fix: remove tpl function causing template rendering error

[jerry-shao]

Description

Fix template rendering error in OpenTelemetry Demo chart caused by tpl function compatibility issues with newer Helm versions.

Problem

The chart was failing to deploy with the following error:

➜  ~ helm install my-otel-demo open-telemetry/opentelemetry-demo

Error: INSTALLATION FAILED: template: opentelemetry-demo/templates/component.yaml:12:12: executing "opentelemetry-demo/templates/component.yaml" at <include "otel-demo.deployment" $config>: error calling include: template: opentelemetry-demo/templates/_objects.tpl:109:16: executing "otel-demo.deployment" at <include "otel-demo.pod.env" .>: error calling include: template: opentelemetry-demo/templates/_pod.tpl:43:4: executing "otel-demo.pod.env" at <tpl (toYaml $allEnvs) .>: error calling tpl: cannot retrieve Template.Basepath from values inside tpl function: - name: OTEL_SERVICE_NAME
  valueFrom:
    fieldRef:
      apiVersion: v1
      fieldPath: metadata.labels['app.kubernetes.io/component']
- name: OTEL_COLLECTOR_NAME
  value: otel-collector
- name: OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE
  value: cumulative
- name: FLAGD_METRICS_EXPORTER
  value: otel
- name: OTEL_EXPORTER_OTLP_ENDPOINT
  value: http://$(OTEL_COLLECTOR_NAME):4318
- name: FLAGD_UI_PORT
  value: "4000"
- name: SECRET_KEY_BASE
  value: yYrECL4qbNwleYInGJYvVnSkwJuSQJ4ijPTx5tirGUXrbznFIBFVJdPl5t6O9ASw
- name: PHX_HOST
  value: localhost
- name: OTEL_RESOURCE_ATTRIBUTES
  value: service.name=$(OTEL_SERVICE_NAME),service.namespace=opentelemetry-demo,service.version={{
    .Chart.AppVersion }}: "BasePath" is not a value

Root Cause

The tpl function in _pod.tpl was attempting to re-process already-rendered YAML content as a template, which triggered Helm's restriction on accessing Template.Basepath within tpl functions in newer versions.

Solution

Replaced {{- tpl (toYaml $allEnvs) . }} with {{- toYaml $allEnvs }} in the pod environment template helper.

Changes

• File: charts/opentelemetry-demo/templates/_pod.tpl
• Change: Remove unnecessary tpl wrapper around toYaml output
• Impact: Maintains identical functionality while fixing Helm compatibility

Testing

• Chart deploys successfully with local changes
• All demo services accessible via frontend proxy
• No regression in generated YAML output

Type of Change

• Bug fix (non-breaking change which fixes an issue)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: jerry-shao / name: Mingjie Shao (a87d1f7)

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[TylerHelmuth]

I'm no sure removing the tpl call is the way we want to solve this as it'll remove the ability to define env vars with a template. I dont believe tpl is called anywhere higher in this function. What version of helm are you running?

[jerry-shao]

Problematic version:

> helm version
version.BuildInfo{Version:"v3.13.2", GitCommit:"2a2fb3b98829f1e0be6fb18af2f6599e0f4e8243", GitTreeState:"clean", GoVersion:"go1.21.4"}

Working versions:

> helm version
version.BuildInfo{Version:"v4.1.0", GitCommit:"4553a0a96e5205595079b6757236cc6f969ed1b9", GitTreeState:"clean", GoVersion:"go1.25.6", KubeClientVersion:"v1.35"}

[TylerHelmuth]

Are you able to point to a breaking change in helm 4 that is causing the chart not to work on 4.1?

[TylerHelmuth]

Additionally, can you confirm the behavior of otel-demo.pod.env with tpl removed? I assume it no longer handles rendering templated env var inputs. That is a feature we need to continue to support

[jerry-shao]

Hi @TylerHelmuth

helm 3.13.2 is the problematic version, the newer version 4.1.0 doesn't have this problem.