pages.expire_in does not accept variables

The pages.expire_in setting behaves a little inconsistent. It seems to have this behavior:

if pages.expire_in == nil
  # Default if parallel deployment
  if pages.path_prefix
    return '24 hours'
  else
    # Default if main deployment
    return 'never'
  end
else
  return pages.expire_in
end

The problem which arises from this, is that increasing the expire_in to e.g. one week also sets one week for the main deployment. Unluckily one cannot use a variable to set expire_in. And because one can just have one pages job, either needs to rely on the default behavior, a high expire_in or never. There is seems no way to have parallel deployments expire within time frame X while setting the main deployment to never.

See also:

which was caused by: gitlab-org/gitlab-services/design.gitlab.com@99d85951

Workaround:

As Pages now supports User-defined job names, users can define multiple Pages jobs and set different expire_in values for different rules.

Example:

main-pages:
  stage: deploy
  script:
    - ...
  pages:  # specifies that this is a Pages job and publishes the default public directory
    expire_in: never
  rules:
    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH

mr-pages:
  stage: deploy
  script:
    - ...
  pages:  # specifies that this is a Pages job and publishes the default public directory
    expire_in: 1 week
  rules:
    - if: $CI_PIPELINE_SOURCE == "merge_request_event"