Module 2 Lesson 5: The Pipeline Editor and Linter

There is nothing more frustrating than waiting 5 minutes for a build to start, only to see it fail with a "YAML Syntax Error." GitLab provides two tools to prevent this: the Pipeline Editor and the CI Linter.

1. The Pipeline Editor

Found under Build -> Pipeline Editor in the GitLab sidebar.

• Live Validation: As you type, it tells you if your YAML is valid or broken.
• Visualization: It shows a graphical map of your Stages and Jobs.
• Template Browser: It allows you to see the source code of any "Included" templates (like GitLab's official security templates).

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2. The CI Linter

This is a more "Rigid" tool used to validate a file you've already written.

• Input: Paste your whole .gitlab-ci.yml.
• Output: It tells you exactly which line is broken and why (e.g., "Job 'test' is missing 'script' keyword").

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3. Visualization: The Graph

The most powerful feature of the editor is the Visualization tab.

• It helps you spot "Bottlenecks." (e.g., "Why is my production job waiting for the documentation job to finish?").
• It shows dependencies between jobs (the "Needs" keyword, which we will learn later).

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4. Best Practice: Lint before Push

1. Write your YAML in VS Code.
2. Paste it into the GitLab CI Linter or use a VS Code extension.
3. Fix the errors.
4. COMMIT and PUSH.

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Exercise: The Linter Debugger

1. Go to your GitLab project -> Build -> Pipeline Editor.
2. Type a job name but forget the script: keyword. What error does the top bar show?
3. Add the script: keyword back. Does the error disappear?
4. Switch to the "Visualize" tab. How many stages do you see?
5. Why is the Pipeline Editor better than just editing the file in the standard "Code" browser?

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Summary

You have completed Module 2: GitLab CI/CD Basics. You now know how to design a pipeline, understand its architecture, and verify its correctness.

Next Module: Time for action: Module 3: Building Your First Pipeline.