Conditional variables in gitlab-ci.yml

Question

Depending on branch the build comes from I need to use slightly different command line arguments. Particularly I would like to upload snapshot nexus artifacts when building from a branch, and release artifact when building off master.

Is there a way to conditionally alter variables?

I tried to use except/only keywords like this

stages:
    - stage


variables:
    TYPE: Release


.upload_common:
    stage: stage
    tags: ["Win"]
    script: 
        - echo Uploading %TYPE%


.upload_snapshot:
    variables:
        TYPE: "Snapshot"
    except:
        - master


upload:
    extends: 
        - .upload_common
        - .upload_snapshot

Unfortunately it skips whole upload step when building off master.

The reason I am using 'extends' pattern here is that I have win and mac platforms which use slightly different variables substitution syntax ($ vs %). I also have a few different build configuration - Debug/Release, 32bit/64bit.

The code below actually works, but I had to duplicate steps for release and snapshot, one is enabled at a time.

stages:
    - stage


.upload_common:
    stage: stage
    tags: ["Win"]
    script: 
        - echo Uploading %TYPE%


.upload_snapshot:
    variables:
        TYPE: "Snapshot"
    except:
        - master

.upload_release:
    variables:
        TYPE: "Release"
    only:
        - master


upload_release:
    extends: 
        - .upload_common
        - .upload_release


upload_snapshot:
    extends: 
        - .upload_common
        - .upload_snapshot

The code gets much larger when snapshot/release configuration is multiplied by Debug/Release, Mac/Win, and 32/64bits. I would like to keep number of configurations at minimum.

Having ability to conditionally altering just a few variables would help me reducing this code a lot.

Answer 1

Another addition in GitLab 13.7 are the rules:variables. This allows some logic in setting vars:

job:
  variables:
    DEPLOY_VARIABLE: "default-deploy"
  rules:
    - if: $CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH
      variables:                              # Override DEPLOY_VARIABLE defined
        DEPLOY_VARIABLE: "deploy-production"  # at the job level.
    - if: $CI_COMMIT_REF_NAME =~ /feature/
      variables:
        IS_A_FEATURE: "true"                  # Define a new variable.
  script:
    - echo "Run script with $DEPLOY_VARIABLE as an argument"
    - echo "Run another script if $IS_A_FEATURE exists"