[build2] Custom Configuration Variables for the Config Module

[Markus Pawellek]

Markus Pawellek <markus.pawellek at mailbox.org> wrote:

> currently and as an exercise, I am porting the build system
> of the GLFW library from CMake to build2 for Linux platforms.
> Due to simplicity, I have only done this for X11 platforms
> without the possibility of linking to the Vulkan library.
> But I would like to add support for Vulkan and Wayland as
> described in the official CMake files by the GLFW repository.
> Both of these alternatives should be choose-able from the
> outside via the config module of build2.
> 
> For this, I wanted to provide custom configuration variables,
> like 'config.graphics.protocol = wayland / x11' and
> 'config.graphics.api = opengl / vulkan'.
> Using only the syntax of the buildfile and the functionality
> of build2 itself without the config module,
> I was able to do this by always providing the respective
> variables as command-line argument to 'b' as described in the
> documentation for non-persistent builds.
> Using the config module, manually adding custom variables to
> the 'config.build' file of my project was working.
> But the moment I changed the configuration with the command-line
> tools, all custom variables vanished.
> 
> Is there already a better workaround to provide such custom variables?
> Otherwise, would it be possible to provide this functionality?
> In this case, maybe it would even be useful to have the same mechanism
> for custom configuration variables as for the already given variable pairs,
> such as 'config.cxx.poptions' and 'cxx.poptions'.
> Thank you in advance.

Right now, I am little bit embarassed.
Until now, I have not read the NEWS file or the currently existing issues on GitHub.
My questions are already answered and a solution seems to be already implemented.
So I am very sorry that I have bothered you with this message.
Please forget it.