Add strict values.schema.json and null-safe hardening to urlaubsverwaltung

Two changes, both about values that do not do what they promise:

1. values.schema.json (#68): additionalProperties: false on every
   chart-owned object level, so a key the chart does not read is rejected
   at render time instead of being silently ignored.

2. Null-safety for hardening, probes and resources (#99): an override
   written without children is YAML null and replaced the whole default
   sub-tree, rendering "securityContext: null" (unhardened container), a
   vanished probe or a container without resource accounting - silently.
   The defaultedDict helper from #96 is adopted so an empty block means
   "chart defaults apply", while an explicitly set value still wins,
   including false and 0.

The schema types allow null for exactly these blocks, so the two changes
agree instead of the schema rejecting what the helper is meant to absorb.

No ingress gate here: this chart already gates its Ingress correctly.

Rendering with normal values is byte-identical to the previous version.

Major bump: a schema can break existing deployments that carry dead keys.

urlaubsverwaltung/templates/_helpers.tpl

@@ -114,3 +114,157 @@ 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 and replaces the
+whole default sub-tree. The container then renders with "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 "urlaubsverwaltung.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 "urlaubsverwaltung.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.<app>.securityContext" can itself be erased, and indexing into nil
+inside a template is not an error but silently yields nothing.
+*/}}
+{{- define "urlaubsverwaltung.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 pod / container 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.
+*/}}
+{{- define "urlaubsverwaltung.podSecurityContext" -}}
+{{- $given := (fromYaml (include "urlaubsverwaltung.subBlock" (dict "block" . "key" "pod" "path" "urlaubsverwaltung.securityContext"))).value -}}
+{{- $defaults := dict
+      "runAsNonRoot" true
+      "runAsUser" 1002
+      "runAsGroup" 1001 -}}
+{{- include "urlaubsverwaltung.defaultedDict" (dict "defaults" $defaults "given" $given "path" "urlaubsverwaltung.securityContext.pod") -}}
+{{- end -}}
+
+{{- define "urlaubsverwaltung.containerSecurityContext" -}}
+{{- $given := (fromYaml (include "urlaubsverwaltung.subBlock" (dict "block" . "key" "container" "path" "urlaubsverwaltung.securityContext"))).value -}}
+{{- $defaults := dict
+      "allowPrivilegeEscalation" false
+      "readOnlyRootFilesystem" true
+      "runAsNonRoot" true
+      "capabilities" (dict "drop" (list "ALL")) -}}
+{{- include "urlaubsverwaltung.defaultedDict" (dict "defaults" $defaults "given" $given "path" "urlaubsverwaltung.securityContext.container") -}}
+{{- end -}}
+
+{{- define "urlaubsverwaltung.livenessProbe" -}}
+{{- $defaults := dict
+      "httpGet" (dict "port" 8080 "path" "/actuator/health/liveness")
+      "periodSeconds" 10
+      "failureThreshold" 3
+      "successThreshold" 1
+      "timeoutSeconds" 5 -}}
+{{- include "urlaubsverwaltung.defaultedDict" (dict "defaults" $defaults "given" . "path" "urlaubsverwaltung.livenessProbe") -}}
+{{- end -}}
+
+{{- define "urlaubsverwaltung.readinessProbe" -}}
+{{- $defaults := dict
+      "httpGet" (dict "port" 8080 "path" "/actuator/health/readiness")
+      "periodSeconds" 5
+      "failureThreshold" 3
+      "successThreshold" 1
+      "timeoutSeconds" 5 -}}
+{{- include "urlaubsverwaltung.defaultedDict" (dict "defaults" $defaults "given" . "path" "urlaubsverwaltung.readinessProbe") -}}
+{{- end -}}
+
+{{- define "urlaubsverwaltung.startupProbe" -}}
+{{- $defaults := dict
+      "httpGet" (dict "port" 8080 "path" "/actuator/health/liveness")
+      "periodSeconds" 10
+      "failureThreshold" 30
+      "timeoutSeconds" 5 -}}
+{{- include "urlaubsverwaltung.defaultedDict" (dict "defaults" $defaults "given" . "path" "urlaubsverwaltung.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 "urlaubsverwaltung.effectiveResources" -}}
+{{- $defaults := dict
+      "limitFactor" 3
+      "requests" (dict "cpu" 0.1 "memory" "768Mi" "ephemeralStorage" "10Mi") -}}
+{{- $merged := fromYaml (include "urlaubsverwaltung.defaultedDict" (dict "defaults" $defaults "given" . "path" "urlaubsverwaltung.resources")) -}}
+{{- include "urlaubsverwaltung.resources" $merged -}}
+{{- end -}}

urlaubsverwaltung/templates/urlaubsverwaltung.deployment.yaml

@@ -17,13 +17,13 @@ spec:
     spec:
       automountServiceAccountToken: false
       securityContext:
-        {{- toYaml .Values.urlaubsverwaltung.securityContext.pod | nindent 8 }}
+        {{- include "urlaubsverwaltung.podSecurityContext" .Values.urlaubsverwaltung.securityContext | nindent 8 }}
       containers:
         - name: {{ .Release.Name }}-{{ .Chart.Name }}-deployment
           image: "urlaubsverwaltung/urlaubsverwaltung:{{ .Chart.AppVersion }}"
           imagePullPolicy: IfNotPresent
           securityContext:
-            {{- toYaml .Values.urlaubsverwaltung.securityContext.container | nindent 12 }}
+            {{- include "urlaubsverwaltung.containerSecurityContext" .Values.urlaubsverwaltung.securityContext | nindent 12 }}
           volumeMounts:
             # The JVM (Tomcat work dir, temp files) needs a writable /tmp with
             # a read-only root filesystem.
@@ -130,13 +130,13 @@ spec:
             {{- end }}
             {{- end }}
           resources:
-            {{- include "urlaubsverwaltung.resources" .Values.urlaubsverwaltung.resources | nindent 12 }}
+            {{- include "urlaubsverwaltung.effectiveResources" .Values.urlaubsverwaltung.resources | nindent 12 }}
           livenessProbe:
-            {{- toYaml .Values.urlaubsverwaltung.livenessProbe | nindent 12 }}
+            {{- include "urlaubsverwaltung.livenessProbe" .Values.urlaubsverwaltung.livenessProbe | nindent 12 }}
           readinessProbe:
-            {{- toYaml .Values.urlaubsverwaltung.readinessProbe | nindent 12 }}
+            {{- include "urlaubsverwaltung.readinessProbe" .Values.urlaubsverwaltung.readinessProbe | nindent 12 }}
           startupProbe:
-            {{- toYaml .Values.urlaubsverwaltung.startupProbe | nindent 12 }}
+            {{- include "urlaubsverwaltung.startupProbe" .Values.urlaubsverwaltung.startupProbe | nindent 12 }}
       volumes:
         - name: tmp
           emptyDir: {}