forceUpdate: true clears Helm parameters when there is no tag in registry, causing invalid image reference

[papaslon]

Describe the bug

When forceUpdate: true is set in the ImageUpdater CRD, argocd-image-updater sets Helm parameter (global.image.tag) to empty when there is no image tag specified in the Artifact Registry's imageName field. This causes a syntax error because the resulting image reference becomes invalid (e.g., registry/image: with an empty tag). Additionally, argocd-image-updater removes the global.image.tag Helm parameter that was explicitly set in the ArgoCD Application manifest.

Previously, the image updater would preserve the existing global.image.tag value even when there was no specified image tag in Artifact Registry.

To Reproduce

1. Create an ArgoCD Application manifest with global.image.tag set as a Helm parameter:

   apiVersion: argoproj.io/v1alpha1
   kind: Application
   metadata:
     name: example-app
   spec:
     project: preview
     source:
       repoURL: https://github.com/org/repo.git
       path: infrastructure/helm/frontend
       targetRevision: test
       helm:
         valueFiles:
           - ../envs/frontend-partners/values-preview.yaml
         parameters:
           - name: global.image.tag
             value: "mq@sha256:123456"
             forceString: true

2. Create an ImageUpdater CRD with forceUpdate: true and an imageName that doesn't include a tag:

   apiVersion: argocd-image-updater.argoproj.io/v1alpha1
   kind: ImageUpdater
   metadata:
     name: example-image-updater
   spec:
     namespace: argocd
     commonUpdateSettings:
       forceUpdate: true
       updateStrategy: "digest"
     writeBackConfig:
       method: "argocd"
     applicationRefs:
       - namePattern: "example-app"
         images:
           - alias: frontend-partners
             imageName: "example-registry/docker/frontend-partners"
             manifestTargets:
               helm:
                 name: "global.image.name"
                 tag: "global.image.tag"

3. Apply both resources to the cluster

4. Observe that argocd-image-updater removes the global.image.tag parameter from the Application manifest

5. Observe the error when ArgoCD tries to deploy the application

Expected behavior

The image updater should preserve the existing global.image.tag value when:

• forceUpdate: true is set
• The global.image.tag is explicitly set in the Application manifest as a Helm parameter

The image updater should not remove Helm parameters from the Application manifest, and should not set global.image.tag to empty, which results in invalid image references.

Additional context

• This issue only occurs when forceUpdate: true is set
• When forceUpdate: false (or omitted), the image updater works correctly and preserves the tag value
• This appears to be a regression from previous behavior where the tag value was preserved
• Related to the fix for issue Cannot use digest update strategy with forceUpdate: true without version constraint #1344
• The error occurs because Kubernetes/Docker cannot parse image references with empty tags (e.g., registry/image:)

Version

1.0.1

Logs

Failed to apply default image tag "example-registry/docker/frontend-partners:": couldn't parse image name "example-registry/docker/frontend-partners:": invalid reference format

[chengfang]

I agree that the original helm param should not be overwritten with empty value or removed. But the digest update strategy expects a tag when you specify the imageName. In your case, imageName: "example-registry/docker/frontend-partners" should be something like imageName: "example-registry/docker/frontend-partners:latest" for digest strategy to work properly.