Provide CMake components for different serialization formats

[deckstose]

CMake supports finding specific package components, this is most prominently known with Qt, where you can call find_package(Qt6 REQUIRED COMPONENTS Widgets) to use widgets, but not the networking code for example.

The wish comes from the fact that I've recently evaluated to use this library and in the process came across the Debian package, which is compiled against all serialization formats. However, even if you just want to use json and toml, find_package will fail to find a good bson version. This is definitely a Debian packaging problem, however the library should provide a way to be packaged with all formats and only compile against the required parts when a user will only use a subset.

Copy-Paste Reproducer

Here a quick copy paste guide to reproduce:

podman run --rm -it --pull always debian:unstable
apt update && apt upgrade -y && apt install -y --no-install-recommends build-essential cmake ninja-build && apt install -y libreflectcpp-dev libtomlplusplus-dev libbson-dev

# CMakeLists.txt
cmake_minimu_required(VERSION 3.30)
project(foo CXX)
find_package(reflectcpp REQUIRED)
add_executable(foo foo.cc)

// foo.cc
auto main() -> int { return 0; }

cmake -B build -G Ninja

[liuzicheng1987]

@deckstose, I have to admit, I am not entirely sure what you want is to do here.

The library itself absolutely provides that. If you only compile the JSON and TOML features than only those dependencies are installed and required.

I wasn't involved in making the Debian package, and frankly, didn't even know that one existed, so I can't really say much about that.