1PROJECT_IS_TOP_LEVEL
2--------------------
3
4.. versionadded:: 3.21
5
6A boolean variable indicating whether the most recently called
7:command:`project` command in the current scope or above was in the top
8level ``CMakeLists.txt`` file.
9
10Some modules should only be included as part of the top level
11``CMakeLists.txt`` file to not cause unintended side effects in the build
12tree, and this variable can be used to conditionally execute such code. For
13example, consider the :module:`CTest` module, which creates targets and
14options:
15
16.. code-block:: cmake
17
18  project(MyProject)
19  ...
20  if(PROJECT_IS_TOP_LEVEL)
21    include(CTest)
22  endif()
23
24The variable value will be true in:
25
26* the top-level directory of the project
27* the top-level directory of an external project added by :module:`ExternalProject`
28
29The variable value will be false in:
30
31* a directory added by :command:`add_subdirectory`
32* a directory added by :module:`FetchContent`
33