Preserving code from kubernetes-sigs#5221

Preserving code from
kubernetes-sigs#5221 for investigation
and future improvements

api/filters/replacement/replacement.go

@@ -4,13 +4,13 @@
 package replacement
 
 import (
+	"errors"
 	"fmt"
 	"strings"
 
 	"sigs.k8s.io/kustomize/api/internal/utils"
 	"sigs.k8s.io/kustomize/api/resource"
 	"sigs.k8s.io/kustomize/api/types"
-	"sigs.k8s.io/kustomize/kyaml/errors"
 	"sigs.k8s.io/kustomize/kyaml/resid"
 	kyaml_utils "sigs.k8s.io/kustomize/kyaml/utils"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
@@ -105,7 +105,7 @@ func getRefinedValue(options *types.FieldOptions, rn *yaml.RNode) (*yaml.RNode,
 func applyReplacement(nodes []*yaml.RNode, value *yaml.RNode, targetSelectors []*types.TargetSelector) ([]*yaml.RNode, error) {
 	for _, selector := range targetSelectors {
 		if selector.Select == nil {
-			return nil, errors.Errorf("target must specify resources to select")
+			return nil, errors.New("target must specify resources to select")
 		}
 		if len(selector.FieldPaths) == 0 {
 			selector.FieldPaths = []string{types.DefaultReplacementFieldPath}
@@ -179,38 +179,39 @@ func rejectId(rejects []*types.Selector, id *resid.ResId) bool {
 
 func copyValueToTarget(target *yaml.RNode, value *yaml.RNode, selector *types.TargetSelector) error {
 	for _, fp := range selector.FieldPaths {
-		createKind := yaml.Kind(0) // do not create
-		if selector.Options != nil && selector.Options.Create {
-			createKind = value.YNode().Kind
-		}
-		targetFieldList, err := target.Pipe(&yaml.PathMatcher{
-			Path:   kyaml_utils.SmarterPathSplitter(fp, "."),
-			Create: createKind})
-		if err != nil {
-			return errors.WrapPrefixf(err, fieldRetrievalError(fp, createKind != 0))
-		}
-		targetFields, err := targetFieldList.Elements()
+		fieldPath := kyaml_utils.SmarterPathSplitter(fp, ".")
+		create, err := shouldCreateField(selector.Options, fieldPath)
 		if err != nil {
-			return errors.WrapPrefixf(err, fieldRetrievalError(fp, createKind != 0))
+			return err
 		}
-		if len(targetFields) == 0 {
-			return errors.Errorf(fieldRetrievalError(fp, createKind != 0))
+
+		var targetFields []*yaml.RNode
+		if create {
+			createdField, createErr := target.Pipe(yaml.LookupCreate(value.YNode().Kind, fieldPath...))
+			if createErr != nil {
+				return fmt.Errorf("error creating replacement node: %w", createErr)
+			}
+			targetFields = append(targetFields, createdField)
+		} else {
+			// may return multiple fields, always wrapped in a sequence node
+			foundFieldSequence, lookupErr := target.Pipe(&yaml.PathMatcher{Path: fieldPath})
+			if lookupErr != nil {
+				return fmt.Errorf("error finding field in replacement target: %w", lookupErr)
+			}
+			targetFields, err = foundFieldSequence.Elements()
+			if err != nil {
+				return fmt.Errorf("error fetching elements in replacement target: %w", err)
+			}
 		}
 
 		for _, t := range targetFields {
 			if err := setFieldValue(selector.Options, t, value); err != nil {
 				return err
 			}
 		}
-	}
-	return nil
-}
 
-func fieldRetrievalError(fieldPath string, isCreate bool) string {
-	if isCreate {
-		return fmt.Sprintf("unable to find or create field %q in replacement target", fieldPath)
 	}
-	return fmt.Sprintf("unable to find field %q in replacement target", fieldPath)
+	return nil
 }
 
 func setFieldValue(options *types.FieldOptions, targetField *yaml.RNode, value *yaml.RNode) error {
@@ -242,3 +243,16 @@ func setFieldValue(options *types.FieldOptions, targetField *yaml.RNode, value *
 
 	return nil
 }
+
+func shouldCreateField(options *types.FieldOptions, fieldPath []string) (bool, error) {
+	if options == nil || !options.Create {
+		return false, nil
+	}
+	// create option is not supported in a wildcard matching
+	for _, f := range fieldPath {
+		if f == "*" {
+			return false, fmt.Errorf("cannot support create option in a multi-value target")
+		}
+	}
+	return true, nil
+}