In this lab you will build upon the `dry-run` command to override GitHub Actions Importer's default behavior and customize the converted workflow using "custom transformers". Custom transformers can be used to:
4. Convert references to runners to use a different runner name in Actions.
## Prerequisites
1. Followed the steps [here](./readme.md#configure-your-codespace) to set up your GitHub Codespaces environment.
2. Completed the [configure lab](./1-configure.md#configuring-credentials).
3. Completed the [dry-run lab](./3-dry-run.md).
## Perform a dry-run
You will be performing a `dry-run` command to inspect the workflow that is converted by default. Run the following command within the codespace terminal:
_Note_: You can refer to the previous [lab](./3-dry-run.md) to learn about the fundamentals of the `dry-run` command.
## Custom transformers for an unknown step
The converted workflow above contains an `codedeploy` step that was not automatically converted. Answer the following questions before writing a custom transformer:
1. What is the "identifier" of the step to customize?
- __codedeploy__
2. What is the desired Actions syntax to use instead?
- After some research, you have determined that we can login to AWS with the `aws-actions/configure-aws-credentials@v1` action, and deploy the app to AWS using a run step to replace the functionality of `codedeploy`:
```yaml
- uses: aws-actions/configure-aws-credentials@v1
with:
role-to-assume: owner
role-session-name: GitHub-Action-Role
aws-region: east-2
- run: |
echo "Deploying branch ${{ env.GITHUB_REF }} to ${{ github.event.inputs.environment }}"
Now you can begin to write the custom transformer. Custom transformers use a DSL built on top of Ruby and should be defined in a file with the `.rb` file extension. You can create this file by running the following command in your codespace terminal:
This method can use any valid ruby syntax and should return a `Hash`, or an array of `Hashes` that represent the YAML that should be generated for a given step. GitHub Actions Importer will use this method to convert a step with the provided identifier and will use the `item` parameter for the original values configured in Travis CI.
Now you can perform another `dry-run` command and use the `--custom-transformers` CLI option to provide this custom transformer. Run the following command within your codespace terminal:
_Note_: We hard coded certain values such as the `application-name`, but we can apply these properties programmatically as well by using the item passed into the transform method. If you were unsure what the data structure of `item` was, you could use the following code in the custom transformer to print `item` to the console:
You can use custom transformers to edit the values of environment variables in converted workflows. In this example, you will update the `DB` environment variable to be `sqlite` instead of `mysql`.
To do this, add the following code to the `transformers.rb` file.
```ruby
env "DB", "sqlite"
```
In this example, the first parameter to the `env` method is the environment variable name and the second is the updated value.
Now you can perform another `dry-run` command with the `--custom-transformers` CLI option. When you open the converted workflow the `DB` environment variable will be set to `sqlite`:
```diff
env:
- DB: "mysql"
+ DB: "sqlite"
```
## Custom transformers for runners
Finally, you can use custom transformers to dictate which runners converted workflows should use. First, answer the following questions:
1. What is the label of the runner in Travis to update?
Now you can perform another `dry-run` command with the `--custom-transformers` CLI option. When you open the converted workflow, the `runs-on` statement will use the customized runner labels:
