homeassistant: strict values.schema.json and null-safe hardening

No ingress gate change: this chart already honours ingress.enabled, and
its ingress block keeps the upstream-style host/tls lists that the README
documents as an exception. The schema models that shape as it is instead
of pushing the repo's domain/clusterIssuer pair onto it, and the list
entries stay open because they go verbatim into the Ingress spec.

The domain checkpoint ran over values.yaml and templates and came back
empty: ingress.domain does not exist in this chart at all.

1. values.schema.json (#68): additionalProperties: false on every
   chart-owned object level. Pod-spec passthrough (volumes, volumeMounts,
   nodeSelector, tolerations, affinity, ingress hosts/tls) stays open.

2. Null-safety for hardening, probes and resources (#99).

   This chart's hardening is a documented deviation and the fallbacks
   reproduce it exactly: the pod context is deliberately EMPTY, because
   the official image must start as root (s6-overlay does its setup as
   uid 0 and the image has no non-root user), and capabilities.add keeps
   NET_RAW, without which device discovery (DHCP watcher, ping/arp
   integrations) logs "Operation not permitted".

core.storage stays deliberately not null-safe: an erased block yields an
invalid PVC, which is the loud class #99 excludes.

The #82 limitation around the 1Password-backed config Secret is
untouched: Helm never sees the content, so it cannot be hashed, and the
values.yaml note about the manual rollout restart stays as it is.

Rendering with normal values is byte-identical to 5.0.0.

homeassistant/templates/_helpers.tpl

@@ -114,3 +114,165 @@ template-chart is the reference implementation.
 1
 {{- end -}}
 {{- end -}}
+
+{{/*
+Merge a user-supplied values sub-tree onto a dict of chart defaults so that a
+null / empty override falls back to the defaults instead of erasing them.
+
+Input: dict "defaults" <dict> "given" <dict|nil> "path" <string, optional
+values path used in error messages>. Output: YAML of the merged dict (consume
+it with fromYaml).
+
+Why this exists (issue #99): Helm merges values maps recursively, but an
+override key written without children — e.g. a leftover
+
+  securityContext:
+
+after deleting its last remaining sub-key — is YAML null. Where the chart
+defines a default, Helm treats that null as a deletion of the default; the
+template then renders "securityContext: null". The workload starts and reports
+healthy while being unhardened, so nothing points at the mistake. The same
+shape erases a probe (it disappears) or the resources block (no requests, no
+computed limits). This helper defines the opposite semantics: an empty block
+means "chart defaults apply".
+
+Rules:
+  - a nil "given" is treated as an empty dict (all defaults apply).
+  - a key whose override value is null keeps the default (nulls never delete).
+  - a key present in both as a map is merged recursively, so a partially
+    filled block only overrides the keys it actually sets.
+  - a scalar override for a key the defaults define as a map is rejected with
+    a message naming the values path, instead of failing later with a template
+    field error.
+  - any other set value wins as given, including an explicit false or 0 —
+    Helm's "default" and sprig's "mergeOverwrite" would both swallow those
+    zero values, hence the explicit kindIs "invalid" nil check.
+  - keys only present in the override are passed through unchanged.
+
+NOTE: like the helpers above, this is duplicated into every chart's
+templates/_helpers.tpl with the chart's name as define prefix, because charts
+in this repo deliberately have no dependencies.
+*/}}
+{{- define "homeassistant.defaultedDict" -}}
+{{- $defaults := .defaults | default dict -}}
+{{- $given := .given -}}
+{{- $path := .path | default "value" -}}
+{{- if kindIs "invalid" $given -}}
+{{- $given = dict -}}
+{{- end -}}
+{{- if not (kindIs "map" $given) -}}
+{{- fail (printf "%s must be a mapping or null, got %s (%v)" $path (kindOf $given) $given) -}}
+{{- end -}}
+{{- $out := deepCopy $defaults -}}
+{{- range $key, $value := $given -}}
+{{- if not (kindIs "invalid" $value) -}}
+{{- $default := index $defaults $key -}}
+{{- if and (kindIs "map" $value) (kindIs "map" $default) -}}
+{{- $_ := set $out $key (fromYaml (include "homeassistant.defaultedDict" (dict "defaults" $default "given" $value "path" (printf "%s.%s" $path $key)))) -}}
+{{- else if kindIs "map" $default -}}
+{{- fail (printf "%s.%s must be a mapping or null, got %s (%v)" $path $key (kindOf $value) $value) -}}
+{{- else -}}
+{{- $_ := set $out $key $value -}}
+{{- end -}}
+{{- end -}}
+{{- end -}}
+{{- toYaml $out -}}
+{{- end -}}
+
+{{/*
+Pick one sub-block out of a values block that may itself be null.
+
+Input: dict "block" <dict|nil> "key" <string> "path" <string>.
+Returns YAML of dict "value" <the sub-block, may be nil>, after rejecting a
+non-mapping block with a message that names the values path. Needed because
+".Values.securityContext" can itself be erased.
+*/}}
+{{- define "homeassistant.subBlock" -}}
+{{- $block := .block -}}
+{{- if kindIs "invalid" $block -}}
+{{- $block = dict -}}
+{{- end -}}
+{{- if not (kindIs "map" $block) -}}
+{{- fail (printf "%s must be a mapping or null, got %s (%v)" .path (kindOf $block) $block) -}}
+{{- end -}}
+{{- toYaml (dict "value" (index $block .key)) -}}
+{{- end -}}
+
+{{/*
+The effective security contexts, probes and resources (issue #99).
+
+The defaults below MUST stay in sync with the corresponding blocks in
+values.yaml, which stays the documented, user-facing place for them; this copy
+is only the fallback for the case where an override has erased the block.
+
+Like several other charts here, this one keeps replicas, resources, probes and
+securityContext at the TOP level of values.yaml, so the paths in the error
+messages have no chart-name prefix.
+
+IMPORTANT - this chart's hardening is a DOCUMENTED DEVIATION and the fallbacks
+reproduce it exactly rather than restoring the repo standard:
+
+  - The pod context is deliberately EMPTY: the official Home Assistant
+    container must start as root (s6-overlay performs its setup as uid 0 and
+    the image supports no non-root user), so runAsNonRoot / runAsUser are not
+    set.
+  - capabilities.add keeps NET_RAW: Home Assistant's device discovery (DHCP
+    watcher, ping/arp integrations) uses raw sockets and logs "Operation not
+    permitted" without it.
+
+The probes address the container port by its name ("http").
+*/}}
+{{- define "homeassistant.podSecurityContext" -}}
+{{- $given := (fromYaml (include "homeassistant.subBlock" (dict "block" . "key" "pod" "path" "securityContext"))).value -}}
+{{- $defaults := dict -}}
+{{- include "homeassistant.defaultedDict" (dict "defaults" $defaults "given" $given "path" "securityContext.pod") -}}
+{{- end -}}
+
+{{- define "homeassistant.containerSecurityContext" -}}
+{{- $given := (fromYaml (include "homeassistant.subBlock" (dict "block" . "key" "container" "path" "securityContext"))).value -}}
+{{- $defaults := dict
+      "allowPrivilegeEscalation" false
+      "readOnlyRootFilesystem" true
+      "capabilities" (dict "drop" (list "ALL") "add" (list "NET_RAW")) -}}
+{{- include "homeassistant.defaultedDict" (dict "defaults" $defaults "given" $given "path" "securityContext.container") -}}
+{{- end -}}
+
+{{- define "homeassistant.livenessProbe" -}}
+{{- $defaults := dict
+      "httpGet" (dict "path" "/" "port" "http")
+      "periodSeconds" 10
+      "timeoutSeconds" 5
+      "failureThreshold" 3 -}}
+{{- include "homeassistant.defaultedDict" (dict "defaults" $defaults "given" . "path" "livenessProbe") -}}
+{{- end -}}
+
+{{- define "homeassistant.readinessProbe" -}}
+{{- $defaults := dict
+      "httpGet" (dict "path" "/" "port" "http")
+      "periodSeconds" 10
+      "timeoutSeconds" 5
+      "failureThreshold" 3 -}}
+{{- include "homeassistant.defaultedDict" (dict "defaults" $defaults "given" . "path" "readinessProbe") -}}
+{{- end -}}
+
+{{- define "homeassistant.startupProbe" -}}
+{{- $defaults := dict
+      "httpGet" (dict "path" "/" "port" "http")
+      "periodSeconds" 10
+      "timeoutSeconds" 5
+      "failureThreshold" 30 -}}
+{{- include "homeassistant.defaultedDict" (dict "defaults" $defaults "given" . "path" "startupProbe") -}}
+{{- end -}}
+
+{{/*
+The effective resources block, fed into the resources helper above so that an
+erased "resources:" still yields the chart's requests and computed limits
+instead of a container without any resource accounting.
+*/}}
+{{- define "homeassistant.effectiveResources" -}}
+{{- $defaults := dict
+      "limitFactor" 3
+      "requests" (dict "cpu" 0.2 "memory" "512Mi" "ephemeralStorage" "128Mi") -}}
+{{- $merged := fromYaml (include "homeassistant.defaultedDict" (dict "defaults" $defaults "given" . "path" "resources")) -}}
+{{- include "homeassistant.resources" $merged -}}
+{{- end -}}

homeassistant/templates/homeassistant.sfs.yaml

@@ -30,13 +30,13 @@ spec:
     spec:
       automountServiceAccountToken: false
       securityContext:
-        {{- toYaml .Values.securityContext.pod | nindent 8 }}
+        {{- include "homeassistant.podSecurityContext" .Values.securityContext | nindent 8 }}
       containers:
         - name: "{{ .Release.Name }}-{{ .Chart.Name }}"
           image: "ghcr.io/home-assistant/home-assistant:{{ .Chart.AppVersion }}"
           imagePullPolicy: IfNotPresent
           securityContext:
-            {{- toYaml .Values.securityContext.container | nindent 12 }}
+            {{- include "homeassistant.containerSecurityContext" .Values.securityContext | nindent 12 }}
           env:
             - name: TZ
               value: "{{ .Values.core.timezone }}"
@@ -65,13 +65,13 @@ spec:
               containerPort: 8123
               protocol: TCP
           livenessProbe:
-            {{- toYaml .Values.livenessProbe | nindent 12 }}
+            {{- include "homeassistant.livenessProbe" .Values.livenessProbe | nindent 12 }}
           readinessProbe:
-            {{- toYaml .Values.readinessProbe | nindent 12 }}
+            {{- include "homeassistant.readinessProbe" .Values.readinessProbe | nindent 12 }}
           startupProbe:
-            {{- toYaml .Values.startupProbe | nindent 12 }}
+            {{- include "homeassistant.startupProbe" .Values.startupProbe | nindent 12 }}
           resources:
-            {{- include "homeassistant.resources" .Values.resources | nindent 12 }}
+            {{- include "homeassistant.effectiveResources" .Values.resources | nindent 12 }}
           volumeMounts:
             - mountPath: /config/configuration.yaml
               subPath: configuration.yaml