yq: how to read a sibling element value? - yaml

Question

I am exploring yq to modify my YAML where I want to add a new element under spec of the ImageStream with name == openshift45
apiVersion: v1
items:
- apiVersion: image.openshift.io/v1
kind: ImageStream
metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
creationTimestamp: null
labels:
app: openshift45
app.kubernetes.io/component: openshift45
app.kubernetes.io/instance: openshift45
name: nodejs-10
spec:
lookupPolicy:
local: false
tags:
- annotations:
openshift.io/imported-from: registry.access.redhat.com/ubi8/nodejs-10
from:
kind: DockerImage
name: registry.access.redhat.com/ubi8/nodejs-10
generation: null
importPolicy: {}
name: latest
referencePolicy:
type: ""
status:
dockerImageRepository: ""
- apiVersion: image.openshift.io/v1
kind: ImageStream
metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
creationTimestamp: null
labels:
app: openshift45
app.kubernetes.io/component: openshift45
app.kubernetes.io/instance: openshift45
name: openshift45
spec:
lookupPolicy:
local: false
status:
dockerImageRepository: ""
The below command returns the valid metadata element. Now, I want to move to the parent and then pick spec. Is this possible with yq - https://github.com/mikefarah/yq?
yq r openshift45.yaml --printMode pv "items(kind==ImageStream).(name==openshift45)"
returns
items.[1].metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
creationTimestamp: null
labels:
app: openshift45
app.kubernetes.io/component: openshift45
app.kubernetes.io/instance: openshift45
name: openshift45
Expected output:
apiVersion: v1
items:
- apiVersion: image.openshift.io/v1
kind: ImageStream
metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
creationTimestamp: null
labels:
app: openshift45
app.kubernetes.io/component: openshift45
app.kubernetes.io/instance: openshift45
name: nodejs-10
spec:
lookupPolicy:
local: false
tags:
- annotations:
openshift.io/imported-from: registry.access.redhat.com/ubi8/nodejs-10
from:
kind: DockerImage
name: registry.access.redhat.com/ubi8/nodejs-10
generation: null
importPolicy: {}
name: latest
referencePolicy:
type: ""
status:
dockerImageRepository: ""
- apiVersion: image.openshift.io/v1
kind: ImageStream
metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
creationTimestamp: null
labels:
app: openshift45
app.kubernetes.io/component: openshift45
app.kubernetes.io/instance: openshift45
name: openshift45
spec:
*dockerImageRepository: <$MYREGISTRY>/<$MYNAMESPACE>/<$MYPROJECT>*
lookupPolicy:
local: false
status:
dockerImageRepository: ""

Answer 1

The Path Expressions in mikefarah/yq is not quite documented to show a real example of how to use multiple conditions to get to the desired object. So for the YAML in question, using one unique condition you could do something like below. Verified in yq version 3.3.2
yq w openshift45.yaml 'items.(metadata.name == openshift45).spec.dockerImageRepository' '<$MYREGISTRY>/<$MYNAMESPACE>/<$MYPROJECT>'
You can use the -i flag along with write to modify the YAML in-place. See Updating files in-place
If this isn't desired and you need multiple conditional selection to get to the desired object, suggest raising a issue at the GitHub page - https://github.com/mikefarah/yq/issues requesting the right syntax for the same.

Answer 2

Currently it is not possible in yq. You will have to get the output of first command in a variable and pass that variable to next one.
yq is a wrapper on jq but it doesn't have the functionality of custom functions. Custom functions make it possible to use any value from any hierarchy of the document at one place.
Thanks to Inian for pointing out that OP is not using the wrapper yq version. Unfortunately, the version used also doesn't allow using custom functions for now.