Server-Side Diff breaks Ingress modifications

[jocelynthode]

Checklist:

• I've searched in the docs and FAQ for my answer: https://bit.ly/argocd-faq.
• I've included steps to reproduce the bug.
• I've pasted the output of argocd version.

Describe the bug

Due to us enabling strict-validate-path-type in ingress-nginx, we had to modify some PathType in our Ingresses managed by helm via argocd. However argocd breaks when server-side diff is enabled.

To Reproduce

• Enable controller.diff.server.side: 'true'
• Try to refresh an application based on a helm chart that has an ingress with a PathType change
• ArgoCD fails with:

unmarshal error: invalid character '.' after top-level value


Failed to compare desired state to live state: failed to calculate diff: error calculating server side diff: serverSideDiff error: error converting json string to unstructured for resource Ingress/xxx: unmarshal error: invalid character '.' after top-level value

Here is an example Ingress where we have the issue:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    argocd.argoproj.io/tracking-id: xxx_xxx:networking.k8s.io/Ingress:xxx/xxx-vcs-healthz
    cert-manager.io/cluster-issuer: letsencrypt-prod
    cert-manager.io/private-key-algorithm: ECDSA
    ingressClassName: nginx
    nginx.ingress.kubernetes.io/force-ssl-redirect: "true"
    nginx.ingress.kubernetes.io/whitelist-source-range: 0.0.0.0/0,::/0
  name: xxx-vcs-healthz
  namespace: xxx
spec:
  ingressClassName: nginx
  rules:
  - host: xxx.example.com
    http:
      paths:
      - backend:
          service:
            name: keda-interceptor
            port:
              number: 8080
        path: /vcs_branch_sha.txt
        pathType: Prefix
  tls:
  - hosts:
    - xxx.example.com
    secretName: xxx.example.com

Disabling the server-side diff via the annotation argocd.argoproj.io/compare-options: ServerSideDiff=false fixes the issue.

Expected behavior

ArgoCD should apply the resource with no issue

Version

{
    "Version": "v2.13.3+a25c8a0",
    "BuildDate": "2025-01-03T18:44:26Z",
    "GitCommit": "a25c8a0eef7830be0c2c9074c92dbea8ff23a962",
    "GitTreeState": "clean",
    "GoVersion": "go1.23.1",
    "Compiler": "gc",
    "Platform": "linux/amd64",
    "KustomizeVersion": "v5.4.3 2024-07-19T16:40:33Z",
    "HelmVersion": "v3.15.4+gfa9efb0",
    "KubectlVersion": "v0.31.0",
    "JsonnetVersion": "v0.20.0"
}