## Description Allow variables defined global or on job level to have a default value as for example: Using the `${MY_VAR:-default_value}` pattern (Inspired by https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html) This would allow people to fork a project and enable their own `CI_REGISTRY` and propose new Docker images and/or a new `Dockerfile`. But for people which do not enable their registry, using `$CI_REGISTRY_IMAGE` will be an empty string, so in merge requests the build will always fail. ## Bash examples ```bash echo ${VAR1:-default} # => default echo ${VAR1:-$VAR2} # => export VAR2=hello echo ${VAR1:-$VAR2} # => hello export VAR1=thisisvar1 echo ${VAR1:-$VAR2} # => thisisvar1 ``` ## Proposal Example `.gitlab-ci.yml`: ```yaml build: image: ${CI_REGISTRY_IMAGE:-registry.gitlab.com/daniel.widerin/testproject}:build script: - echo "run fancy stuff..." ``` ### Implementation | Work Type | Description | Issue link | | ------ | ------ | ------ | | ~backend | Allow setting a default value for a variable in the `include:ref` field | https://gitlab.com/gitlab-org/gitlab/-/issues/351094 | | ~backend | Allow setting a default value for a variable in the `cache_key:` field | https://gitlab.com/gitlab-org/gitlab/-/issues/351093 | | ~backend | Allow setting a default value for variables in variables: field | https://gitlab.com/gitlab-org/gitlab/-/issues/351092 | | ~backend | Allow default value for variables in `image:` field | https://gitlab.com/gitlab-org/gitlab/-/issues/351091 |