[skip ci] Handle OPTIONAL_COMPONENTS in find_package(YARP)

There is no way to make this work with `find_dependency()` since it
passes caller's REQUIRED to the underlying `find_package()` call.
That is, no error should be raised if an optional component was not
found while issuing a `find_package(YARP REQUIRED ...)` command.

cmake/template/YARPConfig.cmake.in

@@ -7,7 +7,6 @@
 
 
 
-include(CMakeFindDependencyMacro)
 include(CMakeDependentOption)
 
 
@@ -144,27 +143,23 @@ endif()
 # Find all requested components
 set(YARP_LIBRARIES YARP::YARP_init)
 foreach(_yarp_module ${YARP_FIND_COMPONENTS})
-  # FIXME Remove this check when CMake 3.9 or later is required
-  if (CMAKE_VERSION VERSION_LESS 3.9)
-    set(_YARP_FIND_PARTS_REQUIRED)
-    if (YARP_FIND_REQUIRED)
-      set(_YARP_FIND_PARTS_REQUIRED REQUIRED)
-    endif()
-    set(_YARP_FIND_PARTS_QUIET)
-    if (YARP_FIND_QUIETLY)
-      set(_YARP_FIND_PARTS_QUIET QUIET)
-    endif()
-    find_package(YARP_${_yarp_module}
-                 ${_YARP_FIND_PARTS_QUIET}
-                 ${_YARP_FIND_PARTS_REQUIRED}
-                 HINTS "${YARP_CMAKECONFIG_DIR}"
-                 NO_DEFAULT_PATH)
-  else()
-    find_dependency(YARP_${_yarp_module}
-                    HINTS "${YARP_CMAKECONFIG_DIR}"
-                    NO_DEFAULT_PATH)
+  set(_YARP_FIND_PART_${_yarp_module}_REQUIRED)
+  # Only propagate REQUIRED if module was not passed to OPTIONAL_COMPONENTS
+  if(YARP_FIND_PARTS_REQUIRED AND YARP_FIND_REQUIRED_${_yarp_module})
+    set(_YARP_FIND_PART_${_yarp_module}_REQUIRED REQUIRED)
+  endif()
+  set(_YARP_FIND_PARTS_QUIET)
+  if(YARP_FIND_QUIETLY)
+    set(_YARP_FIND_PARTS_QUIET QUIET)
+  endif()
+  find_package(YARP_${_yarp_module}
+               ${_YARP_FIND_PARTS_QUIET}
+               ${_YARP_FIND_PART_${_yarp_module}_REQUIRED}
+               HINTS "${YARP_CMAKECONFIG_DIR}"
+               NO_DEFAULT_PATH)
+  if(YARP_${_yarp_module}_FOUND)
+    list(APPEND YARP_LIBRARIES YARP::YARP_${_yarp_module})
   endif()
-  list(APPEND YARP_LIBRARIES YARP::YARP_${_yarp_module})
 endforeach()
 
 # Restore the original value of the variable

doc/release/v3_0_1.md

@@ -25,6 +25,7 @@ Bug Fixes
   be used instead).
 * Deprecation warnings when calling find_package(YARP) more than once are no
   longer printed.
+* Added missing support for `OPTIONAL_COMPONENTS` in `find_package(YARP)` calls.
 
 
 ### Libraries