Insufficient dependency definitions in cmake config

For the dependency definitions in CMakeLists.txt, required dependencies are defined in two different ways:

• by using find_package(XCB 1.10 REQUIRED COMPONENTS ..., CMake would fail at this line if dependency not found
• by using

  find_package(KDecoration2 ${PROJECT_VERSION} CONFIG)
  set_package_properties(KDecoration2 PROPERTIES
      TYPE REQUIRED
      PURPOSE "Required for server side decoration support"
  )

  Then with a feature_summary(WHAT ALL INCLUDE_QUIET_PACKAGES FATAL_ON_MISSING_REQUIRED_PACKAGES) at the end.

The second method is fine if there is no other CMake code before that line depending on those required dependencies. In this Kdecoration2 example, at https://invent.kde.org/plasma/kwin/-/blob/master/src/plugins/kdecorations/aurorae/src/config/CMakeLists.txt?ref_type=heads#L1 the variable ${KDECORATION_KCM_PLUGIN_DIR} is required but it's only defined by CMake code within KDecoration2. Since missing KDecoration2 will not cause FATAL_ON_MISSING_REQUIRED_PACKAGES until the feature summary stage, if KDecoration2 is not available we are seeing error:

Must specify INSTALL_NAMESPACE for kcm_auroraedecoration

Without mentioning the actual error is missing KDecoration2 dependency.

To solve these kind of issues, we can either move all required dependency definitions to the first method, or move all the add_package and feature_summary calls before any add_subdirectory call, since CMake files in a subdirectory may have CMake config time dependency on a specific required dependency.