adds MergePodTemplateSpecs that merges podTemplateSpecs (#2770)

merge podtemplatespecs

Signed-off-by: Chris Burns <[email protected]>

Author: ChrisJBurns

cmd/thv-operator/pkg/registryapi/podtemplatespec.go

@@ -270,6 +270,290 @@ func DefaultRegistryAPIPodTemplateSpec(labels map[string]string, configHash stri
 	).Build()
 }
 
+// MergePodTemplateSpecs merges a default PodTemplateSpec with a user-provided one.
+// User-provided values take precedence over defaults. This allows users to customize
+// infrastructure concerns while ensuring sensible defaults are applied where values
+// are not specified.
+//
+// The merge strategy starts with the user's PodTemplateSpec and fills in defaults
+// only where the user hasn't specified values. This means any field the user sets
+// (affinity, tolerations, nodeSelector, etc.) is automatically preserved.
+//
+// Merge behavior:
+//   - Labels/Annotations: Merged, with defaults added for missing keys
+//   - ServiceAccountName: Default only if user hasn't specified
+//   - Containers: Merged by name - defaults fill in missing container fields
+//   - Volumes: Merged by name - defaults added only if not present
+//   - All other PodSpec fields: User values preserved as-is
+func MergePodTemplateSpecs(defaultPTS, userPTS *corev1.PodTemplateSpec) corev1.PodTemplateSpec {
+	if userPTS == nil {
+		if defaultPTS == nil {
+			return corev1.PodTemplateSpec{}
+		}
+		return *defaultPTS.DeepCopy()
+	}
+
+	if defaultPTS == nil {
+		return *userPTS.DeepCopy()
+	}
+
+	// Start with a deep copy of the user's spec - this preserves all user fields automatically
+	result := userPTS.DeepCopy()
+
+	// Merge labels: add default labels that user hasn't specified
+	result.Labels = mergeStringMapsDefaultsFirst(defaultPTS.Labels, result.Labels)
+
+	// Merge annotations: add default annotations that user hasn't specified
+	result.Annotations = mergeStringMapsDefaultsFirst(defaultPTS.Annotations, result.Annotations)
+
+	// Set service account only if user hasn't specified one
+	if result.Spec.ServiceAccountName == "" {
+		result.Spec.ServiceAccountName = defaultPTS.Spec.ServiceAccountName
+	}
+
+	// Merge containers: user containers take precedence, defaults fill gaps
+	result.Spec.Containers = mergeContainersUserFirst(defaultPTS.Spec.Containers, result.Spec.Containers)
+
+	// Merge init containers
+	result.Spec.InitContainers = mergeContainersUserFirst(defaultPTS.Spec.InitContainers, result.Spec.InitContainers)
+
+	// Merge volumes: add default volumes that user hasn't specified
+	result.Spec.Volumes = mergeVolumesUserFirst(defaultPTS.Spec.Volumes, result.Spec.Volumes)
+
+	return *result
+}
+
+// mergeContainersUserFirst merges containers where user containers take precedence.
+// User containers are preserved, and default container fields fill in gaps.
+func mergeContainersUserFirst(defaults, user []corev1.Container) []corev1.Container {
+	if len(user) == 0 {
+		return defaults
+	}
+	if len(defaults) == 0 {
+		return user
+	}
+
+	// Create a map of default containers by name
+	defaultMap := make(map[string]corev1.Container)
+	for _, c := range defaults {
+		defaultMap[c.Name] = c
+	}
+
+	// Start with user containers, filling in defaults where needed
+	result := make([]corev1.Container, 0, len(user)+len(defaults))
+	merged := make(map[string]bool)
+
+	for _, userContainer := range user {
+		if defaultContainer, exists := defaultMap[userContainer.Name]; exists {
+			// Merge: user values take precedence, defaults fill gaps
+			result = append(result, mergeContainer(defaultContainer, userContainer))
+			merged[userContainer.Name] = true
+		} else {
+			// User container with no default - keep as-is
+			result = append(result, userContainer)
+		}
+	}
+
+	// Add default containers that user didn't specify
+	for _, defaultContainer := range defaults {
+		if !merged[defaultContainer.Name] {
+			result = append(result, defaultContainer)
+		}
+	}
+
+	return result
+}
+
+// mergeContainer merges a default container with a user container.
+// User values take precedence; defaults fill in where user hasn't specified.
+func mergeContainer(defaultContainer, userContainer corev1.Container) corev1.Container {
+	// Start with user container - preserves all user-specified fields
+	result := userContainer
+
+	// Fill in defaults only where user hasn't specified
+	if result.Image == "" {
+		result.Image = defaultContainer.Image
+	}
+	if len(result.Command) == 0 {
+		result.Command = defaultContainer.Command
+	}
+	if len(result.Args) == 0 {
+		result.Args = defaultContainer.Args
+	}
+	if result.WorkingDir == "" {
+		result.WorkingDir = defaultContainer.WorkingDir
+	}
+	if isResourcesEmpty(result.Resources) {
+		result.Resources = defaultContainer.Resources
+	}
+	if result.LivenessProbe == nil {
+		result.LivenessProbe = defaultContainer.LivenessProbe
+	}
