Fix <package>_SOURCE_DIR and _BINARY_DIR handling when caching is active (#314)

* fix: use CACHE variables instead relying on FetchContents mechanism

* apply cmake-format

Signed-off-by: DNKpp <DNKpp2011@gmail.com>

README.md

@@ -274,15 +274,10 @@ See the [wiki](https://github.com/cpm-cmake/CPM.cmake/wiki/More-Snippets) for mo
 CPMAddPackage("gh:catchorg/Catch2@2.5.0")
 ```
 
-### [Boost ](https://github.com/boostorg/boost)
+### [Range-v3](https://github.com/ericniebler/range-v3)
 
-```CMake
-CPMAddPackage(
-  NAME Boost
-  VERSION 1.77.0
-  GITHUB_REPOSITORY "boostorg/boost"
-  GIT_TAG "boost-1.77.0"
-)
+```Cmake
+CPMAddPackage("gh:ericniebler/range-v3#0.11.0")
 ```
 
 ### [Yaml-cpp](https://github.com/jbeder/yaml-cpp)
@@ -292,12 +287,6 @@ CPMAddPackage(
 CPMAddPackage("gh:jbeder/yaml-cpp#yaml-cpp-0.6.3@0.6.3")
 ```
 
-### [Range-v3](https://github.com/ericniebler/range-v3)
-
-```Cmake
-CPMAddPackage("gh:ericniebler/range-v3#0.11.0")
-```
-
 ### [nlohmann/json](https://github.com/nlohmann/json)
 
 ```cmake
@@ -309,6 +298,19 @@ CPMAddPackage(
 )
 ```
 
+### [Boost ](https://github.com/boostorg/boost)
+
+```CMake
+# boost is a huge project and will take a while to download
+# using `CPM_SOURCE_CACHE` is strongly recommended
+CPMAddPackage(
+  NAME Boost
+  VERSION 1.77.0
+  GITHUB_REPOSITORY "boostorg/boost"
+  GIT_TAG "boost-1.77.0"
+)
+```
+
 ### [cxxopts](https://github.com/jarro2783/cxxopts)
 
 ```cmake

cmake/CPM.cmake

@@ -548,6 +548,7 @@ function(CPMAddPackage)
       EXCLUDE_FROM_ALL "${CPM_ARGS_EXCLUDE_FROM_ALL}"
       OPTIONS "${CPM_ARGS_OPTIONS}"
       SOURCE_SUBDIR "${CPM_ARGS_SOURCE_SUBDIR}"
+      DOWNLOAD_ONLY "${DOWNLOAD_ONLY}"
       FORCE True
     )
     cpm_export_variables(${CPM_ARGS_NAME})
@@ -618,10 +619,11 @@ function(CPMAddPackage)
     get_filename_component(download_directory ${download_directory} ABSOLUTE)
     list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS SOURCE_DIR ${download_directory})
     if(EXISTS ${download_directory})
-      # avoid FetchContent modules to improve performance
-      set(${CPM_ARGS_NAME}_BINARY_DIR ${CPM_FETCHCONTENT_BASE_DIR}/${lower_case_name}-build)
-      set(${CPM_ARGS_NAME}_ADDED YES)
-      set(${CPM_ARGS_NAME}_SOURCE_DIR ${download_directory})
+      cpm_store_fetch_properties(
+        ${CPM_ARGS_NAME} "${download_directory}"
+        "${CPM_FETCHCONTENT_BASE_DIR}/${lower_case_name}-build"
+      )
+      cpm_get_fetch_properties("${CPM_ARGS_NAME}")
 
       if(DEFINED CPM_ARGS_GIT_TAG)
         # warn if cache has been changed since checkout
@@ -654,7 +656,7 @@ function(CPMAddPackage)
     endif()
   endif()
 
-  cpm_create_module_file(${CPM_ARGS_NAME} "CPMAddPackage(${ARGN})")
+  cpm_create_module_file(${CPM_ARGS_NAME} "CPMAddPackage(\"${ARGN}\")")
 
   if(CPM_PACKAGE_LOCK_ENABLED)
     if((CPM_ARGS_VERSION AND NOT CPM_ARGS_SOURCE_DIR) OR CPM_INCLUDE_ALL_IN_PACKAGE_LOCK)
@@ -792,18 +794,32 @@ function(cpm_get_fetch_properties PACKAGE)
   if(${CPM_DRY_RUN})
     return()
   endif()
-  FetchContent_GetProperties(${PACKAGE})
-  string(TOLOWER ${PACKAGE} lpackage)
+
   set(${PACKAGE}_SOURCE_DIR
-      "${${lpackage}_SOURCE_DIR}"
+      "${CPM_PACKAGE_${PACKAGE}_SOURCE_DIR}"
       PARENT_SCOPE
   )
   set(${PACKAGE}_BINARY_DIR
-      "${${lpackage}_BINARY_DIR}"
+      "${CPM_PACKAGE_${PACKAGE}_BINARY_DIR}"
       PARENT_SCOPE
   )
 endfunction()
 
+function(cpm_store_fetch_properties PACKAGE source_dir binary_dir)
+  if(${CPM_DRY_RUN})
+    return()
+  endif()
+
+  set(CPM_PACKAGE_${PACKAGE}_SOURCE_DIR
+      "${source_dir}"
+      CACHE INTERNAL ""
+  )
+  set(CPM_PACKAGE_${PACKAGE}_BINARY_DIR
+      "${binary_dir}"
+      CACHE INTERNAL ""
+  )
+endfunction()
+
 # adds a package as a subdirectory if viable, according to provided options
 function(
   cpm_add_subdirectory
@@ -861,6 +877,10 @@ function(cpm_fetch_package PACKAGE populated)
     )
   endif()
 
+  cpm_store_fetch_properties(
+    ${CPM_ARGS_NAME} ${${lower_case_name}_SOURCE_DIR} ${${lower_case_name}_BINARY_DIR}
+  )
+
   set(${PACKAGE}_SOURCE_DIR
       ${${lower_case_name}_SOURCE_DIR}
       PARENT_SCOPE