How to use extend with Gitlab CI-Component?

I have this GitLab CI-Component:

spec:
  inputs:
    message:
      default: test
---
.test-component:
  script:
    - echo "$[[ inputs.message ]]"

Also I have this Pipeline:

stages:
  - test

include:
  - component: [my-gitlab-url]/[project-path]/test-component@[commit-sha]
    inputs:
      message: "This is a test job!"

Demo job:
  stage: test
  extends:
    - test-component
  before_script:
    - echo "This is before script!"
  after_script:
    - echo "This is after script!"

The "Demo job" is executed like I wanted (so it works perfectly as a template substitution there). But it also executes the component on its own. But I want to work with components like templates so I can not only outsource jobs but also sub parts of jobs. How can I stop it from executing on its own?

This shows the two jobs (but I only want "Demo job" to be executed):

In your Demo Job you're trying to extend the template test-component but that doesn't exist. You defined the template .test-component, but are trying to include it without the .. Add the . in your job and run it again:

Demo job:
  stage: test
  extends:
    - .test-component
  before_script:
    - echo "This is before script!"
  after_script:
    - echo "This is after script!"