add function to find all matched patch targets

pkg/resmap/resmap.go

@@ -8,6 +8,8 @@ package resmap
 import (
 	"bytes"
 	"fmt"
+	"regexp"
+
 	"github.com/pkg/errors"
 
 	"sigs.k8s.io/kustomize/v3/pkg/resid"
@@ -158,6 +160,10 @@ type ResMap interface {
 
 	// Debug prints the ResMap.
 	Debug(title string)
+
+	// Select returns a list of resources that
+	// are selected by a Selector
+	Select(types.Selector) ([]*resource.Resource, error)
 }
 
 // resWrangler holds the content manipulated by kustomize.
@@ -587,3 +593,66 @@ func (m *resWrangler) appendReplaceOrMerge(
 	}
 	return nil
 }
+
+// Select returns a list of resources that
+// are selected by a Selector
+func (m *resWrangler) Select(s types.Selector) ([]*resource.Resource, error) {
+	ns := regexp.MustCompile(s.Namespace)
+	nm := regexp.MustCompile(s.Name)
+	var result []*resource.Resource
+	for _, r := range m.Resources() {
+		curId := r.CurId()
+		orgId := r.OrgId()
+
+		// matches the namespace when namespace is not empty in the selector
+		// It first tries to match with the original namespace
+		// then matches with the current namespace
+		if r.GetNamespace() != "" {
+			matched := ns.MatchString(orgId.EffectiveNamespace())
+			if !matched {
+				matched = ns.MatchString(curId.EffectiveNamespace())
+				if !matched {
+					continue
+				}
+			}
+		}
+
+		// matches the name when name is not empty in the selector
+		// It first tries to match with the original name
+		// then matches with the current name
+		if r.GetName() != "" {
+			matched := nm.MatchString(orgId.Name)
+			if !matched {
+				matched = nm.MatchString(curId.Name)
+				if !matched {
+					continue
+				}
+			}
+		}
+
+		// matches the GVK
+		if !r.GetGvk().IsSelected(&s.Gvk) {
+			continue
+		}
+
+		// matches the label selector
+		matched, err := r.MatchesLabelSelector(s.LabelSelector)
+		if err != nil {
+			return nil, err
+		}
+		if !matched {
+			continue
+		}
+
+		// matches the annotation selector
+		matched, err = r.MatchesAnnotationSelector(s.AnnotationSelector)
+		if err != nil {
+			return nil, err
+		}
+		if !matched {
+			continue
+		}
+		result = append(result, r)
+	}
+	return result, nil
+}