Learn which metadata file defines the main entry point in GitHub custom actions. Understand why action.yml is crucial for configuring inputs, outputs, and runtime settings in your workflows.
Table of Contents
Question
What metadata file in a custom action defines the main entry point?
A. action.js
B. index.js
C. action.yml
D. main.yml
Answer
C. action.yml
Explanation
The correct answer is C. action.yml. The action.yml file (or its alternative, action.yaml) is a required metadata file that defines the main entry point for a custom GitHub Action. This file provides essential configuration details, such as:
- Inputs: Parameters that the action requires to function.
- Outputs: Data that the action produces for subsequent steps.
- Runs Configuration: Specifies how the action should execute, including the runtime environment (e.g., Docker or Node.js) and the entry point script (e.g., index.js).
Why action.yml?
Mandatory for All Actions: GitHub mandates that every custom action must include an action.yml or action.yaml file in its root directory to define its behavior and structure.
Entry Point Definition: The runs section within this file specifies the primary script or executable that serves as the action’s entry point. For example:
runs: using: "node12" main: "index.js"
Here, index.js is defined as the main script to execute.
Standardized YAML Syntax: The YAML format ensures compatibility and readability across different workflows and repositories.
Other Options Explained
A. action.js: This is not a valid metadata file. JavaScript files like index.js are often used as entry point scripts but must be referenced in the action.yml file.
B. index.js: While this can be an entry point script for JavaScript-based actions, it must be declared within the action.yml file under the main key.
D. main.yml: This is not a recognized metadata file for defining custom actions. Workflow files in .github/workflows/ may use .yml, but they are unrelated to defining custom actions.
By correctly configuring the action.yml file, you ensure your custom GitHub Action integrates seamlessly into workflows, making it reusable and efficient across projects.
The action.yml file is the metadata file in a custom GitHub Action that defines the main entry point, including information such as the inputs, outputs, description, and the runs key that specifies the main entry point (e.g., a script or a Docker container).
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