update modules kustomize add helm

Signed-off-by: LiHui <andrewli@yunify.com>

vendor/sigs.k8s.io/kustomize/kyaml/yaml/fns.go

@@ -0,0 +1,769 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package yaml
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/davecgh/go-spew/spew"
+	"gopkg.in/yaml.v3"
+	"sigs.k8s.io/kustomize/kyaml/errors"
+)
+
+// Append creates an ElementAppender
+func Append(elements ...*yaml.Node) ElementAppender {
+	return ElementAppender{Elements: elements}
+}
+
+// ElementAppender adds all element to a SequenceNode's Content.
+// Returns Elements[0] if len(Elements) == 1, otherwise returns nil.
+type ElementAppender struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Elem is the value to append.
+	Elements []*yaml.Node `yaml:"elements,omitempty"`
+}
+
+func (a ElementAppender) Filter(rn *RNode) (*RNode, error) {
+	if err := ErrorIfInvalid(rn, yaml.SequenceNode); err != nil {
+		return nil, err
+	}
+	for i := range a.Elements {
+		rn.YNode().Content = append(rn.Content(), a.Elements[i])
+	}
+	if len(a.Elements) == 1 {
+		return NewRNode(a.Elements[0]), nil
+	}
+	return nil, nil
+}
+
+// ElementSetter sets the value for an Element in an associative list.
+// ElementSetter will append, replace or delete an element in an associative list.
+// To append, user a key-value pair that doesn't exist in the sequence. this
+// behavior is intended to handle the case that not matching element found. It's
+// not designed for this purpose. To append an element, please use ElementAppender.
+// To replace, set the key-value pair and a non-nil Element.
+// To delete, set the key-value pair and leave the Element as nil.
+// Every key must have a corresponding value.
+type ElementSetter struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Element is the new value to set -- remove the existing element if nil
+	Element *Node
+
+	// Key is a list of fields on the elements. It is used to find matching elements to
+	// update / delete
+	Keys []string
+
+	// Value is a list of field values on the elements corresponding to the keys. It is
+	// used to find matching elements to update / delete.
+	Values []string
+}
+
+// isMappingNode returns whether node is a mapping node
+func (e ElementSetter) isMappingNode(node *RNode) bool {
+	return ErrorIfInvalid(node, yaml.MappingNode) == nil
+}
+
+// isMappingSetter returns is this setter intended to set a mapping node
+func (e ElementSetter) isMappingSetter() bool {
+	return len(e.Keys) > 0 && e.Keys[0] != "" &&
+		len(e.Values) > 0 && e.Values[0] != ""
+}
+
+func (e ElementSetter) Filter(rn *RNode) (*RNode, error) {
+	if len(e.Keys) == 0 {
+		e.Keys = append(e.Keys, "")
+	}
+
+	if err := ErrorIfInvalid(rn, SequenceNode); err != nil {
+		return nil, err
+	}
+
+	// build the new Content slice
+	var newContent []*yaml.Node
+	matchingElementFound := false
+	for i := range rn.YNode().Content {
+		elem := rn.Content()[i]
+		newNode := NewRNode(elem)
+
+		// empty elements are not valid -- they at least need an associative key
+		if IsMissingOrNull(newNode) || IsEmptyMap(newNode) {
+			continue
+		}
+		// keep non-mapping node in the Content when we want to match a mapping.
+		if !e.isMappingNode(newNode) && e.isMappingSetter() {
+			newContent = append(newContent, elem)
+			continue
+		}
+
+		// check if this is the element we are matching
+		var val *RNode
+		var err error
+		found := true
+		for j := range e.Keys {
+			if j < len(e.Values) {
+				val, err = newNode.Pipe(FieldMatcher{Name: e.Keys[j], StringValue: e.Values[j]})
+			}
+			if err != nil {
+				return nil, err
+			}
+			if val == nil {
+				found = false
+				break
+			}
+		}
+		if !found {
+			// not the element we are looking for, keep it in the Content
+			if len(e.Values) > 0 {
+				newContent = append(newContent, elem)
+			}
+			continue
+		}
+		matchingElementFound = true
+
+		// deletion operation -- remove the element from the new Content
+		if e.Element == nil {
+			continue
+		}
+		// replace operation -- replace the element in the Content
+		newContent = append(newContent, e.Element)
+	}
+	rn.YNode().Content = newContent
+
+	// deletion operation -- return nil
+	if IsMissingOrNull(NewRNode(e.Element)) {
+		return nil, nil
+	}
+
+	// append operation -- add the element to the Content
+	if !matchingElementFound {
+		rn.YNode().Content = append(rn.YNode().Content, e.Element)
+	}
+
+	return NewRNode(e.Element), nil
+}
+
+// GetElementByIndex will return a Filter which can be applied to a sequence
+// node to get the element specified by the index
+func GetElementByIndex(index int) ElementIndexer {
+	return ElementIndexer{Index: index}
+}
+
+// ElementIndexer picks the element with a specified index. Index starts from
+// 0 to len(list) - 1. a hyphen ("-") means the last index.
