cmake-gui: empty generator or toolset fails on the reconfigure while set inside the toolchain file

Usage
1

Description

I need to load default valued inside the main CMakeLists.txt script.

If you keep generator & toolset values from CMake GUI empty, they really pass empty values.

The problem is a migration from this issue

Environment

CMake GUI 3.29.0
Windows 10 Pro
Visual Studio 17 2022 generator

Error text from GUI log

  • Nothing was specified in generator & toolset
CMake Error: Error: generator platform: 
Does not match the platform used previously: x64
Either remove the CMakeCache.txt file and CMakeFiles directory or choose a different binary directory.
  • generator was set as x64
CMake Error: Error: generator toolset: 
Does not match the toolset used previously: v143
Either remove the CMakeCache.txt file and CMakeFiles directory or choose a different binary directory.
  • both generator & toolset specified
Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.19045.
Configuring done (0.0s)

Steps to reproduce

  1. Create empty folder with CMakeLists.txt file:
cmake_minimum_required(VERSION 3.24)

set(CMAKE_TOOLCHAIN_FILE "${CMAKE_CURRENT_LIST_DIR}/toolchain.cmake")

project(Test)

And toolchain.cmake file with contents:

if(NOT CMAKE_GENERATOR_TOOLSET)
    set(CMAKE_GENERATOR_TOOLSET "v143" CACHE INTERNAL "Visual Studio toolset to use for CMake")
endif()
if(NOT CMAKE_GENERATOR_PLATFORM)
    set(CMAKE_GENERATOR_PLATFORM "x64" CACHE INTERNAL "Visual Studio platform to use for CMake")
endif()

if(NOT CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE)
    set(CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE "x64" CACHE INTERNAL "Host architecture to use for CMake")
endif()

  1. Load project from CMake GUI

  2. Delete cache through File → Delete Cache

  3. Press Configure button

  4. Use this settings (or another from log):
    image

  5. Press Finish

  6. Wait for configure is finished

  7. Press Configure button again

  8. See the error

2

I’ve removed the CACHE INTERNAL "..." from all variables inside toolchain.cmake and all works as I want