db(mysql): fix Connector/C++ alias linkage and CMake detection

Author: GaspardKirira

CMakeLists.txt

@@ -77,6 +77,12 @@ if (VIX_DB_USE_MYSQL)
   if (TARGET MySQLCppConn::MySQLCppConn)
     set(VIX_DB_HAS_MYSQL ON)
     message(STATUS "[vix_db] mysql: enabled (alias)")
+    get_target_property(_vix_mysql_loc MySQLCppConn::MySQLCppConn IMPORTED_LOCATION)
+    if (NOT _vix_mysql_loc)
+      message(WARNING "[vix_db] mysql: alias target exists but has no IMPORTED_LOCATION. Disabling.")
+      set(VIX_DB_HAS_MYSQL OFF)
+      set(VIX_DB_USE_MYSQL OFF)
+    endif()
   else()
     if (VIX_DB_REQUIRE_MYSQL)
       message(FATAL_ERROR "[vix_db] mysql requested but Connector/C++ not found (VIX_DB_REQUIRE_MYSQL=ON).")
@@ -342,7 +348,20 @@ endif()
 # Link drivers (single source of truth)
 # ------------------------------------------------------------------------------
 if (VIX_DB_HAS_MYSQL)
-  target_link_libraries(vix_db PUBLIC MySQLCppConn::MySQLCppConn)
+  # Flatten the imported target into real link flags so consumers
+  # always link the connector (important for static vix_db).
+  get_target_property(_vix_mysql_lib MySQLCppConn::MySQLCppConn IMPORTED_LOCATION)
+  get_target_property(_vix_mysql_inc MySQLCppConn::MySQLCppConn INTERFACE_INCLUDE_DIRECTORIES)
+
+  if (NOT _vix_mysql_lib)
+    message(FATAL_ERROR "[vix_db] mysql enabled but MySQLCppConn::MySQLCppConn has no IMPORTED_LOCATION")
+  endif()
+
+  target_link_libraries(vix_db PUBLIC "${_vix_mysql_lib}")
+
+  if (_vix_mysql_inc)
+    target_include_directories(vix_db PUBLIC "${_vix_mysql_inc}")
+  endif()
 endif()
 
 if (VIX_DB_HAS_SQLITE)

cmake/MySQLCppConnAlias.cmake

@@ -78,6 +78,22 @@ if (NOT MYSQLCPPCONN_LIB OR NOT MYSQLCPPCONN_INCLUDE_DIR)
   return()
 endif()
 
+# ------------------------------------------------------------------------------
+# Validate that the picked library really provides the symbol we need.
+# Avoid "half-found" connector variants that compile but fail at link time.
+# ------------------------------------------------------------------------------
+if (UNIX AND EXISTS "${MYSQLCPPCONN_LIB}")
+  execute_process(
+    COMMAND bash -c "nm -D \"${MYSQLCPPCONN_LIB}\" 2>/dev/null | grep -q \"get_driver_instance\""
+    RESULT_VARIABLE _vix_mysql_has_symbol
+  )
+  if (NOT _vix_mysql_has_symbol EQUAL 0)
+    message(WARNING "[vix_db] MySQLCppConn fallback: '${MYSQLCPPCONN_LIB}' does not export get_driver_instance(). Disabling MySQL driver.")
+    unset(MYSQLCPPCONN_LIB CACHE)
+    return()
+  endif()
+endif()
+
 # Define imported target
 add_library(MySQLCppConn::MySQLCppConn UNKNOWN IMPORTED)