[slamdev]

Problem

Since #923, when the chart is unchanged, createPatch builds the desired state of a custom resource as jsonpatch.MergePatch(current, new). A JSON merge patch reads null as "delete this key". Every explicit null a chart renders therefore shows as a removal under --three-way-merge, even though nothing has drifted: the chart is unchanged, so the upgrade sends no patch for the field, and the live object keeps it.

This is common with charts that build a CR spec from defaults files. For example, grafana/k8s-monitoring 3.8.5 renders its Alloy CRs with configMap.key: null, image.digest: null, podDisruptionBudget.minAvailable: null and more. Every plan then shows on each collector:

monitoring, k8s-monitoring-alloy-logs, Alloy (collectors.grafana.com) has changed:
-       key: null
-       name: null
-     digest: null
-     terminationGracePeriodSeconds: null
...

Fix

In the chart-unchanged path, drop the null-valued keys from the new manifest's objects before the merge. A null the chart renders leaves the field unset, so the live value, null or otherwise, is kept. Lists are left as they are, since a merge patch replaces them whole.

Tests

Two cases in TestCreatePatchForUnstructured, both with the chart unchanged:

• a null in both manifests and stored live → no change
• a null in both manifests where live has a value → no change

go test ./... passes. I also checked against a live cluster: the Alloy diffs above are gone, and a real manual edit on a PrometheusRule is still reported.

A related gap I left out of scope: a null inside a list element still reads as a change, because MergePatch prunes nulls inside the patch's lists as well.

[Copilot]

🟢 Approval recommended

No active review issues were identified for the custom-resource null-handling changes.

No open issues 🎉

What changed in this PR

This PR refines three-way merge handling for custom resources so unchanged chart-rendered nulls are not reported as drift, while preserving live values.

Changes:

• Remove null-valued object keys before building the desired state when the chart is unchanged; leave lists untouched.
• Add regression tests for chart-rendered nulls where the live field contains either null or a value.

File	Description
manifest/​generate.go	Adds recursive null-key removal to the chart-unchanged merge path.
manifest/​generate_test.go	Adds two regression cases covering preservation of live fields.

_{Review effort: Balanced}