teamspeak-server: strict values.schema.json and null-safe hardening

No ingress gate: this chart has no Ingress at all (voice/file-transfer
are exposed via NodePort), and ingress.domain appears neither in its
templates nor in its values.

1. values.schema.json (#68): additionalProperties: false on every
   chart-owned object level. Note that this chart keeps replicas,
   resources, probes and securityContext at the TOP level rather than
   under a chart-named key, so the schema mirrors that shape.

2. Null-safety for hardening, probes and resources (#99). The rebuilt
   probes keep the "file-transfer" port name: the voice service is UDP
   and cannot be probed, so that TCP port is the only thing a probe can
   target - a default probe without it would leave the workload with no
   working probe at all.

   The container defaults keep capabilities.add as an empty list, exactly
   as values.yaml has it, so an erased block restores today's rendering
   byte for byte rather than a cleaned-up variant.

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

Rendering with normal values is byte-identical to 4.0.0.

teamspeak-server/templates/_helpers.tpl

@@ -114,3 +114,162 @@ 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": no readOnlyRootFilesystem, no
+dropped capabilities, no allowPrivilegeEscalation: false. 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 "teamspeak-server.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 "teamspeak-server.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 "teamspeak-server.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.
+
+Note that this chart keeps these blocks at the TOP level of values.yaml, not
+under a chart-named key, so the paths in the error messages have no prefix.
+
+The probes address the TCP file-transfer port by its name ("file-transfer"),
+because the voice service is UDP and cannot be probed. A rebuilt default probe
+must keep that port name, otherwise the workload has no working probe at all.
+*/}}
+{{- define "teamspeak-server.podSecurityContext" -}}
+{{- $given := (fromYaml (include "teamspeak-server.subBlock" (dict "block" . "key" "pod" "path" "securityContext"))).value -}}
+{{- $defaults := dict
+      "runAsNonRoot" true
+      "runAsUser" 9987
+      "runAsGroup" 9987
+      "fsGroup" 9987
+      "fsGroupChangePolicy" "Always" -}}
+{{- include "teamspeak-server.defaultedDict" (dict "defaults" $defaults "given" $given "path" "securityContext.pod") -}}
+{{- end -}}
+
+{{- define "teamspeak-server.containerSecurityContext" -}}
+{{- $given := (fromYaml (include "teamspeak-server.subBlock" (dict "block" . "key" "container" "path" "securityContext"))).value -}}
+{{- $defaults := dict
+      "allowPrivilegeEscalation" false
+      "readOnlyRootFilesystem" true
+      "runAsNonRoot" true
+      "capabilities" (dict "drop" (list "ALL") "add" (list)) -}}
+{{- include "teamspeak-server.defaultedDict" (dict "defaults" $defaults "given" $given "path" "securityContext.container") -}}
+{{- end -}}
+
+{{- define "teamspeak-server.livenessProbe" -}}
+{{- $defaults := dict
+      "tcpSocket" (dict "port" "file-transfer")
+      "periodSeconds" 10
+      "timeoutSeconds" 5
+      "failureThreshold" 3 -}}
+{{- include "teamspeak-server.defaultedDict" (dict "defaults" $defaults "given" . "path" "livenessProbe") -}}
+{{- end -}}
+
+{{- define "teamspeak-server.readinessProbe" -}}
+{{- $defaults := dict
+      "tcpSocket" (dict "port" "file-transfer")
+      "periodSeconds" 10
+      "timeoutSeconds" 5
+      "failureThreshold" 3 -}}
+{{- include "teamspeak-server.defaultedDict" (dict "defaults" $defaults "given" . "path" "readinessProbe") -}}
+{{- end -}}
+
+{{- define "teamspeak-server.startupProbe" -}}
+{{- $defaults := dict
+      "tcpSocket" (dict "port" "file-transfer")
+      "periodSeconds" 5
+      "timeoutSeconds" 5
+      "failureThreshold" 30 -}}
+{{- include "teamspeak-server.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 "teamspeak-server.effectiveResources" -}}
+{{- $defaults := dict
+      "limitFactor" 3
+      "requests" (dict "cpu" 0.2 "memory" "100Mi" "ephemeral-storage" "100Mi") -}}
+{{- $merged := fromYaml (include "teamspeak-server.defaultedDict" (dict "defaults" $defaults "given" . "path" "resources")) -}}
+{{- include "teamspeak-server.resources" $merged -}}
+{{- end -}}

teamspeak-server/templates/teamspeak-server.sfs.yaml

@@ -17,7 +17,7 @@ spec:
     spec:
       automountServiceAccountToken: false
       securityContext:
-        {{- toYaml .Values.securityContext.pod | nindent 8 }}
+        {{- include "teamspeak-server.podSecurityContext" .Values.securityContext | nindent 8 }}
       containers:
         - name: {{ .Release.Name }}-{{ .Chart.Name }}-sfs
           image: "teamspeaksystems/teamspeak6-server:{{ .Chart.AppVersion }}"
@@ -60,15 +60,15 @@ spec:
             {{- end }}
             {{- end }}
           livenessProbe:
-            {{- toYaml .Values.livenessProbe | nindent 12 }}
+            {{- include "teamspeak-server.livenessProbe" .Values.livenessProbe | nindent 12 }}
           readinessProbe:
-            {{- toYaml .Values.readinessProbe | nindent 12 }}
+            {{- include "teamspeak-server.readinessProbe" .Values.readinessProbe | nindent 12 }}
           startupProbe:
-            {{- toYaml .Values.startupProbe | nindent 12 }}
+            {{- include "teamspeak-server.startupProbe" .Values.startupProbe | nindent 12 }}
           resources:
-            {{- include "teamspeak-server.resources" .Values.resources | nindent 12 }}
+            {{- include "teamspeak-server.effectiveResources" .Values.resources | nindent 12 }}
           securityContext:
-            {{- toYaml .Values.securityContext.container | nindent 12 }}
+            {{- include "teamspeak-server.containerSecurityContext" .Values.securityContext | nindent 12 }}
           volumeMounts:
             - name: "teamspeak-volume"
               mountPath: /var/tsserver/