Execute github actions workflow/job in directory where code was changed - github

Question

I am trying to implement a github actions workflow with a job which will plan and apply my terraform code changes only for directory where changes were made. The problem I am currently facing is that I can't figure out how to switch directories so that terraform plan is executed from a directory where code has been updated/changed.
I have a monorepo setup which is as follow:
repo
tf-folder-1
tf-folder-2
tf-folder-3
Each folder contains an independent terraform configuration. So, for example I would like run a workflow only when files change inside tf-folder-1. Such workflow needs to switch to working directory which is tf-folder-1 and then run terraform plan/apply.
jobs:
terraform:
name: "Terraform"
runs-on: ubuntu-latest
defaults:
run:
working-directory: ./tf-folder-1
steps:
- name: Checkout
uses: actions/checkout#v3
- name: Configure AWS credentials from Test account
uses: aws-actions/configure-aws-credentials#v1
with:
role-to-assume: arn:aws:iam::000000000000000:role/deploy-role
aws-region: eu-west-2
- name: Setup Terraform
uses: hashicorp/setup-terraform#v2
...
So far, I have the above terraform job but it only runs for statically defined working-directory. It doesn't work with a use case where it should run the workflow when changes happen within specific folder. Can someone advise how to fix this pipeline?
Thanks

Answer 1

GitHub Actions has path filtering you can take advantage of when you are working with workflows that are triggered off a push or push_request event.
For example say you have a monorepo with the directories, tf_1, tf_2, and tf_3. You can do something like below for when changes occur to the directory tf_1.
name: Demonstrate GitHub Actions on Monorepo
on:
push:
branches:
- master
paths:
- 'tf_1/**'
defaults:
run:
working-directory: tf_1
jobs:
build:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout#v1
For more details on path filtering, please refer to the GitHub Actions syntax documentation.

Answer 2

You can use a GitHub action that outputs the directories where the files have changed/modified, for example, this one: Changed-files or even perform the calculation with a shell step using git diff.
If you use the GHA suggested you can set the input dir_names to true, which would output unique changed directories instead of filenames, based on the results of that you can change the directory to run your Terraform operations.

Answer 3

Here is the solution to run multiple jobs based on number of directories that have been update.
In the below snippet you can see directories job which will check which directories have been updated, later it output an array or switch which is then used in matrix strategy for terraform job.
jobs:
directories:
name: "Directory-changes"
runs-on: ubuntu-latest
steps:
- uses: theappnest/terraform-monorepo-action#master
id: directories
with:
ignore: |
aws/**/policies
aws/**/templates
aws/**/scripts
- run: echo ${{ steps.directories.outputs.modules }}
outputs:
dirs: ${{ steps.directories.outputs.modules }}
terraform:
name: "Terraform"
runs-on: ubuntu-latest
needs: directories
strategy:
matrix:
directories: ${{ fromJson(needs.directories.outputs.dirs) }}
defaults:
run:
working-directory: ${{ matrix.directories }}
steps:
- name: Checkout
uses: actions/checkout#v3
- name: Setup Terraform
uses: hashicorp/setup-terraform#v2
with:
cli_config_credentials_token: ${{ secrets.TF_CLOUD_TEAM_API_TOKEN_PREPROD }}
- name: Terraform Format
id: fmt
run: terraform fmt -check
- name: Terraform Init
id: init
run: terraform init
- name: Terraform Validate
id: validate
run: terraform validate -no-color
- name: Terraform Plan
id: plan
if: github.event_name == 'pull_request'
run: terraform plan -no-color -input=false
continue-on-error: true