Update 4-custom-transformers.md

circle_ci/4-custom-transformers.md

@@ -18,7 +18,7 @@ In this lab you will build upon the `dry-run` command to override Valet's defaul
 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:
 
 ```bash
-# ADD_COMMAND
+gh valet dry-run circle-ci -o tmp/custom_transformers --circle-ci-project circleci-node-example
 ```
 
 The converted workflow that is generated by the above command can be seen below:
@@ -27,7 +27,35 @@ The converted workflow that is generated by the above command can be seen below:
   <summary><em>Converted workflow 👇</em></summary>
 
 ```yaml
-# ADD_YAML
+name: labs-data/circleci-node-example/sample
+on:
+  push:
+    branches:
+    - main
+jobs:
+  setup:
+    runs-on:
+      - self-hosted
+      - large
+    env:
+      COVERAGE_DIR: "./tmp/cov"
+    steps:
+    - run: mkdir -p $COVERAGE_DIR
+  node_test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - id: npm-cache-dir
+      run: echo "::set-output name=dir::$(npm config get cache)"
+    - uses: actions/cache@v2
+      with:
+        path: "${{ steps.npm-cache-dir.outputs.dir }}"
+        key: "${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}"
+        restore-keys: "${{ runner.os }}-node-"
+    - run: npm ci
+    - run: npm run test
+#     # This item has no matching transformer
+#     - codecov_codecov_upload:
 ```
 
 </details>
@@ -36,7 +64,67 @@ _Note_: You can refer to the previous [lab](./3-dry-run.md) to learn about the f
 
 ## Custom transformers for an unknown step
 
-ADD_CONTENT_OR_REMOVE
+The converted workflow above contains an `codecov_codecov_upload` 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?
+    - __codecov_codecov_upload__
+
+2. What is the desired Actions syntax to use instead?
+    - After some research, you have determined that the [codecov action](https://github.com/marketplace/actions/codecov) in the marketplace will provide similar functionality:
+
+      ```yaml
+      - uses: codecov/codecov-action@v3
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+      ```
+
+Now you can begin to write the custom transformer. Custom transformers use a DSL built on top of Ruby and should be defined in a file with the `.rb` file extension. You can create this file by running the following command in your codespace terminal:
+
+```bash
+code transformers.rb
+```
+
+Next, you will define a `transform` method for the `codecov_codecov_upload` identifier by adding the following code to `transformers.rb`:
+
+```ruby
+transform "codecov_codecov_upload" do |_item|
+  {
+    name: "Upload coverage to Codecov",
+    uses: "codecov/codecov-action@v3",
+    with: { 
+      token: "${{ secrets.CODECOV_TOKEN }}" 
+    }
+  }
+end
+```
+
+This method can use any valid ruby syntax and should return a `Hash` that represents the YAML that should be generated for a given step. Valet will use this method to convert a step with the provided identifier and will use the `item` parameter for the original values configured in CircleCI.
+
+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:
+
+```bash
+gh valet dry-run circle-ci -o tmp/custom_transformers --circle-ci-project circleci-node-example --custom-transformers transformers.rb
+```
+
+The converted workflow that is generated by the above command will now use the custom logic for the `codecov_codecov_upload` step.
+
+```diff
+- #     # This item has no matching transformer
+- #     - codecov_codecov_upload:
++ - name: upload coverage to Codecov
++   uses: codecov/codecov-action@v3
++     with:
++       token: "${{ secrets.CODECOV_TOKEN }}"
+```
+
+_Note_: 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:
+
+```ruby
+transform "codecov_codecov_upload" do |item|
+  puts item
+end
+```
+
 
 ## Custom transformers for environment variables