controller-tools: +kubebuilder:default={} does not use nested defaults

So I believe I exposed a bug in kubebuilder…

when I define a +kubebuilder:default={} as a pointer to another type with +kubebuilder:default values I assume those values should propagate to the parent object.

For example

// policyAuditConfig is the configuration for network policy audit events. If unset,
// reported defaults are used.
// +kubebuilder:default={}
// +optional
PolicyAuditConfig *PolicyAuditConfig `json:"policyAuditConfig,omitempty"`

Where the PolicyAuditConfig is defined in the same package

type PolicyAuditConfig struct {
	// rateLimit is the approximate maximum number of messages to generate per-second per-node. If
	// unset the default of 20 msg/sec is used.
	// +kubebuilder:default=20
	// +kubebuilder:validation:Minimum=1
	// +optional
	RateLimit *uint32 `json:"rateLimit,omitempty"`

	// maxFilesSize is the max size an ACL_audit log file is allowed to reach before rotation occurs
	// Units are in MB and the Default is 50MB
	// +kubebuilder:default=50
	// +kubebuilder:validation:Minimum=1
	// +optional
	MaxFileSize *uint32 `json:"maxFileSize,omitempty"`

	// destination is the location for policy log messages.
	// Regardless of this config, persistent logs will always be dumped to the host
	// at /var/log/ovn/ however
	// Additionally syslog output may be configured as follows.
	// Valid values are:
	// - "libc" -> to use the libc syslog() function of the host node's journdald process
	// - "udp:host:port" -> for sending syslog over UDP
	// - "unix:file" -> for using the UNIX domain socket directly
	// - "null" -> to discard all messages logged to syslog
	// The default is "null"
	// +kubebuilder:default=null
	// +kubebuilder:pattern='^libc$|^null$|^udp:(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]):([0-9]){0,5}$|^unix:(\/[^\/ ]*)+([^\/\s])$'
	// +optional
	Destination string `json:"destination,omitempty"`

	// syslogFacility the RFC5424 facility for generated messages, e.g. "kern". Default is "local0"
	// +kubebuilder:default=local0
	// +kubebuilder:Enum=kern;user;mail;daemon;auth;syslog;lpr;news;uucp;clock;ftp;ntp;audit;alert;clock2;local0;local1;local2;local3;local4;local5;local6;local7
	// +optional
	SyslogFacility string `json:"syslogFacility,omitempty"`
}

However rather than rendering the default correctly I see the following in the generated yaml

policyAuditConfig:
  description: policyAuditConfig is the configuration for network policy audit events. If unset, reported defaults are used.
  type: object
  default: null
  properties:
    destination:
      description: 'destination is the location for policy log messages. Regardless of this config, persistent logs will always be dumped to the host at /var/log/ovn/ however Additionally syslog output may be configured as follows. Valid values are: - "libc" -> to use the libc syslog() function of the host node''s journdald process - "udp:host:port" -> for sending syslog over UDP - "unix:file" -> for using the UNIX domain socket directly - "null" -> to discard all messages logged to syslog The default is "null"'
      type: string
      default: "null"
    maxFileSize:
      description: maxFilesSize is the max size an ACL_audit log file is allowed to reach before rotation occurs Units are in MB and the Default is 50MB
      type: integer
      format: int32
      default: 50
      minimum: 1
    rateLimit:
      description: rateLimit is the approximate maximum number of messages to generate per-second per-node. If unset the default of 20 msg/sec is used.
      type: integer
      format: int32
      default: 20
      minimum: 1
    syslogFacility:
      description: syslogFacility the RFC5424 facility for generated messages, e.g. "kern". Default is "local0"
      type: string
      default: local0

Specifically the default value is null where it should be populated automatically by the defined nested defaults.

I am happy to help propose a fix here, however after spending some time playing with the codebase I’m realizing I will probably need some assistance from someone more experienced with kubebuilder

I already reached out on slack and got no response, which prompted me to open this issue.

Thanks, Andrew