Gitlab CI/CD - Monorepo

I want to build a monorepo CI/CD based on Gitlab, I think I’m getting stuck at variable expansion inside the if clause. Is there a work around, or could this be a Feature Request for future implementation?

.deploy-serverless-aws:
  stage: deploy
  before_script:
    - cd services/$WORKDIR/
    - sls plugin install -n serverless-python-requirements
    - python3 -m pip install pytest
    - python3 -m pip install -r requirements.txt
    - python3 -m pytest -sq --disable-warnings
  script:
    - serverless deploy --stage $ENV --region ap-southeast-1
  rules:
    - if: '$CI_PIPELINE_SOURCE == "push"'
      changes:
        - services/$WORKDIR/
        - .gitlab-ci.yml
  
deploy-app1:
  extends: .deploy-serverless-aws
  variables:
    WORKDIR: app1

To be clear, I can move the rules to deploy-app1 job and remove the variable and it works, I just think it would be more elegant and avoid duplication if the variable can be expanded before evaluating the changes condition.

This might be nothing, but have you tried quoting the variable values:

deploy-app1:
  extends: .deploy-serverless-aws
  variables:
    WORKDIR: "app1"

Cheers,

Sarah