Conditional variables in gitlab-ci.yml - variables

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"

Answer 2

Unfortunatelly YAML-anchors or GitLab-CI's extends don't seem to allow to combine things in script array of commands as of today.
I use built-in variable CI_COMMIT_REF_NAME in combination with global or job-only before_script to solve similar tasks without repeating myself.
Here is an example of my workaround on how to set environment variable to different values dynamically for PROD and DEV during delivery or deployment:
.provide ssh private deploy key: &provide_ssh_private_deploy_key
before_script:
- mkdir -p ~/.ssh
- chmod 700 ~/.ssh
- echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config
- |
if [ "$CI_COMMIT_REF_NAME" == "master" ]; then
echo "$SSH_PRIVATE_DEPLOY_KEY_PROD" > ~/.ssh/id_rsa
MY_DYNAMIC_VAR="we are in master (PROD)"
else
echo "$SSH_PRIVATE_DEPLOY_KEY_DEV" > ~/.ssh/id_rsa
MY_DYNAMIC_VAR="we are NOT in master (DEV)"
fi
- chmod 600 ~/.ssh/id_rsa
deliver-via-ssh:
stage: deliver
<<: *provide_ssh_private_deploy_key
script:
- echo Stage is deliver
- echo $MY_DYNAMIC_VAR
- ssh ...
Also consider this workaround for concatenation of "script" commands: https://stackoverflow.com/a/57209078/470108
hopefully it helps.

Answer 3

A nice way to prepare variables for other jobs is the dotenv report artifact. Unfortunately, these variables cannot be used in many places, but if you only need to access them from other jobs scripts, this is the way:
# prepare environment variables for other jobs
env:
stage: .pre
script:
# Set application version from GIT tag or fake it
- echo "APPVERSION=${CI_COMMIT_TAG:-0.1-dev-$CI_COMMIT_REF_SLUG}+$CI_COMMIT_SHORT_SHA" | tee -a .env
artifacts:
reports:
dotenv: .env
In the script of this job you can conditionally prepare and write your environment values into a file, then make a dotenv artifact out of it. Subsequent - or better yet dependent - jobs will pick up the variables for their scripts from there.