kyaml: initial support for yaml and resource manipulation

kyaml/yaml/walk/map.go

@@ -0,0 +1,81 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package walk
+
+import (
+	"sort"
+
+	"sigs.k8s.io/kustomize/kyaml/sets"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+// walkMap returns the value of VisitMap
+//
+// - call VisitMap
+// - set the return value on l.Dest
+// - walk each source field
+// - set each source field value on l.Dest
+func (l Walker) walkMap() (*yaml.RNode, error) {
+	// get the new map value
+	dest, err := l.Sources.setDestNode(l.VisitMap(l.Sources))
+	if dest == nil || err != nil {
+		return nil, err
+	}
+
+	// recursively set the field values on the map
+	for _, key := range l.fieldNames() {
+		val, err := Walker{Visitor: l,
+			Sources: l.fieldValue(key), Path: append(l.Path, key)}.Walk()
+		if err != nil {
+			return nil, err
+		}
+
+		// this handles empty and non-empty values
+		_, err = dest.Pipe(yaml.FieldSetter{Name: key, Value: val})
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return dest, nil
+}
+
+// valueIfPresent returns node.Value if node is non-nil, otherwise returns nil
+func (l Walker) valueIfPresent(node *yaml.MapNode) *yaml.RNode {
+	if node == nil {
+		return nil
+	}
+	return node.Value
+}
+
+// fieldNames returns a sorted slice containing the names of all fields that appear in any of
+// the sources
+func (l Walker) fieldNames() []string {
+	fields := sets.String{}
+	for _, s := range l.Sources {
+		if s == nil {
+			continue
+		}
+		// don't check error, we know this is a mapping node
+		sFields, _ := s.Fields()
+		fields.Insert(sFields...)
+	}
+	result := fields.List()
+	sort.Strings(result)
+	return result
+}
+
+// fieldValue returns a slice containing each source's value for fieldName
+func (l Walker) fieldValue(fieldName string) []*yaml.RNode {
+	var fields []*yaml.RNode
+	for i := range l.Sources {
+		if l.Sources[i] == nil {
+			fields = append(fields, nil)
+			continue
+		}
+		field := l.Sources[i].Field(fieldName)
+		fields = append(fields, l.valueIfPresent(field))
+	}
+	return fields
+}