+type ElementIndexer struct {
+	Index int
+}
+
+// Filter implements Filter
+func (i ElementIndexer) Filter(rn *RNode) (*RNode, error) {
+	// rn.Elements will return error if rn is not a sequence node.
+	elems, err := rn.Elements()
+	if err != nil {
+		return nil, err
+	}
+	if i.Index < 0 {
+		return elems[len(elems)-1], nil
+	}
+	if i.Index >= len(elems) {
+		return nil, nil
+	}
+	return elems[i.Index], nil
+}
+
+// Clear returns a FieldClearer
+func Clear(name string) FieldClearer {
+	return FieldClearer{Name: name}
+}
+
+// FieldClearer removes the field or map key.
+// Returns a RNode with the removed field or map entry.
+type FieldClearer struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Name is the name of the field or key in the map.
+	Name string `yaml:"name,omitempty"`
+
+	IfEmpty bool `yaml:"ifEmpty,omitempty"`
+}
+
+func (c FieldClearer) Filter(rn *RNode) (*RNode, error) {
+	if err := ErrorIfInvalid(rn, yaml.MappingNode); err != nil {
+		return nil, err
+	}
+
+	for i := 0; i < len(rn.Content()); i += 2 {
+		// if name matches, remove these 2 elements from the list because
+		// they are treated as a fieldName/fieldValue pair.
+		if rn.Content()[i].Value == c.Name {
+			if c.IfEmpty {
+				if len(rn.Content()[i+1].Content) > 0 {
+					continue
+				}
+			}
+
+			// save the item we are about to remove
+			removed := NewRNode(rn.Content()[i+1])
+			if len(rn.YNode().Content) > i+2 {
+				l := len(rn.YNode().Content)
+				// remove from the middle of the list
+				rn.YNode().Content = rn.Content()[:i]
+				rn.YNode().Content = append(
+					rn.YNode().Content,
+					rn.Content()[i+2:l]...)
+			} else {
+				// remove from the end of the list
+				rn.YNode().Content = rn.Content()[:i]
+			}
+
+			// return the removed field name and value
+			return removed, nil
+		}
+	}
+	// nothing removed
+	return nil, nil
+}
+
+func MatchElement(field, value string) ElementMatcher {
+	return ElementMatcher{Keys: []string{field}, Values: []string{value}}
+}
+
+func MatchElementList(keys []string, values []string) ElementMatcher {
+	return ElementMatcher{Keys: keys, Values: values}
+}
+
+func GetElementByKey(key string) ElementMatcher {
+	return ElementMatcher{Keys: []string{key}, MatchAnyValue: true}
+}
+
+// ElementMatcher returns the first element from a Sequence matching the
+// specified key-value pairs. If there's no match, and no configuration error,
+// the matcher returns nil, nil.
+type ElementMatcher struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Keys are the list of fields upon which to match this element.
+	Keys []string
+
+	// Values are the list of values upon which to match this element.
+	Values []string
+
+	// Create will create the Element if it is not found
+	Create *RNode `yaml:"create,omitempty"`
+
+	// MatchAnyValue indicates that matcher should only consider the key and ignore
+	// the actual value in the list. Values must be empty when MatchAnyValue is
+	// set to true.
