Run Google Cloud Build Command for Each Result of Array - google-cloud-build

Question

I have an Nx workspace with multiple Angular apps included. When master is updated in my GitHub repo, I want a build to kick off. That part is easy enough with GCB's triggers. But what I want to happen is to run this command:
npm run affected:apps
on the trigger, and build a Docker image and push it to Google Container registry for each affected app. My cloudbuild.yaml file looks like this so far:
steps:
- name: 'gcr.io/cloud-builders/git'
args: ['fetch', '--unshallow']
- name: node:10.15.1
entrypoint: npm
args: ['run affected:apps --base=origin/master --head=HEAD']
That command returns a result like this:
> project-name#0.0.0 affected:apps /Users/username/projects/project-folder
> nx affected:apps
Note: Nx defaulted to --base=master --head=HEAD
my-app-1
I'm not sure what to do with Google Cloud with that result. With a node script, I could do the following to print out an array of affected apps:
const { exec } = require('child_process');
function getApps() {
exec('npm run affected:apps', (err, out) => {
if (err) {
console.log(null);
} else {
const lines = out.split('\n');
const apps = lines[lines.length - 2].split(' ');
console.log(JSON.stringify(apps));
}
});
}
getApps();
That returns an array of the affected apps, and null if an error. Still, even with that, I'm not sure what I would do for the next step in Google Cloud build. With the results of either the command or that script, ideally I'd be able to run a docker build command, like this:
docker build --file ./:loop variable:/Dockerfile
where :loop variable: is the name of an affected app. I'd like to do that for each value in the array, and not do anything if, for some reason, the command returns no affected apps.
Any ideas on how to use Google Cloud Build with Nx Workspaces, or if you've just got Google Cloud build experience and know what my next step should be, that'd be great.

Answer 1

Continue #chinoche comment there is an example of how you could save the list of affected apps to the affected.txt file
- name: 'gcr.io/cloud-builders/npm'
entrypoint: 'bash'
args:
- '-c'
- |
IFS=' ' read -a apps <<< $(npx nx affected:apps --base=origin/master~1 --plain)
for app in "${apps[#]}"
do
echo $app
done >> affected.txt
The next step could read the file and call any other commands, e.g. create docker image
- name: 'gcr.io/cloud-builders/docker'
entrypoint: 'bash'
args:
- '-c'
- |
while IFS= read -r project; do
docker build -t gcr.io/$PROJECT_ID/$project -f <path-to>/Dockerfile .
done < affected.txt
One of the tricks might be to create separate cloudbuild.yaml file for each project and then trigger a new cloud build process for each affected project. That allows having a completely different build process for each project.
- name: 'gcr.io/cloud-builders/gcloud'
entrypoint: 'bash'
args:
- '-c'
- |
while IFS= read -r project; do
gcloud builds submit --config ./<path-to>/$project/project-specific-cloudbuild.yaml .
done < affected.txt

Answer 2

if you are able to get the affected apps with the node script I'd suggest you to write a file with the affected apps in a Cloud Build custom steps, this file will be written at the "/workspace" directory and will be able to any other custom step that may be executed in later steps, with this you should be able to run the docker build command