Hello action

[github-learning-lab]

Anatomy of an action

Earlier you learned how the different pieces of the GitHub Actions feature work together. Now you will learn about the components that make up an individual action.

Remember, and action is the unit of work that a workflow file executes when it reaches that task. They are called by referencing them as the value to the uses: key in a workflow step.

What makes up an action?

JavaScript actions are consist of two key components:

Component	Description
JavaScript source code files	These files contain the logic of your action. This includes any dependencies or custom modules that your main logic may need.
Action metadata file	This file contains information that the actions source code can use. An example of this is allowing a developer to specify an API key as an input variable for your action to consume. This file MUST be named action.yml

Let's take a look at how those components fit in with the workflow file.

Although the workflow file is used to allow us to set the inputs and outputs using the with: keyword it is not a required component of an individual action.

The failing workflow

Before we jump into the details of action metadata, it might be helpful to examine our workflow to understand the order that things happen. I have attached a screenshot below of the most recent workflow run, you can also follow along by clicking on the Actions tab for your repository.

Notice that our third workflow step, the one that is looking for our action is failing. We expect this, but the magic ✨is in the error message!

That step is looking for a file named action.yml.

Because action.yml is non-existent in the hello-world directory we see this error. So let's start by talking about, and creating, the missing action.yml file.

[github-learning-lab]

Action metadata

Every GitHub Action that we write needs to be accompanied by a metadata file. This file has a few rules to it, lets outline those now:

• Filename must be action.yml
• Required for both Docker container and JavaScript actions
• Written in YAML syntax

This file defines the following information about your action:

Parameter	Description	Required
Name	The name of your action. Helps visually identify the actions in a job.	✅
Description	A summary of what your action does.	✅
Inputs	Input parameters allow you to specify data that the action expects to use during runtime. These parameters become environment variables in the runner.	❌
Outputs	Specifies the data that subsequent actions can use later in the workflow after the action that defines these outputs has run.	❌
Runs	The command to run when the action executes.	✅
Branding	You can use a color and Feather icon to create a badge to personalize and distinguish your action in GitHub Marketplace.	❌

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📖Read more about Action metadata

[github-learning-lab]

Enough talk, lets do this!

Now that we know what action metadata is, let's create the metadata for our current hello-world action.

⌨️ Activity: Create the metadata file

💡All of the following steps take place inside of the .github/actions/hello-world directory.

We will start with using the parameters that are required and later implement some optional parameters as our action evolves.

1. Create a new file in: .github/actions/hello-world/action.yml
2. Add the following contents to the .github/actions/hello-world/action.yml file:

   name: "my hello action"
   
   description: "say hello with GitHub Actions"
   
   runs:
     using: "node12"
     main: "main.js"

3. Save the action.yml file
4. Commit the changes and push them to the hello-world branch:

   git add action.yml
   git commit -m 'create action.yml'
   git push

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I'll respond here once I notice that you've pushed your changes.