Merge topic 'fetchcontent-set-CMAKE_VERIFY_INTERFACE_HEADER_SETS' into release-3.24

2a9cc3e8e8 FetchContent: Disable header set verification for dependencies

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !7535

Modules/FetchContent.cmake

@@ -364,6 +364,18 @@ Commands
     FetchContent_Declare(other ...)
     FetchContent_MakeAvailable(uses_other other)
 
+  Note that :variable:`CMAKE_VERIFY_INTERFACE_HEADER_SETS` is explicitly set
+  to false upon entry to ``FetchContent_MakeAvailable()``, and is restored to
+  its original value before the command returns.  Developers typically only
+  want to verify header sets from the main project, not those from any
+  dependencies.  This local manipulation of the
+  :variable:`CMAKE_VERIFY_INTERFACE_HEADER_SETS` variable provides that
+  intuitive behavior.  You can use variables like
+  :variable:`CMAKE_PROJECT_INCLUDE` or
+  :variable:`CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE` to turn verification back
+  on for all or some dependencies.  You can also set the
+  :prop_tgt:`VERIFY_INTERFACE_HEADER_SETS` property of individual targets.
+
 .. command:: FetchContent_Populate
 
   .. note::
@@ -1814,6 +1826,13 @@ endfunction()
 # calls will be available to the caller.
 macro(FetchContent_MakeAvailable)
 
+  # We must append an item, even if the variable is unset, so prefix its value.
+  # We will strip that prefix when we pop the value at the end of the macro.
+  list(APPEND __cmake_fcCurrentVarsStack
+    "__fcprefix__${CMAKE_VERIFY_INTERFACE_HEADER_SETS}"
+  )
+  set(CMAKE_VERIFY_INTERFACE_HEADER_SETS FALSE)
+
   get_property(__cmake_providerCommand GLOBAL PROPERTY
     __FETCHCONTENT_MAKEAVAILABLE_SERIAL_PROVIDER
   )
@@ -1965,10 +1984,18 @@ macro(FetchContent_MakeAvailable)
     endif()
   endforeach()
 
+  # Prefix will be "__fcprefix__"
+  list(POP_BACK __cmake_fcCurrentVarsStack __cmake_original_verify_setting)
+  string(SUBSTRING "${__cmake_original_verify_setting}"
+    12 -1 __cmake_original_verify_setting
+  )
+  set(CMAKE_VERIFY_INTERFACE_HEADER_SETS ${__cmake_original_verify_setting})
+
   # clear local variables to prevent leaking into the caller's scope
   unset(__cmake_contentName)
   unset(__cmake_contentNameLower)
   unset(__cmake_contentNameUpper)
   unset(__cmake_providerCommand)
+  unset(__cmake_original_verify_setting)
 
 endmacro()