+	MatchAnyValue bool `yaml:"noValue,omitempty"`
+}
+
+func (e ElementMatcher) Filter(rn *RNode) (*RNode, error) {
+	if len(e.Keys) == 0 {
+		e.Keys = append(e.Keys, "")
+	}
+	if len(e.Values) == 0 {
+		e.Values = append(e.Values, "")
+	}
+
+	if err := ErrorIfInvalid(rn, yaml.SequenceNode); err != nil {
+		return nil, err
+	}
+	if e.MatchAnyValue && len(e.Values) != 0 && e.Values[0] != "" {
+		return nil, fmt.Errorf("Values must be empty when MatchAnyValue is set to true")
+	}
+
+	// SequenceNode Content is a slice of ScalarNodes.  Each ScalarNode has a
+	// YNode containing the primitive data.
+	if len(e.Keys) == 0 || len(e.Keys[0]) == 0 {
+		for i := range rn.Content() {
+			if rn.Content()[i].Value == e.Values[0] {
+				return &RNode{value: rn.Content()[i]}, nil
+			}
+		}
+		if e.Create != nil {
+			return rn.Pipe(Append(e.Create.YNode()))
+		}
+		return nil, nil
+	}
+
+	// SequenceNode Content is a slice of MappingNodes.  Each MappingNode has Content
+	// with a slice of key-value pairs containing the fields.
+	for i := range rn.Content() {
+		// cast the entry to a RNode so we can operate on it
+		elem := NewRNode(rn.Content()[i])
+		var field *RNode
+		var err error
+
+		// only check mapping node
+		if err = ErrorIfInvalid(elem, yaml.MappingNode); err != nil {
+			continue
+		}
+
+		if !e.MatchAnyValue && len(e.Keys) != len(e.Values) {
+			return nil, fmt.Errorf("length of keys must equal length of values when MatchAnyValue is false")
+		}
+
+		matchesElement := true
+		for i := range e.Keys {
+			if e.MatchAnyValue {
+				field, err = elem.Pipe(Get(e.Keys[i]))
+			} else {
+				field, err = elem.Pipe(MatchField(e.Keys[i], e.Values[i]))
+			}
+			if !IsFoundOrError(field, err) {
+				// this is not the element we are looking for
+				matchesElement = false
+				break
+			}
+		}
+		if matchesElement {
+			return elem, err
+		}
+	}
+
+	// create the element
+	if e.Create != nil {
+		return rn.Pipe(Append(e.Create.YNode()))
+	}
+
+	return nil, nil
+}
+
+func Get(name string) FieldMatcher {
+	return FieldMatcher{Name: name}
+}
+
+func MatchField(name, value string) FieldMatcher {
+	return FieldMatcher{Name: name, Value: NewScalarRNode(value)}
+}
+
+func Match(value string) FieldMatcher {
+	return FieldMatcher{Value: NewScalarRNode(value)}
+}
+
+// FieldMatcher returns the value of a named field or map entry.
+type FieldMatcher struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Name of the field to return
+	Name string `yaml:"name,omitempty"`
+
+	// YNode of the field to return.
+	// Optional.  Will only need to match field name if unset.
+	Value *RNode `yaml:"value,omitempty"`
+
+	StringValue string `yaml:"stringValue,omitempty"`
+
+	StringRegexValue string `yaml:"stringRegexValue,omitempty"`
+
+	// Create will cause the field to be created with this value
+	// if it is set.
+	Create *RNode `yaml:"create,omitempty"`
+}
+
+func (f FieldMatcher) Filter(rn *RNode) (*RNode, error) {
+	if f.StringValue != "" && f.Value == nil {
+		f.Value = NewScalarRNode(f.StringValue)
+	}
+
+	// never match nil or null fields
+	if IsMissingOrNull(rn) {
+		return nil, nil
+	}
+
+	if f.Name == "" {
+		if err := ErrorIfInvalid(rn, yaml.ScalarNode); err != nil {
+			return nil, err
+		}
+		switch {
+		case f.StringRegexValue != "":
+			// TODO(pwittrock): pre-compile this when unmarshalling and cache to a field
+			rg, err := regexp.Compile(f.StringRegexValue)
+			if err != nil {
+				return nil, err
+			}
+			if match := rg.MatchString(rn.value.Value); match {
+				return rn, nil
+			}
+			return nil, nil
+		case GetValue(rn) == GetValue(f.Value):
+			return rn, nil
+		default:
+			return nil, nil
+		}
+	}
+
+	if err := ErrorIfInvalid(rn, yaml.MappingNode); err != nil {
+		return nil, err
+	}
+
+	for i := 0; i < len(rn.Content()); i = IncrementFieldIndex(i) {
+		isMatchingField := rn.Content()[i].Value == f.Name
+		if isMatchingField {
+			requireMatchFieldValue := f.Value != nil
+			if !requireMatchFieldValue || rn.Content()[i+1].Value == f.Value.YNode().Value {
+				return NewRNode(rn.Content()[i+1]), nil
+			}
+		}
+	}
+
+	if f.Create != nil {
+		return rn.Pipe(SetField(f.Name, f.Create))
+	}
+
+	return nil, nil
+}
+
+// Lookup returns a PathGetter to lookup a field by its path.
