How to set variable inline in gitlab-ci.yaml based on regex matching? - regex

Question

I am trying to create a variable in gitlab-ci.yaml based on the name of the branch.
Suppose I am pushing to a branch named 3.2.7
Here is the situation:
include:
- template: "Workflows/Branch-Pipelines.gitlab-ci.yml"
variables:
PRODUCTION_BRANCH: "master"
STAGING_BRANCH: (\d)\.(\d)\.(\d)
.deploy_rules:
rules:
- if: '$CI_COMMIT_BRANCH =~ /$STAGING_BRANCH/'
variables:
SERVER_PORT: 3007 # TODO: should be 300d ; d is the second digit
I want to generate 3002 inline using regex matching.
How can I do this?
I have done some research and seems I have to use sed but I am not sure if it is the best way to do it and how to do it.
TO MAKE THE PROBLEM SIMPLER
include:
- template: "Workflows/Branch-Pipelines.gitlab-ci.yml"
variables:
TEST_VAR: sed -E 's/(\d)\.(\d)\.(\d)/300\2/gm;t;d' <<< $CI_COMMIT_BRANCH
stages:
- temp
temp:
stage: temp
script:
- echo $TEST_VAR
Should be echoing 3002 but it is echoing sed -E 's/(\d)\.(\d)\.(\d)/300\2/gm;t;d' <<< 3.2.7

Answer 1

You can't use variables in the regex pattern. You just have to write the regex verbatim, it cannot be directly parameterized. You also cannot use sed or other Linux utilities in variables: or other parts of your yaml. You're bound to the limitations of YAML specification and features provided by GitLab.
However, there is an option available to you that will fit your stated use case.
Dynamic variables
TEST_VAR: sed -E 's/(\d).(\d).(\d)/300\2/gm;t;d' <<< $CI_COMMIT_BRANCH
While you can't use sed or other utilities directly in variables: declarations, you can use dotenv artifacts via artifacts:reports:dotenv to set variables dynamically.
For example, a job can use sed or whatever other utilities you like to create variables which will be used by the rest of the pipeline.
stages:
- temp
create_variables:
stage: .pre
script:
- TEST_VAR="$(sed -E 's/(\d)\.(\d)\.(\d)/300\2/gm;t;d' <<< ${CI_COMMIT_BRANCH})"
- echo "TEST_VAR=${TEST_VAR}" >> dotenv.txt
artifacts:
reports:
dotenv: dotenv.txt
temp:
stage: temp
script:
- echo $TEST_VAR
Here, the .pre stage is used, which is a special stage that is always ordered before every other stage. The dotenv artifact from the create_variables job will dynamically create variables for the jobs in subsequent stages that receive the artifact.