Fix vMCP podTemplateSpec when only pod-level settings is applied #2897
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When users provided a PodTemplateSpec with only pod-level settings (like nodeSelector), the Deployment creation failed because containers were being wiped out. Root cause: The code parsed user JSON into a Go struct then re-marshaled it. Go's json.Marshal converts nil slices to [], which strategic merge patch interprets as "replace with empty array" - removing the vmcp container. Fix: Use the raw JSON bytes directly from Spec.PodTemplateSpec.Raw instead of re-marshaling, preserving exactly what the user specified.
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…cklok#2897) * Fix PodTemplateSpec strategic merge wiping containers When users provided a PodTemplateSpec with only pod-level settings (like nodeSelector), the Deployment creation failed because containers were being wiped out. Root cause: The code parsed user JSON into a Go struct then re-marshaled it. Go's json.Marshal converts nil slices to [], which strategic merge patch interprets as "replace with empty array" - removing the vmcp container. Fix: Use the raw JSON bytes directly from Spec.PodTemplateSpec.Raw instead of re-marshaling, preserving exactly what the user specified. * Add integration test for the vMCP podTemplateSpec
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This PR fixes a bug where applying a PodTemplateSpec with only pod-level settings would accidentally wipe out the controller-generated vmcp container.
The root cause was Go's JSON marshaling behavior - when we parsed the user's JSON into Go structs and re-marshaled it, nil slices became empty arrays ([]), which strategic merge patch interpreted as "delete all containers".
The fix is: we now use the raw JSON bytes directly from the user's PodTemplateSpec for the strategic merge patch, preserving exactly what they specified without any round-trip through Go structs.
I also added a regression test that explicitly verifies the container is preserved when only a nodeSelector is provided, improved error handling in the integration tests, and fixed an edge case for empty raw bytes.