Add or Update object in array in JSON using jq - json

Question

I'm trying to use jq to parse a JSON (the output of the OpenShift oc process ... command, actually), and add/update the env array of a container with a new key/value pair.
Sample input:
{
"kind": "List",
"apiVersion": "v1",
"metadata": {},
"items": [
{
"apiVersion": "v1",
"kind": "Service",
"metadata": {
"annotations": {
"description": "Exposes and load balances the node.js application pods"
},
"name": "myapp-web"
},
"spec": {
"ports": [
{
"name": "web",
"port": 3000,
"protocol": "TCP",
"targetPort": 3000
}
],
"selector": {
"name": "myapp"
}
}
},
{
"apiVersion": "v1",
"kind": "Route",
"metadata": {
"name": "myapp-web"
},
"spec": {
"host": "app.internal.io",
"port": {
"targetPort": "web"
},
"to": {
"kind": "Service",
"name": "myapp-web"
}
}
},
{
"apiVersion": "v1",
"kind": "DeploymentConfig",
"metadata": {
"annotations": {
"description": "Defines how to deploy the application server"
},
"name": "myapp"
},
"spec": {
"replicas": 1,
"selector": {
"name": "myapp"
},
"strategy": {
"type": "Rolling"
},
"template": {
"metadata": {
"labels": {
"name": "myapp"
},
"name": "myapp"
},
"spec": {
"containers": [
{
"env": [
{
"name": "A_ENV",
"value": "a-value"
}
],
"image": "node",
"name": "myapp-node",
"ports": [
{
"containerPort": 3000,
"name": "app",
"protocol": "TCP"
}
]
}
]
}
},
"triggers": [
{
"type": "ConfigChange"
}
]
}
}
]
}
In this JSON, I want to do the following:
Find the DeploymentConfig object
Check if it has the env array in the first container
If it does, add a new object {"name": "B_ENV", "value": "b-value"} in it
If it does not, add the env array, with the object {"name": "B_ENV", "value": "b-value"} in it
So far, I'm able to tackle part of this, where I'm able to find the concerned object, and add the new env var to the container:
oc process -f <dc.yaml> -o json | jq '.items | map(if .kind == "DeploymentConfig"
then .spec.template.spec.containers[0].env |= .+ [{"name": "B_ENV", "value": "b-value"}]
else .
end)'
This is able to insert the new env var as expected, but the output is an array as shown below. Also, it doesn't handle the part where the env array may not be there at all.
I want to be able to produce the same output as the input, but with the new env var added.
Sample output:
[
{
"apiVersion": "v1",
"kind": "Service",
"metadata": {
"annotations": {
"description": "Exposes and load balances the node.js application pods"
},
"name": "myapp-web"
},
"spec": {
"ports": [
{
"name": "web",
"port": 3000,
"protocol": "TCP",
"targetPort": 3000
}
],
"selector": {
"name": "myapp"
}
}
},
{
"apiVersion": "v1",
"kind": "Route",
"metadata": {
"name": "myapp-web"
},
"spec": {
"host": "app.internal.io",
"port": {
"targetPort": "web"
},
"to": {
"kind": "Service",
"name": "myapp-web"
}
}
},
{
"apiVersion": "v1",
"kind": "DeploymentConfig",
"metadata": {
"annotations": {
"description": "Defines how to deploy the application server"
},
"name": "myapp"
},
"spec": {
"replicas": 1,
"selector": {
"name": "myapp"
},
"strategy": {
"type": "Rolling"
},
"template": {
"metadata": {
"labels": {
"name": "myapp"
},
"name": "myapp"
},
"spec": {
"containers": [
{
"env": [
{
"name": "A_ENV",
"value": "a-value"
},
{
"name": "B_ENV",
"value": "b-value"
}
],
"image": "node",
"name": "myapp-node",
"ports": [
{
"containerPort": 3000,
"name": "app",
"protocol": "TCP"
}
]
}
]
}
},
"triggers": [
{
"type": "ConfigChange"
}
]
}
}
]
Is this doable, or is it too much to do with jq, and I should probably do this in python or node?
EDIT 1:
I just realized that conditional add/update of env array is already handled by the |= syntax!
So, I basically just need to be able to get the same structure back as the input, with the relevant env var added in the concerned array.

Answer 1

You pretty much had it, but you'll want to restructure your filter to preserve the full results. You want to make sure that none of the filters changes the context. By starting off with .items, you changed it from your root object to the items array. That in of itself is not so much a problem but what you do with that matters. Keep in mind that assignments/updates preserves the original context as a result with the change applied. So if you wrote your filter in terms of an update, it will work for you.
So to do this, you'll want to find the env array of the first container in the DeploymentConfig item. First let's find that:
.items[] | select(.kind == "DeploymentConfig").spec.template.spec.containers[0].env
You don't need to do anything else in terms of error handling since select will simply produce no result. From there, you just need to update the array by adding the new value.
(.items[] | select(.kind == "DeploymentConfig").spec.template.spec.containers[0].env) +=
[{name:"B_ENV",value:"b-value"}]
If the array exists, it will add the new item. If not, it will create a new env array. If env is not an array, that would be a different problem.