Simplified local-package with TODO for allowing as extension-point

cmake/CPM.cmake

@@ -611,18 +611,16 @@ function(CPMAddPackage)
     return()
   endif()
 
-  # Check for ENV overide for local package-source when not already defined. NOTE: Uses a recursive
-  # CPMAddPackage call where `CPM_${CPM_ARGS_NAME}_SOURCE` == "" which causes first if-case to stop
-  # recusrion
-  if(CPM_${CPM_ARGS_NAME}_SOURCE)
-    file(TO_CMAKE_PATH "${CPM_${CPM_ARGS_NAME}_SOURCE}" PACKAGE_SOURCE)
-  elseif(DEFINED ENV{CPM_${CPM_ARGS_NAME}_SOURCE})
-    file(TO_CMAKE_PATH "$ENV{CPM_${CPM_ARGS_NAME}_SOURCE}" PACKAGE_SOURCE)
+  # @TODO Allow this as from a user-extension point for locating package source e.g. Check for ENV
+  # overide for local package-source
+  if(NOT DEFINED CPM_${CPM_ARGS_NAME}_SOURCE AND DEFINED ENV{CPM_${CPM_ARGS_NAME}_SOURCE})
+    file(TO_CMAKE_PATH $ENV{CPM_${CPM_ARGS_NAME}_SOURCE} CPM_${CPM_ARGS_NAME}_SOURCE)
   endif()
 
   # Check for manual overrides
-  if(NOT CPM_ARGS_FORCE AND NOT "${PACKAGE_SOURCE}" STREQUAL "")
-    set(CPM_${CPM_ARGS_NAME}_SOURCE "") # Assign empty to prevent recursion
+  if(NOT CPM_ARGS_FORCE AND NOT "${CPM_${CPM_ARGS_NAME}_SOURCE}" STREQUAL "")
+    set(PACKAGE_SOURCE ${CPM_${CPM_ARGS_NAME}_SOURCE})
+    set(CPM_${CPM_ARGS_NAME}_SOURCE "")
     CPMAddPackage(
       NAME "${CPM_ARGS_NAME}"
       SOURCE_DIR "${PACKAGE_SOURCE}"