+func Lookup(path ...string) PathGetter {
+	return PathGetter{Path: path}
+}
+
+// Lookup returns a PathGetter to lookup a field by its path and create it if it doesn't already
+// exist.
+func LookupCreate(kind yaml.Kind, path ...string) PathGetter {
+	return PathGetter{Path: path, Create: kind}
+}
+
+// PathGetter returns the RNode under Path.
+type PathGetter struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Path is a slice of parts leading to the RNode to lookup.
+	// Each path part may be one of:
+	// * FieldMatcher -- e.g. "spec"
+	// * Map Key -- e.g. "app.k8s.io/version"
+	// * List Entry -- e.g. "[name=nginx]" or "[=-jar]" or "0" or "-"
+	//
+	// Map Keys and Fields are equivalent.
+	// See FieldMatcher for more on Fields and Map Keys.
+	//
+	// List Entries can be specified as map entry to match [fieldName=fieldValue]
+	// or a positional index like 0 to get the element. - (unquoted hyphen) is
+	// special and means the last element.
+	//
+	// See Elem for more on List Entries.
+	//
+	// Examples:
+	// * spec.template.spec.container with matching name: [name=nginx]
+	// * spec.template.spec.container.argument matching a value: [=-jar]
+	Path []string `yaml:"path,omitempty"`
+
+	// Create will cause missing path parts to be created as they are walked.
+	//
+	// * The leaf Node (final path) will be created with a Kind matching Create
+	// * Intermediary Nodes will be created as either a MappingNodes or
+	//   SequenceNodes as appropriate for each's Path location.
+	// * If a list item is specified by a index (an offset or "-"), this item will
+	//   not be created even Create is set.
+	Create yaml.Kind `yaml:"create,omitempty"`
+
+	// Style is the style to apply to created value Nodes.
+	// Created key Nodes keep an unspecified Style.
+	Style yaml.Style `yaml:"style,omitempty"`
+}
+
+func (l PathGetter) Filter(rn *RNode) (*RNode, error) {
+	var err error
+	fieldPath := append([]string{}, rn.FieldPath()...)
+	match := rn
+
+	// iterate over path until encountering an error or missing value
+	l.Path = cleanPath(l.Path)
+	for i := range l.Path {
+		var part, nextPart string
+		part = l.Path[i]
+		if len(l.Path) > i+1 {
+			nextPart = l.Path[i+1]
+		}
+		var fltr Filter
+		fltr, err = l.getFilter(part, nextPart, &fieldPath)
+		if err != nil {
+			return nil, err
+		}
+		match, err = match.Pipe(fltr)
+		if IsMissingOrError(match, err) {
+			return nil, err
+		}
+		match.AppendToFieldPath(fieldPath...)
