fix: ensure x-launchdarkly-tags is sent in event requests (#145)

Moves application tag into HTTP Config, so it can propagate to data
sources + event sender.

Author: cwaldren-ld

libs/client-sdk/src/client_impl.cpp

@@ -34,7 +34,6 @@ using launchdarkly::config::shared::built::HttpProperties;
 
 static std::shared_ptr<IDataSource> MakeDataSource(
     HttpProperties const& http_properties,
-    std::optional<std::string> app_tags,
     Config const& config,
     Context const& context,
     boost::asio::any_io_executor const& executor,
@@ -48,11 +47,6 @@ static std::shared_ptr<IDataSource> MakeDataSource(
 
     auto builder = HttpPropertiesBuilder(http_properties);
 
-    // Event sources should include application tags.
-    if (app_tags) {
-        builder.Header("x-launchdarkly-tags", *app_tags);
-    }
-
     auto data_source_properties = builder.Build();
 
     if (config.DataSourceConfig().method.index() == 0) {
@@ -93,10 +87,12 @@ ClientImpl::ClientImpl(Config config,
                        Context context,
                        std::string const& version)
     : config_(config),
-      http_properties_(HttpPropertiesBuilder(config.HttpProperties())
-                           .Header("user-agent", "CPPClient/" + version)
-                           .Header("authorization", config.SdkKey())
-                           .Build()),
+      http_properties_(
+          HttpPropertiesBuilder(config.HttpProperties())
+              .Header("user-agent", "CPPClient/" + version)
+              .Header("authorization", config.SdkKey())
+              .Header("x-launchdarkly-tags", config.ApplicationTag())
+              .Build()),
       logger_(MakeLogger(config.Logging())),
       ioc_(kAsioConcurrencyHint),
       work_(boost::asio::make_work_guard(ioc_)),
@@ -106,10 +102,9 @@ ClientImpl::ClientImpl(Config config,
                     config.Persistence().max_contexts_,
                     MakePersistence(config)),
       data_source_factory_([this]() {
-          return MakeDataSource(http_properties_, config_.ApplicationTag(),
-                                config_, context_, ioc_.get_executor(),
-                                flag_manager_.Updater(), status_manager_,
-                                logger_);
+          return MakeDataSource(http_properties_, config_, context_,
+                                ioc_.get_executor(), flag_manager_.Updater(),
+                                status_manager_, logger_);
       }),
       data_source_(nullptr),
       event_processor_(nullptr),

libs/common/include/launchdarkly/config/shared/builders/http_properties_builder.hpp

@@ -2,6 +2,7 @@
 
 #include <chrono>
 #include <map>
+#include <optional>
 #include <string>
 #include <vector>
 
@@ -106,14 +107,14 @@ class HttpPropertiesBuilder {
         std::map<std::string, std::string> base_headers);
 
     /**
-     * Set a custom header value.
-     *
-     * Calling Headers will replace any previously set values.
-     * @param key The key for the header.
-     * @param value The header value.
+     * Set an optional header value. If the value is std::nullopt, any existing
+     * header by that name is removed.
+     * @param name The name of the header.
+     * @param value The optional header value.
      * @return A reference to this builder.
      */
-    HttpPropertiesBuilder& Header(std::string key, std::string value);
+    HttpPropertiesBuilder& Header(std::string key,
+                                  std::optional<std::string> value);
 
     /**
      * Build a set of HttpProperties.

libs/common/src/config/http_properties_builder.cpp

@@ -72,8 +72,12 @@ HttpPropertiesBuilder<SDK>& HttpPropertiesBuilder<SDK>::Headers(
 template <typename SDK>
 HttpPropertiesBuilder<SDK>& HttpPropertiesBuilder<SDK>::Header(
     std::string key,
-    std::string value) {
-    base_headers_.insert_or_assign(key, value);
+    std::optional<std::string> value) {
+    if (value) {
+        base_headers_.insert_or_assign(key, *value);
+    } else {
+        base_headers_.erase(key);
+    }
     return *this;
 }