How to get key and value with yq V4.x.x

We have upgraded yq from version 3.x.x to version 4.x.x and there is a part that does not work the same when getting a key value from the following structure:

key: a
value:
  enabled: true
  project: ../../a
  version: v1.1.1
  persistence: true
key: b
value:
  enabled: true
  project: ../../b
  version: v1.1.1
  persistence: true
key: c
value:
  enabled: true
  project: ../../c
  version: v1.1.1
  persistence: false

With the following yq command I would get the following

"a": true, "b": true, "c": false

This is the command

yq '.applications | to_entries | .[] | select(.value.enabled == true) .key, .value.persistence' manifest.yml

and now the command returns this

a
b
c
null

I have recently started using yq and I really can't understand it.

Solution

There are two things going on here. First, I think the data structure you've presented in your question is erroneous; looking at the filter you're trying to run, I think the original data structure looks like this:

applications:
  a:
    enabled: true
    project: ../../a
    version: v1.1.1
    persistence: true
  b:
    enabled: true
    project: ../../b
    version: v1.1.1
    persistence: true
  c:
    enabled: true
    project: ../../c
    version: v1.1.1
    persistence: false

If we apply your filter using kislyuk/yq, then we see the following output:

"a"
true
"b"
true
"c"
false

On the other hand, we if use mikefarah/yq, we get:

a
b
c
null

This is because these two commands are different. The first is a simple Python wrapper for the jq command, whereas the second is a standalone Go binary. They support different syntax.

You cannot "upgrade" from the kislyuk version (latest version: 3.1.0) to the mikefarah version (latest version: 4.30.8).