### Summary When triggering a downstream pipeline from a bridge job in `.gitlab-ci.yml`, using the `trigger` keyword, it is not possible to use a variable for the project name. Although this may be considered not a bug, but just a limitation, if a bridge job is configured like this, it will hang forever. No error message is displayed and the pipeline needs to be cancelled manually. This was first discussed as part of #202239, but apparently is a separate issue. ### Steps to reproduce In `.gitlab-ci.yml`, create a pipeline trigger bridge job in which the downstream project name is stored within a variable: ```yaml some_test: stage: test script: - echo "If this were real, tests would run at this point." some_integration_test: stage: integration variables: INTEGRATION_PROJECT: my/downstream-project trigger: project: $INTEGRATION_PROJECT ``` - The limitation that variable expansion is not supported for the project property is not made explicit in the [documentation](https://docs.gitlab.com/ee/ci/multi_project_pipelines.html#triggering-a-downstream-pipeline-using-a-bridge-job). It says that variable expansion is supported. This is written right after explaining the `branch` property, but the wording does not make clear that it is limited to that property. (FWIW, I checked if I can use variables for `branch` and this works.) ### What is the expected *correct* behavior? Different variants are possible (sorted from most effort/best UX to minimal effort/worst UX): 1. Ideally, variable expansion would be support for the `project` property. 3. At the very least, the documentation should make perfectly clear that variable expansion is not supported here.