Missing documentation on the structure of mixins

[allsey87]

I am trying to understand how mixin are structured and have been unable to find any documentation on this. Taking compile-commands.mixin as an example, I understand that build is the verb to which this mixin applies and that cmake-args refers to the CMake build system, but what does compile-commands refer to? Is this the name of a specific package?

{
    "build": {
        "compile-commands": {
            "cmake-args": [
                "-DCMAKE_EXPORT_COMPILE_COMMANDS=ON",
                "--no-warn-unused-cli"
            ]
        }
    }
}

It would be great if a couple notes on this could be added to the README.md or over at readthedocs.

[christophebedard]

compile-commands is the name of the mixin, so you'd use it like --mixin compile-commands.

If you remove the layer with the name of the mixin, the structure is similar to structures for .meta, colcon.pkg, and defaults.yaml files: https://colcon.readthedocs.io/en/released/user/configuration.html. Those also need more explicit documentation about their structure; there were similar comments/requests for this in the past.