How can I prevent Helm charts from rendering an empty image tag in Argo CD deployments?

Below are some recommendations to avoid rendering an empty image tag and to align with best practices when integrating Helm charts with Argo CD:

1. Enforce a Valid Image Tag in the Template

Even though you already have a default (.Chart.AppVersion), an empty string in your values file still “overrides” the default. To prevent this, you can use the Helm required helper so that the template fails if the tag is not provided. For example:

YAMLCopied
image: "{{ .Values.image.registry }}/{{ .Values.image.repository }}:{{ required "Image tag must be provided" (cond (eq .Values.image.tag "") .Chart.AppVersion .Values.image.tag) }}"

In this snippet, if .Values.image.tag is empty, it falls back to .Chart.AppVersion. Adjust the logic as needed if you want to force a non-empty value.

2. Adjust the Values File

If you prefer not to use a fallback in the template, you can modify your values.yaml so it does not define an empty tag:

YAMLCopied
image:
  registry: registry.core.example.com
  repository: app-rest-api-ui
  pullPolicy: IfNotPresent
  # Remove the empty tag entry so that `.Chart.AppVersion` is used automatically

This way, the template default (.Chart.AppVersion) will be used without ambiguity.

3. Enforce a Required Tag

Another approach is to force users to specify the tag if they do not want to rely on a fallback. Using the required function as shown above is a good practice because it causes a clear failure (with an error message) during rendering rather than deploying an ambiguous or incorrect image.

4. Best Practices for Handling Image Tags in Helm with Argo CD

• Immutability: Always try to deploy images with immutable tags (or commit SHAs) to ensure that deployments are consistent and repeatable.
• Explicitness: Avoid defaults that might be unintentionally overridden by an empty value. Be explicit in your values file or use Helm functions to enforce required values.
• Validation: Utilize Helm template functions such as required to validate critical parameters like image tags to avoid unexpected rendering outcomes.
• Versioning Strategy: Consider using Git tags or commit SHAs (as mentioned in Argo CD best practices) when pointing to external repositories or upstream charts, ensuring that the actual content deployed does not change unexpectedly.

By following these practices, you help ensure that only the intended, valid image is deployed and reported by Argo CD while maintaining consistency across your environments.