kustomize transformers to create fields if they are null

api/filters/fsslice/fieldspec_filter.go

@@ -23,6 +23,8 @@ type fieldSpecFilter struct {
 	// CreateKind defines the type of node to create if the field is not found
 	CreateKind yaml.Kind
 
+	CreateTag string
+
 	// path keeps internal state about the current path
 	path []string
 }
@@ -63,6 +65,8 @@ func (fltr fieldSpecFilter) field(obj *yaml.RNode) error {
 
 	// lookup the field matching the next path element
 	var lookupField yaml.Filter
+	var kind yaml.Kind
+	var tag string
 	switch {
 	case !fltr.FieldSpec.CreateIfNotPresent || fltr.CreateKind == 0 || isSeq:
 		// dont' create the field if we don't find it
@@ -70,9 +74,13 @@ func (fltr fieldSpecFilter) field(obj *yaml.RNode) error {
 	case len(fltr.path) <= 1:
 		// create the field if it is missing: use the provided node kind
 		lookupField = yaml.LookupCreate(fltr.CreateKind, fieldName)
+		kind = fltr.CreateKind
+		tag = fltr.CreateTag
 	default:
 		// create the field if it is missing: must be a mapping node
 		lookupField = yaml.LookupCreate(yaml.MappingNode, fieldName)
+		kind = yaml.MappingNode
+		tag = "!!map"
 	}
 
 	// locate (or maybe create) the field
@@ -81,6 +89,13 @@ func (fltr fieldSpecFilter) field(obj *yaml.RNode) error {
 		return errors.WrapPrefixf(err, "fieldName: %s", fieldName)
 	}
 
+	// if the value exists, but is null, then change it to the creation type
+	// TODO: update yaml.LookupCreate to support this
+	if field.YNode().Tag == "!!null" {
+		field.YNode().Kind = kind
+		field.YNode().Tag = tag
+	}
+
 	// copy the current fltr and change the path on the copy
 	var next = fltr
 	// call filter for the next path element on the matching field

api/filters/fsslice/fsslice.go

@@ -49,6 +49,9 @@ type Filter struct {
 
 	// CreateKind is used to create fields that do not exist
 	CreateKind yaml.Kind
+
+	// CreateTag is used to set the tag if encountering a null field
+	CreateTag string
 }
 
 func (fltr Filter) Filter(obj *yaml.RNode) (*yaml.RNode, error) {
@@ -60,6 +63,7 @@ func (fltr Filter) Filter(obj *yaml.RNode) (*yaml.RNode, error) {
 			FieldSpec:  fltr.FsSlice[i],
 			SetValue:   fltr.SetValue,
 			CreateKind: fltr.CreateKind,
+			CreateTag:  fltr.CreateTag,
 		}).Filter(obj)
 		if err != nil {
 			return nil, err