Fix json-related bugs

include/datadog/null_collector.h

@@ -19,8 +19,8 @@ class NullCollector : public Collector {
   std::string config() const override {
     // clang-format off
     return R"({
-        {"type", "datadog::tracing::NullCollector"},
-        {"config", {}}
+        "type": "datadog::tracing::NullCollector",
+        "config": {}
     })";
     // clang-format on
   };

src/datadog/datadog_agent.cpp

@@ -254,8 +254,8 @@ std::string DatadogAgent::config() const {
       {"flush_interval_milliseconds", std::chrono::duration_cast<std::chrono::milliseconds>(flush_interval_).count() },
       {"request_timeout_milliseconds", std::chrono::duration_cast<std::chrono::milliseconds>(request_timeout_).count() },
       {"shutdown_timeout_milliseconds", std::chrono::duration_cast<std::chrono::milliseconds>(shutdown_timeout_).count() },
-      {"http_client", http_client_->config()},
-      {"event_scheduler", event_scheduler_->config()},
+      {"http_client", nlohmann::json::parse(http_client_->config())},
+      {"event_scheduler", nlohmann::json::parse(event_scheduler_->config())},
     })},
   }).dump();
   // clang-format on

src/datadog/span_sampler.cpp

@@ -73,9 +73,8 @@ nlohmann::json SpanSampler::config_json() const {
   }
 
   return nlohmann::json::object({
-                                    {"rules", rules},
-                                })
-      .dump();
+      {"rules", rules},
+  });
 }
 
 }  // namespace tracing

src/datadog/tracer.cpp

@@ -83,15 +83,27 @@ Tracer::Tracer(const FinalizedTracerConfig& config,
   }
 }
 
+namespace {
+template <typename T>
+std::vector<std::string> to_string_vec(const std::vector<T>& vec) {
+  std::vector<std::string> result{vec.size()};
+  result.reserve(vec.size());
+  std::transform(vec.begin(), vec.end(), result.begin(), [](const T& item) {
+    return std::string{to_string_view(item)};
+  });
+  return result;
+}
+}  // namespace
+
 std::string Tracer::config() const {
   // clang-format off
   auto config = nlohmann::json::object({
     {"version", tracer_version_string},
     {"runtime_id", runtime_id_.string()},
-    {"collector", collector_->config()},
+    {"collector", nlohmann::json::parse(collector_->config())},
     {"span_sampler", span_sampler_->config_json()},
-    {"injection_styles", join_propagation_styles(injection_styles_)},
-    {"extraction_styles", join_propagation_styles(extraction_styles_)},
+    {"injection_styles", to_string_vec(injection_styles_)},
+    {"extraction_styles", to_string_vec(extraction_styles_)},
     {"tags_header_size", tags_header_max_size_},
     {"environment_variables", environment::to_json()},
   });