Difficulty configuring CI_REGISTRY setting

[dandn]

I'm running renovate using whitesource/renovate-on-prem v2.5.1.

I'm having an issue configuring CI_REGISTRY following the documentation here.

For a given GitLab repo I attempted to add a registryAliases entry by updating the renovate.json file as follows:

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "dependencyDashboard": true,
  "registryAliases": {
    "$CI_REGISTRY": "docker-registry.mycompany.net"
  }
}

This approach does not work as I get the following Action Required: Fix Renovate Configuration generated under GitLab issues:

Location: renovate.json
Error type: The renovate configuration file contains some invalid settings
Message: Invalid 'registryAliases.registryAliases.$CI_REGISTRY' configuration: value is not a url

Presumably I am not adding this registryAliases entry correctly.
Could anyone advise how to correct the entry within renovate.json ?
(Or does this setting rather have to go in config.js)?

[rarkins]

It's expecting the URL to be in format https://...... That validation might be too strict.

You can try in config.js because Renovate doesn't perform strict validation there, but of course it looks like something needs fixing.

[dandn]

Yes indeed. In my example above, using https://docker-registry.mycompany.net will not generate the renovate error.
However, prepending the https results in incorrectly formatted docker images.

I will attempt to move this to the config.js and report back.
In the meantime, should I escalate this to an issue? (At the very least something to be clarified in the documentation?)

[rarkins]

Yes, please create an issue. At the minimum we have a docs problem, but perhaps we need to loosen the registryAliases validation