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

When using the .repo.GetAppDetails function inside a notification template, the returned object has a nil Helm field for multi-source applications. This makes it impossible to reliably access Helm values (e.g. image.tag) via $appDetails.Helm.GetParameterValueByName in notification templates for multi-source apps.

The function always operates on app.spec.source (the single-source field), which is nil for multi-source applications, meaning the result never includes any Helm data regardless of how the sources are configured.

To Reproduce

1. Create a multi-source ArgoCD application with the following structure:

spec:
  sources:
    - repoURL: 'https://github.com/foo/bar-apps.git'
      targetRevision: HEAD
      ref: values
    - repoURL: 'registry.example.com/helm'
      chart: 'foo-default-chart'
      targetRevision: '1.2.3'
      helm:
        valueFiles:
          - '$values/clusters/env/cluster/shared.yaml'
          - '$values/applications/foo-app/shared.yaml'
          - '$values/applications/foo-app/env/cluster/values.yaml'

2. Create a notification template that calls .repo.GetAppDetails and checks $appDetails.Helm:

template.slack-on-deployed: |
  slack:
    blocks: |
      {{- $appDetails := (call .repo.GetAppDetails) }}
      {{- if and $appDetails $appDetails.Helm }}
        {{- $imageVersion = $appDetails.Helm.GetParameterValueByName "foo-default-chart.image.tag" }}
      {{- end }}

3. Trigger a sync on the multi-source application.
4. Observe that $appDetails.Helm is always nil, so $imageVersion is never populated from Helm parameters.

Expected behavior

(call .repo.GetAppDetails) should either:

• Accept a source index argument so callers can specify which source to inspect (e.g. (call .repo.GetAppDetails 1) for the second source), or
• Return aggregated Helm data across all sources when the application uses spec.sources

Currently there is no reliable way to retrieve Helm parameter values inside notification templates for multi-source applications.

Workarounds attempted

• Passing a source index: (call .repo.GetAppDetails 0) — causes a runtime error: wrong number of args for $.repo.GetAppDetails: got 1 want 0
• Falling back to app.status.summary.images — unreliable during canary rollouts where multiple image tags coexist across stable and canary pods
• Falling back to app.status.operationState.syncResult.resources[*].images — works but is fragile and depends on resource ordering and it is only useful to access image information, not other helm values

Version

argocd: v3.3.2
  BuildDate: 2026-02-22T12:33:55Z
  GitCommit: 8a3940d8db27928931f0a85ba7c636e54786bddc
  GitTreeState: clean
  GitTag: v3.3.2
  GoVersion: go1.25.5
  Compiler: gc
  Platform: linux/amd64