+	if result.ReadinessProbe == nil {
+		result.ReadinessProbe = defaultContainer.ReadinessProbe
+	}
+	if result.StartupProbe == nil {
+		result.StartupProbe = defaultContainer.StartupProbe
+	}
+	if result.SecurityContext == nil {
+		result.SecurityContext = defaultContainer.SecurityContext
+	}
+	if result.ImagePullPolicy == "" {
+		result.ImagePullPolicy = defaultContainer.ImagePullPolicy
+	}
+
+	// Merge slices: add defaults that user hasn't specified
+	result.Ports = mergePortsUserFirst(defaultContainer.Ports, result.Ports)
+	result.Env = mergeEnvVarsUserFirst(defaultContainer.Env, result.Env)
+	result.VolumeMounts = mergeVolumeMountsUserFirst(defaultContainer.VolumeMounts, result.VolumeMounts)
+
+	return result
+}
+
+// mergeVolumesUserFirst merges volumes where user volumes take precedence.
+func mergeVolumesUserFirst(defaults, user []corev1.Volume) []corev1.Volume {
+	if len(user) == 0 {
+		return defaults
+	}
+	if len(defaults) == 0 {
+		return user
+	}
+
+	// Create a map of user volumes by name
+	userMap := make(map[string]bool)
+	for _, v := range user {
+		userMap[v.Name] = true
+	}
+
+	// Start with user volumes
+	result := make([]corev1.Volume, 0, len(user)+len(defaults))
+	result = append(result, user...)
+
+	// Add default volumes that user hasn't specified
+	for _, defaultVolume := range defaults {
+		if !userMap[defaultVolume.Name] {
+			result = append(result, defaultVolume)
+		}
+	}
+
+	return result
+}
+
+// mergePortsUserFirst merges ports where user ports take precedence.
+func mergePortsUserFirst(defaults, user []corev1.ContainerPort) []corev1.ContainerPort {
+	if len(user) == 0 {
+		return defaults
+	}
+	if len(defaults) == 0 {
+		return user
+	}
+
+	// Track user ports by name and port number
+	userByName := make(map[string]bool)
+	userByPort := make(map[int32]bool)
+	for _, p := range user {
+		if p.Name != "" {
+			userByName[p.Name] = true
+		}
+		userByPort[p.ContainerPort] = true
+	}
+
+	// Start with user ports
+	result := make([]corev1.ContainerPort, 0, len(user)+len(defaults))
+	result = append(result, user...)
+
+	// Add default ports that user hasn't specified
+	for _, defaultPort := range defaults {
+		nameConflict := defaultPort.Name != "" && userByName[defaultPort.Name]
+		portConflict := userByPort[defaultPort.ContainerPort]
+		if !nameConflict && !portConflict {
+			result = append(result, defaultPort)
+		}
+	}
+
+	return result
+}
+
+// mergeEnvVarsUserFirst merges env vars where user env vars take precedence.
+func mergeEnvVarsUserFirst(defaults, user []corev1.EnvVar) []corev1.EnvVar {
+	if len(user) == 0 {
+		return defaults
+	}
+	if len(defaults) == 0 {
+		return user
+	}
+
+	// Create a map of user env vars by name
+	userMap := make(map[string]bool)
+	for _, e := range user {
+		userMap[e.Name] = true
+	}
+
+	// Start with user env vars
+	result := make([]corev1.EnvVar, 0, len(user)+len(defaults))
+	result = append(result, user...)
+
+	// Add default env vars that user hasn't specified
+	for _, defaultEnv := range defaults {
+		if !userMap[defaultEnv.Name] {
+			result = append(result, defaultEnv)
+		}
+	}
+
+	return result
+}
+
+// mergeVolumeMountsUserFirst merges volume mounts where user mounts take precedence.
+func mergeVolumeMountsUserFirst(defaults, user []corev1.VolumeMount) []corev1.VolumeMount {
+	if len(user) == 0 {
+		return defaults
+	}
+	if len(defaults) == 0 {
+		return user
+	}
+
+	// Create a map of user volume mounts by name
+	userMap := make(map[string]bool)
+	for _, m := range user {
+		userMap[m.Name] = true
+	}
+
+	// Start with user mounts
+	result := make([]corev1.VolumeMount, 0, len(user)+len(defaults))
+	result = append(result, user...)
+
+	// Add default mounts that user hasn't specified
+	for _, defaultMount := range defaults {
+		if !userMap[defaultMount.Name] {
+			result = append(result, defaultMount)
+		}
+	}
+
+	return result
+}
+
+// mergeStringMapsDefaultsFirst merges string maps where user values override defaults.
+// Returns a map with all default keys, plus any additional user keys, with user values taking precedence.
+func mergeStringMapsDefaultsFirst(defaults, user map[string]string) map[string]string {
+	if len(defaults) == 0 && len(user) == 0 {
+		return nil
+	}
+
+	result := make(map[string]string)
+	for k, v := range defaults {
+		result[k] = v
+	}
+	for k, v := range user {
+		result[k] = v // User values override defaults
+	}
+	return result
+}
+
+// isResourcesEmpty checks if ResourceRequirements are empty.
+func isResourcesEmpty(resources corev1.ResourceRequirements) bool {
+	return len(resources.Requests) == 0 && len(resources.Limits) == 0
+}
+
 // findContainerByName finds a container by name in a slice of containers.
 // Returns a pointer to the container if found, nil otherwise.
 func findContainerByName(containers []corev1.Container, name string) *corev1.Container {