How to consume "conda_build_config.yaml" in conda-build format in rattler-build?

[traversaro]

Hello everyone, and thanks for working on rattler-build!

I am looking into migrating to rattler-build two channels that are build downstream to conda-forge, robostack (https://robostack.github.io/) and robotology (https://github.com/robotology/robotology-superbuild/blob/v2024.11.1/doc/conda-recipe-generation.md).

In both cases, one fundamental piece of the infrastructure was making sure that the pinning used in the downstream channel were compatible with the global conda-forge pinnings defined in https://github.com/conda-forge/conda-forge-pinning-feedstock/blob/main/recipe/conda_build_config.yaml (typically with some additional modifications, if we need to override the pinnings) . With conda-build, this just boils down to copy that file (or just install it with the conda-forge-pinning conda-forge package) and pass it to conda-build with the -m option.

However, as far as I know (see also https://discord.com/channels/1082332781146800168/1082338253925003385/1275107319272968283) this is not possible anymore in rattler-build, as the conda_build_config.yaml format used in rattler-build is different from the format of conda_build_config.yaml used in conda-build.

However, I guess there is some logic in the rerendering logic to support rattler-build recipes in conda-forge to convert the conda_build_config.yaml from conda-build format to rattler-build format, so I was wondering if anyone had some suggestions on this, thanks in advance!