FIX: Fix handling of null last_modified_date

Author: threecgreen

CHANGELOG.md

@@ -11,6 +11,8 @@
   - "ICE Futures Europe (Commodities)" renamed to "ICE Europe Commodities"
 
 ### Bug fixes
+- Fixed handling of `null` `last_modified_date` in `MetadataGetDatasetCondition`
+  response
 - Fixed default `ShouldLog` implementation
 
 ## 0.38.0 - 2025-06-10

include/databento/detail/json_helpers.hpp

@@ -4,6 +4,7 @@
 #include <nlohmann/json.hpp>
 
 #include <map>  // multimap
+#include <optional>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -79,6 +80,10 @@ template <>
 std::string ParseAt(std::string_view endpoint, const nlohmann::json& json,
                     std::string_view key);
 template <>
+std::optional<std::string> ParseAt(std::string_view endpoint,
+                                   const nlohmann::json& json,
+                                   std::string_view key);
+template <>
 std::uint64_t ParseAt(std::string_view endpoint, const nlohmann::json& json,
                       std::string_view key);
 template <>

include/databento/metadata.hpp

@@ -2,6 +2,7 @@
 
 #include <cstdint>
 #include <map>
+#include <optional>
 #include <ostream>
 #include <string>
 #include <unordered_map>
@@ -30,7 +31,7 @@ struct UnitPricesForMode {
 struct DatasetConditionDetail {
   std::string date;
   DatasetCondition condition;
-  std::string last_modified_date;
+  std::optional<std::string> last_modified_date;
 };
 
 struct DatasetRange {

src/detail/json_helpers.cpp

@@ -1,6 +1,7 @@
 #include "databento/detail/json_helpers.hpp"
 
 #include <numeric>  // accumulate
+#include <optional>
 #include <sstream>  // istringstream
 #include <string>
 
@@ -49,6 +50,17 @@ bool ParseAt(std::string_view endpoint, const nlohmann::json& json,
 template <>
 std::string ParseAt(std::string_view endpoint, const nlohmann::json& json,
                     std::string_view key) {
+  const auto s = ParseAt<std::optional<std::string>>(endpoint, json, key);
+  if (s) {
+    return *s;
+  }
+  return {};
+}
+
+template <>
+std::optional<std::string> ParseAt(std::string_view endpoint,
+                                   const nlohmann::json& json,
+                                   std::string_view key) {
   const auto& val_json = CheckedAt(endpoint, json, key);
   if (val_json.is_null()) {
     return {};

src/historical.cpp

@@ -520,12 +520,10 @@ Historical::MetadataGetDatasetCondition(const httplib::Params& params) {
     if (!detail_json.is_object()) {
       throw JsonResponseError::TypeMismatch(kEndpoint, "object", detail_json);
     }
-    std::string date =
-        detail::ParseAt<std::string>(kEndpoint, detail_json, "date");
-    const DatasetCondition condition =
-        detail::FromCheckedAtString<DatasetCondition>(kEndpoint, detail_json,
-                                                      "condition");
-    std::string last_modified_date = detail::ParseAt<std::string>(
+    auto date = detail::ParseAt<std::string>(kEndpoint, detail_json, "date");
+    const auto condition = detail::FromCheckedAtString<DatasetCondition>(
+        kEndpoint, detail_json, "condition");
+    auto last_modified_date = detail::ParseAt<std::optional<std::string>>(
         kEndpoint, detail_json, "last_modified_date");
     details.emplace_back(DatasetConditionDetail{std::move(date), condition,
                                                 std::move(last_modified_date)});

src/stream_op_helper.hpp

@@ -60,7 +60,7 @@ class StreamOpHelper {
   template <typename T>
   void FmtToStream(const std::optional<T>& val) {
     if (val.has_value()) {
-      stream_ << *val;
+      FmtToStream(*val);
     } else {
       stream_ << "nullopt";
     }

tests/src/historical_tests.cpp

@@ -10,6 +10,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <filesystem>
+#include <optional>
 #include <stdexcept>  // logic_error
 #include <utility>    // move
 
@@ -424,7 +425,7 @@ TEST_F(HistoricalTests, TestMetadataGetDatasetCondition) {
                               {"last_modified_date", "2023-03-01"}},
                              {{"date", "2022-11-10"},
                               {"condition", "missing"},
-                              {"last_modified_date", "2023-03-01"}}};
+                              {"last_modified_date", nullptr}}};
   mock_server_.MockGetJson("/v0/metadata.get_dataset_condition",
                            {{"dataset", dataset::kXnasItch},
                             {"start_date", "2022-11-06"},
@@ -440,7 +441,7 @@ TEST_F(HistoricalTests, TestMetadataGetDatasetCondition) {
       {"2022-11-07", DatasetCondition::Available, "2023-03-01"},
       {"2022-11-08", DatasetCondition::Degraded, "2023-03-01"},
       {"2022-11-09", DatasetCondition::Pending, "2023-03-01"},
-      {"2022-11-10", DatasetCondition::Missing, "2023-03-01"},
+      {"2022-11-10", DatasetCondition::Missing, std::nullopt},
   };
   EXPECT_EQ(res, kExp);
 }

tests/src/metadata_tests.cpp

@@ -5,11 +5,16 @@
 
 namespace databento::tests {
 TEST(MetadataTests, TestDatasetConditionDetailToString) {
-  const DatasetConditionDetail target{"2022-11-10", DatasetCondition::Available,
-                                      "2023-03-01"};
-  ASSERT_EQ(
-      ToString(target),
+  const DatasetConditionDetail available{
+      "2022-11-10", DatasetCondition::Available, "2023-03-01"};
+  EXPECT_EQ(
+      ToString(available),
       R"(DatasetConditionDetail { date = "2022-11-10", condition = available, last_modified_date = "2023-03-01" })");
+  const DatasetConditionDetail missing{
+      "2022-11-11", DatasetCondition::Missing, {}};
+  EXPECT_EQ(
+      ToString(missing),
+      R"(DatasetConditionDetail { date = "2022-11-11", condition = missing, last_modified_date = nullopt })");
 }
 
 TEST(MetadataTests, TestDatasetRangeToString) {