cas 3 compatibility

It is IMHO a better practice to specify the required version in the info.yml file instead of composer.json.
This way it is used both by Drupal to validate the constraint when enabling the module and by drupal.org when generating the Composer package.

prudloff → changed the visibility of the branch 3494490-cas-3-compatibility to hidden.

prudloff → changed the visibility of the branch 3494490-cas-3-compatibility to active.

Until this is resolved, you could add the following to your composer's repositories property, just above the https://packages.drupal.org/8 repository:

{
    "type": "package",
    "package": {
    "name": "drupal/cas_attributes",
        "description": "Provides tokens for CAS attributes and an interface for token replacement in user account fields as well as advanced role mapping capability.",
        "type": "drupal-module",
        "keywords": ["Drupal", "CAS", "single sign-on"],
        "homepage": "https://www.drupal.org/project/cas_attributes",
        "support": {
            "issues": "https://www.drupal.org/project/issues/cas_attributes",
            "source": "https://git.drupalcode.org/project/cas_attributes"
        },
        "license": "GPL-2.0+",
        "require": {
            "drupal/cas": "^2.1 || ^3.0"
        },
        "version": "2.0.0-beta5",
        "source": {
            "url": "https://git.drupalcode.org/project/cas_attributes.git",
            "type": "git",
            "reference": "2.0.0-beta5"
        }
    }
},

Depending on the version you currently use, you might need to delete your "vendor" folder.

@prudloff I'm not completely sure at this time whether the "Works with" in the "Releases" tab uses the composer.json or the info.yml.
I think in most cases the dependencies are described in both composer.json and .info.yml. Specific version requirements are usually set in composer.json only; though there are some cases where it's used in info.yml too but I would call them rather rare (see example).

Whatever the maintainers decide though...