Using yq4 to check for child element?

[simon-anz]

Have a structure

---

items:

• type: t1
  metadata: m1
• type: t2
  metadata: m2
• type: t3

---

Want to emit item.type only when metadata is not present.

When present seems to work OK

$ yq4 eval '.items[] | select(.metadata) .type' dummy.yaml
t1
t2

But couldn't find how to invert selector. Using length looked like it should work:

$ yq4 eval '.items[] | .metadata | length == 0' dummy.yaml
false
false
true

but didn't??

$ yq4 eval '.items[] | select(.metadata | length == 0) .type' dummy.yaml
$

[simon-anz]

Ah, I just found "has", and when combined with |not, seems to do OK.

$ yq4 eval '.items[] | select(has("metadata") | not) .type' dummy.yaml
t3

[simon-anz]

How might I use"delete" to remove items 1 and 2 from the list, leaving t3 in place?

[mikefarah]

yq e 'del(.items[] | select(has("metadata")))'  dummy.yaml

[simon-anz]

Thanks! Is there a way to look deeper than one level with "has"? My contrived example is a little simpler than my real case :)

I want to leave only items that are type=Opaque AND does not have .metadata.ownerReferences

So only the second item below should be left

---

apiVersion: v1
items:

• apiVersion: v1
  metadata:
  ownerReferences:
  • apiVersion: bitnami.com/v1alpha1
    type: Opaque
• apiVersion: v1
  metadata:
  name: aegis-ingressgateway-service-account-token-gcp69
  type: Opaque
• apiVersion: v1
  metadata:
  name: aegis-ingressgateway-service-account-token-gcp69
  type: kubernetes.io/service-account-token
• apiVersion: v1
  metadata:
  name: aegis-ingressgateway-service-account-token-gcp69
  ownerReferences:
  • apiVersion: bitnami.com/v1alpha1
    type: kubernetes.io/service-account-token

---

I can do the type filter with
'del(.items[] | select(.type=="Opaque" | not))'

And could do a single-level "has", but... 🤯

[mikefarah]

Sure, just pipe the parent expression into 'has', e.g:

'.items[] | select(.metadata | has("ownerReferences"))'

You will need to use and/or (https://mikefarah.gitbook.io/yq/operators/boolean-operators) to combine the type selection with has

[simon-anz]

WIN!

$ yq4 e 'del(.items[] | select(.type=="Opaque" | not)) | del(.items[] | select(.metadata | has("ownerReferences")))' dummy2.yaml
apiVersion: v1
items:
  - apiVersion: v1
    metadata:
      name: aegis-ingressgateway-service-account-token-gcp69
    type: Opaque

[simon-anz]

Thanks @mikefarah !!