cmake/Help/variable/PROJECT-NAME_IS_TOP_LEVEL.rst

<PROJECT-NAME>_IS_TOP_LEVEL
---------------------------

.. versionadded:: 3.21

A boolean variable indicating whether the named project was called in a top
level ``CMakeLists.txt`` file.

To obtain the value from the most recent call to :command:`project` in
the current directory scope or above, see the
:variable:`PROJECT_IS_TOP_LEVEL` variable.

The variable value will be true in:

* the top-level directory of the project
* the top-level directory of an external project added by
  :module:`ExternalProject`
* a directory added by :command:`add_subdirectory` that does not also contain
  a :command:`project` call
* a directory added by :command:`FetchContent_MakeAvailable`,
  if the fetched content does not contain a :command:`project` call

The variable value will be false in:

* a directory added by :command:`add_subdirectory` that also contains
  a :command:`project` call
* a directory added by :command:`FetchContent_MakeAvailable`,
  if the fetched content contains a :command:`project` call