_EQ
 
 #include <cassert>  // assert
-#include <cstdio>   // remove
 #include <filesystem>
 #include <fstream>  // ifstream
 #include <string>
@@ -29,9 +28,8 @@ class TempFile {
   TempFile(TempFile&&) = default;
   TempFile& operator=(TempFile&&) = default;
   ~TempFile() {
-    const int ret = std::remove(path_.c_str());
-    EXPECT_EQ(ret, 0) << "TempFile couldn't remove file at " << path_ << ": "
-                      << ::strerror(errno);
+    const bool ret = std::filesystem::remove(path_);
+    EXPECT_TRUE(ret) << "TempFile at " << path_ << " did not exist";
   }
 
   const std::filesystem::path& Path() const { return path_; }

tests/src/dbn_encoder_tests.cpp

@@ -9,6 +9,7 @@
 #include "databento/dbn.hpp"
 #include "databento/dbn_decoder.hpp"
 #include "databento/dbn_encoder.hpp"
+#include "databento/exceptions.hpp"
 #include "databento/log.hpp"
 #include "mock/mock_io.hpp"
 
@@ -41,4 +42,25 @@ TEST(DbnEncoderTests, TestEncodeDecodeMetadataIdentity) {
   const auto res = decoder.DecodeMetadata();
   ASSERT_EQ(res, metadata);
 }
+
+TEST(DbnEncoderTests, TestEncodeNewerMetadataErrors) {
+  auto logger = std::make_unique<NullLogReceiver>();
+  const Metadata metadata{kDbnVersion + 1,
+                          dataset::kGlbxMdp3,
+                          Schema::Mbp10,
+                          {},
+                          UnixNanos{},
+                          0,
+                          SType::RawSymbol,
+                          SType::InstrumentId,
+                          true,
+                          kSymbolCstrLen,
+                          {},
+                          {},
+                          {},
+                          {}};
+  mock::MockIo io{};
+  ASSERT_THROW(DbnEncoder::EncodeMetadata(metadata, &io),
+               databento::InvalidArgumentError);
+}
 }  // namespace databento::tests