Nested variables aren't expanded in rules:exists

Summary

!101639 (merged) introduced the ability to use variables in rules:exist, however, nested variables are not expanded. This lack of expansion results in situations where a pipeline/job will not be created.

Reported by customer in Zendesk ticket(internal)

Steps to reproduce

• Create a new project
• Create a folder named deployment
• Create a file named test.yml under the above folder
• Create .gitlab-ci.yml with this content

stages:
    - build

variables:
    TEST_FOLDER: deployment
    TEST_FILE: test
    TEST_PATH: $TEST_FOLDER/$TEST_FILE.yml

test-job1:
    stage: build
    script:
        - echo $TEST_FOLDER
        - echo $TEST_FILE
        - echo $TEST_PATH
    rules:
        - exists:
            - $TEST_FOLDER/$TEST_FILE.yml

test-job2:
    stage: build
    script:
        - echo $TEST_FOLDER
        - echo $TEST_FILE
        - echo $TEST_PATH
    rules:
        - exists:
            - $TEST_PATH

• Validate or run the pipeline
• Observe that the first job is created, however, the second job is not

Proposal

Tentative proposal being discussed below - Add sort_and_expand_all to depends_on

Example Project

https://gitlab.com/gitlab-gold/jiocastillo/ci-testing/variable-expansion

What is the current bug behavior?

Nested variables aren't expanded when used in rules:exist

What is the expected correct behavior?

Nested variables should be expanded when used in rules:exist

Relevant logs and/or screenshots

If the first job is removed, validating or running the pipeline results in:

• Pipeline will not run for the selected trigger. The rules configuration prevented any jobs from being added to the pipeline.