ExternalProject: Replace location tags in CMAKE_CACHE_ARGS

When we added CMAKE_CACHE_ARGS, we did not try it with any
<SOURCE_DIR> or <INSTALL_DIR> references. This commit fixes
that accidental omission.

Modules/ExternalProject.cmake

@@ -550,7 +550,24 @@ function(_ep_set_directories name)
   endforeach()
 endfunction(_ep_set_directories)
 
-function(_ep_write_initial_cache script_filename args)
+
+# IMPORTANT: this MUST be a macro and not a function because of the
+# in-place replacements that occur in each ${var}
+#
+macro(_ep_replace_location_tags target_name)
+  set(vars ${ARGN})
+  foreach(var ${vars})
+    if(${var})
+      foreach(dir SOURCE_DIR BINARY_DIR INSTALL_DIR TMP_DIR)
+        get_property(val TARGET ${target_name} PROPERTY _EP_${dir})
+        string(REPLACE "<${dir}>" "${val}" ${var} "${${var}}")
+      endforeach()
+    endif()
+  endforeach()
+endmacro()
+
+
+function(_ep_write_initial_cache target_name script_filename args)
   # Write out values into an initial cache, that will be passed to CMake with -C
   set(script_initial_cache "")
   set(regex "^([^:]+):([^=]+)=(.*)$")
@@ -584,6 +601,8 @@ function(_ep_write_initial_cache script_filename args)
     set(setArg "${setArg}${accumulator}\" CACHE ${type} \"Initial cache\" FORCE)")
     set(script_initial_cache "${script_initial_cache}\n${setArg}")
   endif()
+  # Replace location tags.
+  _ep_replace_location_tags(${target_name} script_initial_cache)
   # Write out the initial cache file to the location specified.
   if(NOT EXISTS "${script_filename}.in")
     file(WRITE "${script_filename}.in" "\@script_initial_cache\@\n")
@@ -864,14 +883,7 @@ function(ExternalProject_Add_Step name step)
   endif()
 
   # Replace location tags.
-  foreach(var comment command work_dir)
-    if(${var})
-      foreach(dir SOURCE_DIR BINARY_DIR INSTALL_DIR TMP_DIR)
-        get_property(val TARGET ${name} PROPERTY _EP_${dir})
-        string(REPLACE "<${dir}>" "${val}" ${var} "${${var}}")
-      endforeach()
-    endif()
-  endforeach()
+  _ep_replace_location_tags(${name} comment command work_dir)
 
   # Custom comment?
   get_property(comment_set TARGET ${name} PROPERTY _EP_${step}_COMMENT SET)
@@ -1271,7 +1283,7 @@ function(_ep_add_configure_command name)
     get_property(cmake_cache_args TARGET ${name} PROPERTY _EP_CMAKE_CACHE_ARGS)
     if(cmake_cache_args)
       set(_ep_cache_args_script "${tmp_dir}/${name}-cache.cmake")
-      _ep_write_initial_cache("${_ep_cache_args_script}" "${cmake_cache_args}")
+      _ep_write_initial_cache(${name} "${_ep_cache_args_script}" "${cmake_cache_args}")
       list(APPEND cmd "-C${_ep_cache_args_script}")
     endif()
 

Tests/ExternalProject/CMakeLists.txt

@@ -115,7 +115,8 @@ if(can_build_tutorial_step5)
   set(proj TutorialStep5-Local)
   ExternalProject_Add(${proj}
     URL "${CMAKE_CURRENT_SOURCE_DIR}/../Tutorial/Step5"
-    CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -G ${CMAKE_GENERATOR} <SOURCE_DIR>
+    CMAKE_CACHE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
+    CMAKE_ARGS -G ${CMAKE_GENERATOR} <SOURCE_DIR>
     TEST_BEFORE_INSTALL 1
     LOG_INSTALL 1
   )