find_package: allow to specify value of cmake variables

I think it would be nice to be able to pass requested cmake variables to find_package. That is, doing something like

find_package (MyLib REQUIRED REQUIRED_VARIABLES option1 ON option2 OFF var1 "a;b;c" var2 "foo")

If an installation is found with option1=OFF or option2=ON or var1/var2 different from the specified values, it should be rejected.

Some context: I tried to do something like

find_package (MyLib QUIET)
if (MyLib_FOUND)
  # Check if certain vars have a value that is compatible with my needs.
  # If not, set MyLIB_FOUND=FALSE, to trigger code below
endif()

if (NOT MyLib_FOUND)
  # Use FetchContent to build locally
endif()

The problem with this is that find_package creates imported targets for MyLib as soon as it finds it, so when FetchContent would try to add the subdirectory, I would get errors because of a redefined target.

My workaround was to use ExternalProject, but I don't like that it runs at build time (forcing me to choose between hard-coding MyLib targets specs or running a separate cmake project on the fly at config time, to config/build/install MyLib). I really want to stick with FetchContent.

Note: I tried to pass OVERRIDE_FIND_PACKAGE to FetchContent_Declare, hoping that it would allow to "throw away" the imported targets, but that's not what it was designed for (and in fact, it doesn't work, b/c declared targets can never be "discarded").

Note: while it's true that "if you need a different install, set MyLib_ROOT to point to the specific installation you need", I've seen people (which may or may not be me) accidentally update an installation of a package on a production machine, because they copy/pasted a config script without changing the installation folder. Finding out why some test failed was complicated, until I added the checks on the tpl vars right after the successful find_package call.

I looked at find_package documentation, and I don't think this is currently possible. I was wondering if this feature could be of general interest, or if it's too specific and/or too complicated to add.