Update a new element if some condition is met

[sgandon]

Hello and happy to be the first to use this discussion feature.
I am using a for loop to update many yaml files and I'd like to find a yq expression to only update the metadata.name value if the kind == "Namespace" and not update the file if not.
here the yaml file I'd like to update.

apiVersion: v1
kind: Namespace
metadata:
  name: foo

Is it possible with yq 4 ?

[mikefarah]

I've got:

yq e '(select(.kind == "Namespace") | .metadata.name) = "meow"' sample.yaml

[mikefarah]

Also - the title says 'add' but the description is 'update'? I'm assuming the description is right (could you update the title?)

[dlampa]

Thanks a lot, this has helped me a lot. Could you perhaps provide an explanation of the expression syntax, i.e. what is the significance of having ( ) around on the LHS of the assignment when referring to the example:

foo: bar
bar: baz
items:
  - item:
      name: foo
  - item:
      name: abc
  - item:
      name: def
something else: foobar

yq e '(.items.[] | select(.item.name=="foo") | .item.address) ="test" ' sample.yml
vs.
yq e '.items.[] | select(.item.name=="foo") | .item.address="test" ' sample.yml

Thanks!!

[sgandon]

Thanks a lot for your answer, and I'll change the title.
In fact I have the 3 following requirements : update, add and remove one attribute base on a selected node. But from your suggestion, I figured the rest.