CMAKE_REQUIRE_FIND_PACKAGE_<PackageName>

Added in version 3.22.

Variable for making find_package() call REQUIRED.

Every non-REQUIRED find_package() call in a project can be turned into REQUIRED by setting the variable CMAKE_REQUIRE_FIND_PACKAGE_<PackageName> to TRUE. This can be used to assert assumptions about build environment and to ensure the build will fail early if they do not hold.

Note that setting this variable to true breaks some commonly used patterns. Multiple calls to find_package() are sometimes used to obtain a different search order to the default. For example, projects can force checking a known path for a particular package first before searching any of the other default search paths:

find_package(something PATHS /some/local/path NO_DEFAULT_PATH)
find_package(something)

In the above, the first call looks for the something package in a specific directory. If CMAKE_REQUIRE_FIND_PACKAGE_something is set to true, then this first call must succeed, otherwise a fatal error occurs. The second call never gets a chance to provide a fall-back to using the default search locations.

A similar pattern is used even by some of CMake's own Find modules to search for a config package first:

find_package(something CONFIG QUIET)
if(NOT something_FOUND)
  # Fall back to searching using typical Find module logic...
endif()

Again, if CMAKE_REQUIRE_FIND_PACKAGE_something is true, the first call must succeed. It effectively means a config package must be found for the dependency, and the Find module logic is never used.

See also the CMAKE_DISABLE_FIND_PACKAGE_<PackageName> variable.