Question / issue : '--exclude' failing when used on KUBECTL_EXTERNAL_DIFF

[alvarogonzalez-packlink]

So I'm using dyff between as a KUBECTL_EXTERNAL_DIFF, and in general it works correctly like this:

❯ export KUBECTL_EXTERNAL_DIFF="dyff between -b "
❯ kubectl -n tools diff -f ./mongodb-cronjob.yaml

metadata.generation
  ± value change
    - 24
    + 25

spec.jobTemplate.spec.template.spec.containers.mongo.image
  ± value change
    - some/mongoimage:1.3.0
    + some/mongoimage:1.4.0

But I wanted to remove the metadata.generation changes, so I added an --exclude option. But then it fails to work:

❯ export KUBECTL_EXTERNAL_DIFF="dyff between -b --exclude 'metadata.generation'"
❯ kubectl -n tools diff -f ./mongodb-cronjob.yaml
╭ Error occurred
│ accepts 2 arg(s), received 1
╵

When I use it on that same yaml on disk, it works properly:

❯ dyff between -b --exclude "metadata.generation" mongo1.yaml mongo2.yaml

spec.jobTemplate.spec.template.spec.containers.mongo.image
  ± value change
    - some/mongoimage:1.3.0
    + some/mongoimage:1.4.0

Testing

• dyff version 1.10.2
• macOS 15.7.1 ARM
• kubectl version
  Client Version: v1.33.3
  Kustomize Version: v5.6.0
  Server Version: v1.32.8-gke.1170000
• I've tried a bunch of different escaping and quoting options for the exclude parameter, like \"metadata.generation\" or "metadata.generation", but cannot remember all of them... 😬

Question

• Am I maybe breaking Kubernetes object detection with the exclude option?
• Can I setup any debug mode that shows me the full command line kubectl is passing to dyff ?
  Adding the --v 9 verbose lebel to kubectl shows tracing and API calls, but not dyffcalls
• Am I missing something?

[nicknovitski]

I'm dealing with this currently. It's probably because of the filter that kubectl puts on the value of KUBECTL_EXTERNAL_DIFF.

If I understand this code correctly, it looks at each word (space-separated) in the variable, and discards any that contain characters besides alphanumerics, -, or =: https://github.com/kubernetes/kubectl/blob/9978cf7c5f8319b783ba044c2f226753f9c30fef/pkg/cmd/diff/diff.go#L193-L202

You may find that the command works if you make the parameter just generation, without any . characters. Another workaround you can do is write a script which runs dyff with the exclude arguments you prefer, and set KUBECTL_EXTERNAL_DIFF to that script.