+	}
+	return match, nil
+}
+
+func (l PathGetter) getFilter(part, nextPart string, fieldPath *[]string) (Filter, error) {
+	idx, err := strconv.Atoi(part)
+	switch {
+	case err == nil:
+		// part is a number
+		if idx < 0 {
+			return nil, fmt.Errorf("array index %d cannot be negative", idx)
+		}
+		return GetElementByIndex(idx), nil
+	case part == "-":
+		// part is a hyphen
+		return GetElementByIndex(-1), nil
+	case IsListIndex(part):
+		// part is surrounded by brackets
+		return l.elemFilter(part)
+	default:
+		// mapping node
+		*fieldPath = append(*fieldPath, part)
+		return l.fieldFilter(part, l.getKind(nextPart))
+	}
+}
+
+func (l PathGetter) elemFilter(part string) (Filter, error) {
+	var match *RNode
+	name, value, err := SplitIndexNameValue(part)
+	if err != nil {
+		return nil, errors.Wrap(err)
+	}
+	if !IsCreate(l.Create) {
+		return MatchElement(name, value), nil
+	}
+
+	var elem *RNode
+	primitiveElement := len(name) == 0
+	if primitiveElement {
+		// append a ScalarNode
+		elem = NewScalarRNode(value)
+		elem.YNode().Style = l.Style
+		match = elem
+	} else {
+		// append a MappingNode
+		match = NewRNode(&yaml.Node{Kind: yaml.ScalarNode, Value: value, Style: l.Style})
+		elem = NewRNode(&yaml.Node{
+			Kind:    yaml.MappingNode,
+			Content: []*yaml.Node{{Kind: yaml.ScalarNode, Value: name}, match.YNode()},
+			Style:   l.Style,
+		})
+	}
+	// Append the Node
+	return ElementMatcher{Keys: []string{name}, Values: []string{value}, Create: elem}, nil
+}
+
+func (l PathGetter) fieldFilter(
+	name string, kind yaml.Kind) (Filter, error) {
+	if !IsCreate(l.Create) {
+		return Get(name), nil
+	}
+	return FieldMatcher{Name: name, Create: &RNode{value: &yaml.Node{Kind: kind, Style: l.Style}}}, nil
+}
+
+func (l PathGetter) getKind(nextPart string) yaml.Kind {
+	if IsListIndex(nextPart) {
+		// if nextPart is of the form [a=b], then it is an index into a Sequence
+		// so the current part must be a SequenceNode
+		return yaml.SequenceNode
+	}
+	if nextPart == "" {
+		// final name in the path, use the l.Create defined Kind
+		return l.Create
+	}
+
+	// non-sequence intermediate Node
+	return yaml.MappingNode
+}
+
+func SetField(name string, value *RNode) FieldSetter {
+	return FieldSetter{Name: name, Value: value}
+}
+
+func Set(value *RNode) FieldSetter {
+	return FieldSetter{Value: value}
+}
+
+// FieldSetter sets a field or map entry to a value.
+type FieldSetter struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Name is the name of the field or key to lookup in a MappingNode.
+	// If Name is unspecified, and the input is a ScalarNode, FieldSetter will set the
+	// value on the ScalarNode.
+	Name string `yaml:"name,omitempty"`
+
+	// Comments for the field
+	Comments Comments `yaml:"comments,omitempty"`
+
+	// Value is the value to set.
+	// Optional if Kind is set.
+	Value *RNode `yaml:"value,omitempty"`
+
+	StringValue string `yaml:"stringValue,omitempty"`
+
+	// OverrideStyle can be set to override the style of the existing node
+	// when setting it.  Otherwise, if an existing node is found, the style is
+	// retained.
+	OverrideStyle bool `yaml:"overrideStyle,omitempty"`
+}
+
+func (s FieldSetter) Filter(rn *RNode) (*RNode, error) {
+	if s.StringValue != "" && s.Value == nil {
+		s.Value = NewScalarRNode(s.StringValue)
+	}
+
+	if s.Name == "" {
+		if err := ErrorIfInvalid(rn, yaml.ScalarNode); err != nil {
+			return rn, err
+		}
+		if IsMissingOrNull(s.Value) {
+			return rn, nil
+		}
+		// only apply the style if there is not an existing style
+		// or we want to override it
+		if !s.OverrideStyle || s.Value.YNode().Style == 0 {
+			// keep the original style if it exists
+			s.Value.YNode().Style = rn.YNode().Style
+		}
+		rn.SetYNode(s.Value.YNode())
+		return rn, nil
+	}
+
+	// Clear the field if it is empty, or explicitly null
+	if s.Value == nil || s.Value.IsTaggedNull() {
+		return rn.Pipe(Clear(s.Name))
+	}
+
+	field, err := rn.Pipe(FieldMatcher{Name: s.Name})
+	if err != nil {
+		return nil, err
+	}
+	if field != nil {
+		// only apply the style if there is not an existing style
+		// or we want to override it
+		if !s.OverrideStyle || field.YNode().Style == 0 {
+			// keep the original style if it exists
+			s.Value.YNode().Style = field.YNode().Style
+		}
+		// need to def ref the Node since field is ephemeral
+		field.SetYNode(s.Value.YNode())
+		return field, nil
+	}
+
+	// create the field
+	rn.YNode().Content = append(
+		rn.YNode().Content,
+		&yaml.Node{
+			Kind:        yaml.ScalarNode,
+			Value:       s.Name,
+			HeadComment: s.Comments.HeadComment,
+			LineComment: s.Comments.LineComment,
+			FootComment: s.Comments.FootComment,
+		},
+		s.Value.YNode())
+	return s.Value, nil
+}
+
+// Tee calls the provided Filters, and returns its argument rather than the result
+// of the filters.
