Improved variables names to make it more obvious what's going on.

CMakeLists.txt

@@ -26,12 +26,11 @@ add_subdirectory(third_party)
 # available otherwise we fallback to the older protobuf method. TODO: Simplify
 # once we can require cmake 3.27 (where CONFIG is default).
 find_package(Protobuf QUIET CONFIG)
-if(${Protobuf_FOUND})
- set(PROTOBUF_LOADED_AS_CONFIG ON)
-else()
+set(ABSL_INCLUDED_WITH_PROTOBUF ON)
+if(NOT ${Protobuf_FOUND})
  find_package(Protobuf REQUIRED)
  include_directories(${Protobuf_INCLUDE_DIRS})
- set(PROTOBUF_LOADED_AS_CONFIG OFF)
+ set(ABSL_INCLUDED_WITH_PROTOBUF OFF)
 endif()
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake_modules")

third_party/CMakeLists.txt

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 
-if(NOT ${PROTOBUF_LOADED_AS_CONFIG})
+if(NOT ${ABSL_INCLUDED_WITH_PROTOBUF})
  set(ABSL_PROPAGATE_CXX_STD ON)
  add_subdirectory(abseil-cpp)
 endif()