From 78e19d66d35bfbbbe350b49a09ec9e2645c478f2 Mon Sep 17 00:00:00 2001
From: gabime <gmelman1@gmail.com>
Date: Thu, 8 May 2025 15:33:08 +0300
Subject: [PATCH] Add register_or_replace(logger) to atomically replace logger
 in registry

---
 include/spdlog/details/registry-inl.h | 11 ++++++++++-
 include/spdlog/details/registry.h     |  2 ++
 include/spdlog/spdlog-inl.h           |  4 ++++
 include/spdlog/spdlog.h               |  5 +++++
 tests/test_registry.cpp               | 12 ++++++++++++
 5 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/include/spdlog/details/registry-inl.h b/include/spdlog/details/registry-inl.h
index f447848e..4cbdeb75 100644
--- a/include/spdlog/details/registry-inl.h
+++ b/include/spdlog/details/registry-inl.h
@@ -54,6 +54,11 @@ SPDLOG_INLINE void registry::register_logger(std::shared_ptr<logger> new_logger)
     register_logger_(std::move(new_logger));
 }
 
+SPDLOG_INLINE void registry::register_or_replace(std::shared_ptr<logger> new_logger) {
+    std::lock_guard<std::mutex> lock(logger_map_mutex_);
+    register_or_replace_(std::move(new_logger));
+}
+
 SPDLOG_INLINE void registry::initialize_logger(std::shared_ptr<logger> new_logger) {
     std::lock_guard<std::mutex> lock(logger_map_mutex_);
     new_logger->set_formatter(formatter_->clone());
@@ -252,10 +257,14 @@ SPDLOG_INLINE void registry::throw_if_exists_(const std::string &logger_name) {
 }
 
 SPDLOG_INLINE void registry::register_logger_(std::shared_ptr<logger> new_logger) {
-    auto logger_name = new_logger->name();
+    auto &logger_name = new_logger->name();
     throw_if_exists_(logger_name);
     loggers_[logger_name] = std::move(new_logger);
 }
 
+SPDLOG_INLINE void registry::register_or_replace_(std::shared_ptr<logger> new_logger) {
+    loggers_[new_logger->name()] = std::move(new_logger);
+}
+
 }  // namespace details
 }  // namespace spdlog
diff --git a/include/spdlog/details/registry.h b/include/spdlog/details/registry.h
index 8afcbd6f..72c70b82 100644
--- a/include/spdlog/details/registry.h
+++ b/include/spdlog/details/registry.h
@@ -31,6 +31,7 @@ public:
     registry &operator=(const registry &) = delete;
 
     void register_logger(std::shared_ptr<logger> new_logger);
+    void register_or_replace(std::shared_ptr<logger> new_logger);
     void initialize_logger(std::shared_ptr<logger> new_logger);
     std::shared_ptr<logger> get(const std::string &logger_name);
     std::shared_ptr<logger> default_logger();
@@ -105,6 +106,7 @@ private:
 
     void throw_if_exists_(const std::string &logger_name);
     void register_logger_(std::shared_ptr<logger> new_logger);
+    void register_or_replace_(std::shared_ptr<logger> new_logger);
     bool set_level_from_cfg_(logger *logger);
     std::mutex logger_map_mutex_, flusher_mutex_;
     std::recursive_mutex tp_mutex_;
diff --git a/include/spdlog/spdlog-inl.h b/include/spdlog/spdlog-inl.h
index 97c36222..e02081fe 100644
--- a/include/spdlog/spdlog-inl.h
+++ b/include/spdlog/spdlog-inl.h
@@ -59,6 +59,10 @@ SPDLOG_INLINE void register_logger(std::shared_ptr<logger> logger) {
     details::registry::instance().register_logger(std::move(logger));
 }
 
+SPDLOG_INLINE void register_or_replace(std::shared_ptr<logger> logger) {
+    details::registry::instance().register_or_replace(std::move(logger));
+}
+
 SPDLOG_INLINE void apply_all(const std::function<void(std::shared_ptr<logger>)> &fun) {
     details::registry::instance().apply_all(fun);
 }
diff --git a/include/spdlog/spdlog.h b/include/spdlog/spdlog.h
index 36e7f77d..b51b470b 100644
--- a/include/spdlog/spdlog.h
+++ b/include/spdlog/spdlog.h
@@ -91,8 +91,13 @@ inline void flush_every(std::chrono::duration<Rep, Period> interval) {
 SPDLOG_API void set_error_handler(void (*handler)(const std::string &msg));
 
 // Register the given logger with the given name
+// Will throw if a logger with the same name already exists.
 SPDLOG_API void register_logger(std::shared_ptr<logger> logger);
 
+// Register the given logger with the given name
+// Will replace any the existing logger with the same name if exists.
+SPDLOG_API void register_or_replace(std::shared_ptr<logger> logger);
+
 // Apply a user-defined function on all registered loggers
 // Example:
 // spdlog::apply_all([&](std::shared_ptr<spdlog::logger> l) {l->flush();});
diff --git a/tests/test_registry.cpp b/tests/test_registry.cpp
index 69ec8f53..6397f2a3 100644
--- a/tests/test_registry.cpp
+++ b/tests/test_registry.cpp
@@ -25,6 +25,18 @@ TEST_CASE("explicit register", "[registry]") {
 }
 #endif
 
+TEST_CASE("register_or_replace", "[registry]") {
+    spdlog::drop_all();
+    auto logger1 = std::make_shared<spdlog::logger>(tested_logger_name,
+                                                   std::make_shared<spdlog::sinks::null_sink_st>());
+    spdlog::register_logger(logger1);
+    REQUIRE(spdlog::get(tested_logger_name) == logger1);
+
+    auto logger2 = std::make_shared<spdlog::logger>(tested_logger_name, std::make_shared<spdlog::sinks::null_sink_st>());
+    spdlog::register_or_replace(logger2);
+    REQUIRE(spdlog::get(tested_logger_name) == logger2);
+}
+
 TEST_CASE("apply_all", "[registry]") {
     spdlog::drop_all();
     auto logger = std::make_shared<spdlog::logger>(tested_logger_name,