+// May be used to fork sub-filters from a call.
+// e.g. locate field, set value; locate another field, set another value
+func Tee(filters ...Filter) Filter {
+	return TeePiper{Filters: filters}
+}
+
+// TeePiper Calls a slice of Filters and returns its input.
+// May be used to fork sub-filters from a call.
+// e.g. locate field, set value; locate another field, set another value
+type TeePiper struct {
+	Kind string `yaml:"kind,omitempty"`
+
+	// Filters are the set of Filters run by TeePiper.
+	Filters []Filter `yaml:"filters,omitempty"`
+}
+
+func (t TeePiper) Filter(rn *RNode) (*RNode, error) {
+	_, err := rn.Pipe(t.Filters...)
+	return rn, err
+}
+
+// IsCreate returns true if kind is specified
+func IsCreate(kind yaml.Kind) bool {
+	return kind != 0
+}
+
+// IsMissingOrError returns true if rn is NOT found or err is non-nil
+func IsMissingOrError(rn *RNode, err error) bool {
+	return rn == nil || err != nil
+}
+
+// IsFoundOrError returns true if rn is found or err is non-nil
+func IsFoundOrError(rn *RNode, err error) bool {
+	return rn != nil || err != nil
+}
+
+func ErrorIfAnyInvalidAndNonNull(kind yaml.Kind, rn ...*RNode) error {
+	for i := range rn {
+		if IsMissingOrNull(rn[i]) {
+			continue
+		}
+		if err := ErrorIfInvalid(rn[i], kind); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+var nodeTypeIndex = map[yaml.Kind]string{
+	yaml.SequenceNode: "SequenceNode",
+	yaml.MappingNode:  "MappingNode",
+	yaml.ScalarNode:   "ScalarNode",
+	yaml.DocumentNode: "DocumentNode",
+	yaml.AliasNode:    "AliasNode",
+}
+
+func ErrorIfInvalid(rn *RNode, kind yaml.Kind) error {
+	if IsMissingOrNull(rn) {
+		// node has no type, pass validation
+		return nil
+	}
+
+	if rn.YNode().Kind != kind {
+		s, _ := rn.String()
+		return errors.Errorf(
+			"wrong Node Kind for %s expected: %v was %v: value: {%s}",
+			strings.Join(rn.FieldPath(), "."),
+			nodeTypeIndex[kind], nodeTypeIndex[rn.YNode().Kind], strings.TrimSpace(s))
+	}
+
+	if kind == yaml.MappingNode {
+		if len(rn.YNode().Content)%2 != 0 {
+			return errors.Errorf(
+				"yaml MappingNodes must have even length contents: %v", spew.Sdump(rn))
+		}
+	}
+
+	return nil
+}
+
+// IsListIndex returns true if p is an index into a Val.
+// e.g. [fieldName=fieldValue]
+// e.g. [=primitiveValue]
+func IsListIndex(p string) bool {
+	return strings.HasPrefix(p, "[") && strings.HasSuffix(p, "]")
+}
+
+// SplitIndexNameValue splits a lookup part Val index into the field name
+// and field value to match.
+// e.g. splits [name=nginx] into (name, nginx)
+// e.g. splits [=-jar] into ("", -jar)
+func SplitIndexNameValue(p string) (string, string, error) {
+	elem := strings.TrimSuffix(p, "]")
+	elem = strings.TrimPrefix(elem, "[")
+	parts := strings.SplitN(elem, "=", 2)
+	if len(parts) == 1 {
+		return "", "", fmt.Errorf("list path element must contain fieldName=fieldValue for element to match")
+	}
+	return parts[0], parts[1], nil
+}
+
+// IncrementFieldIndex increments i to point to the next field name element in
+// a slice of Contents.
+func IncrementFieldIndex(i int) int {
+	return i + 2
+}