add replacement filter to support replacmenttransformer

api/filters/replacement/doc.go

@@ -0,0 +1,4 @@
+// Package replacement contains a kio.Filter implementation of the kustomize
+// replacement transformer (accepts sources and looks for targets to replace
+// their values with values from the sources).
+package replacement

api/filters/replacement/example_test.go

@@ -0,0 +1,68 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package replacement
+
+import (
+	"bytes"
+	"log"
+	"os"
+
+	"sigs.k8s.io/kustomize/kyaml/kio"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+func ExampleFilter() {
+	f := Filter{}
+	err := yaml.Unmarshal([]byte(`
+replacements:
+- source:
+    kind: Foo2
+    fieldPath: spec.replicas
+  targets:
+  - select:
+      kind: Foo1
+    fieldPaths: 
+    - spec.replicas`), &f)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = kio.Pipeline{
+		Inputs: []kio.Reader{&kio.ByteReader{Reader: bytes.NewBufferString(`
+apiVersion: example.com/v1
+kind: Foo1
+metadata:
+  name: instance
+spec:
+  replicas: 3
+---
+apiVersion: example.com/v1
+kind: Foo2
+metadata:
+  name: instance
+spec:
+  replicas: 99
+`)}},
+		Filters: []kio.Filter{f},
+		Outputs: []kio.Writer{kio.ByteWriter{Writer: os.Stdout}},
+	}.Execute()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Output:
+	// apiVersion: example.com/v1
+	// kind: Foo1
+	// metadata:
+	//   name: instance
+	// spec:
+	//   replicas: 99
+	// ---
+	// apiVersion: example.com/v1
+	// kind: Foo2
+	// metadata:
+	//   name: instance
+	// spec:
+	//   replicas: 99
+}

api/filters/replacement/replacement.go

@@ -0,0 +1,123 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package replacement
+
+import (
+	"fmt"
+	"strings"
+
+	"sigs.k8s.io/kustomize/api/resid"
+	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+type Filter struct {
+	Replacements []types.Replacement
+}
+
+// Filter replaces values of targets with values from sources
+// TODO (#3492): Connect this to a replacement transformer plugin
+func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
+	for _, r := range f.Replacements {
+		if r.Source == nil || r.Targets == nil {
+			return nil, fmt.Errorf("replacements must specify a source and at least one target")
+		}
+		value, err := getReplacement(nodes, &r)
+		if err != nil {
+			return nil, err
+		}
+		nodes, err = applyReplacement(nodes, value, r.Targets)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return nodes, nil
+}
+
+func applyReplacement(nodes []*yaml.RNode, value *yaml.RNode, targets []*types.TargetSelector) ([]*yaml.RNode, error) {
+	for _, t := range targets {
+		if len(t.FieldPaths) == 0 {
+			t.FieldPaths = []string{types.DefaultReplacementFieldPath}
+		}
+		for _, n := range nodes {
+			// TODO (#3492): Don't include matches listed in the `reject` field
+			if t.Select.KrmId.Match(getKrmId(n)) {
+				err := applyToNode(n, value, t)
+				if err != nil {
+					return nil, err
+				}
+			}
+		}
+	}
+	return nodes, nil
+}
+
+func applyToNode(node *yaml.RNode, value *yaml.RNode, target *types.TargetSelector) error {
+	if target.Select == nil {
+		return fmt.Errorf("target must specify resources to select")
+	}
+	for _, fp := range target.FieldPaths {
+		fieldPath := strings.Split(fp, ".")
+		// TODO (#3492): Add tests for map keys in the fieldPath (e.g. .spec.containers[name=nginx])
+		t, err := node.Pipe(yaml.Lookup(fieldPath...))
+		if err != nil {
+			return err
+		}
+		if t != nil {
+			// TODO (#3492): Use the field options to refine interpretation of the field
+			t.SetYNode(value.YNode())
+		}
+	}
+	return nil
+}
+
+func getReplacement(nodes []*yaml.RNode, r *types.Replacement) (*yaml.RNode, error) {
+	source, err := selectSourceNode(nodes, r.Source)
+	if err != nil {
+		return nil, err
+	}
+
+	if r.Source.FieldPath == "" {
+		r.Source.FieldPath = types.DefaultReplacementFieldPath
+	}
+	fieldPath := strings.Split(r.Source.FieldPath, ".")
+
+	// TODO (#3492): Add tests for map keys in the fieldPath (e.g. .spec.containers[name=nginx])
+	rn, err := source.Pipe(yaml.Lookup(fieldPath...))
+	if err != nil {
+		return nil, err
+	}
+	// TODO (#3492): Use the field options to refine interpretation of the field
+	return rn, nil
+}
+
+// selectSourceNode finds the node that matches the selector, returning
+// an error if multiple or none are found
+func selectSourceNode(nodes []*yaml.RNode, selector *types.SourceSelector) (*yaml.RNode, error) {
+	var matches []*yaml.RNode
+	for _, n := range nodes {
+		if selector.KrmId.Match(getKrmId(n)) {
+			if len(matches) > 0 {
+				return nil, fmt.Errorf("more than one match for source %v", selector)
+			}
+			matches = append(matches, n)
+		}
+	}
+	if len(matches) == 0 {
+		return nil, fmt.Errorf("found no matches for source %v", selector)
+	}
+	return matches[0], nil
+}
+
+func getKrmId(n *yaml.RNode) *types.KrmId {
+	ns, _ := n.GetNamespace()
+	apiVersion := yaml.GetValue(n.Field(yaml.APIVersionField).Value)
+	group, version := resid.ParseGroupVersion(apiVersion)
+
+	return &types.KrmId{
+		Gvk:       resid.Gvk{Group: group, Version: version, Kind: n.GetKind()},
+		Name:      n.GetName(),
+		Namespace: ns,
+	}
+}

api/filters/replacement/replacement_test.go

@@ -0,0 +1,336 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package replacement
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	filtertest "sigs.k8s.io/kustomize/api/testutils/filtertest"
+	"sigs.k8s.io/yaml"
+)
+
+func TestFilter(t *testing.T) {
+	testCases := map[string]struct {
+		input        string
+		replacements string
+		expected     string
+		expectedErr  bool
+	}{
+		"simple": {
+			input: `apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: postgres:1.8.0
+        name: postgresdb
+---
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy2
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: postgres:1.8.0
+        name: postgresdb
+`,
+			replacements: `replacements:
+- source:
+    kind: Deployment
+    name: deploy2
+    fieldPath: spec.template.spec.containers.0.image
+  targets:
+  - select:
+      kind: Deployment
+      name: deploy1
+    fieldPaths: 
+    - spec.template.spec.containers.1.image
+`,
+			expected: `apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: nginx:1.7.9
+        name: postgresdb
+---
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy2
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: postgres:1.8.0
+        name: postgresdb
+`,
+		},
+		"complex type": {
+			input: `apiVersion: v1
+kind: Pod
+metadata:
+  name: pod
+spec:
+  containers:
+  - image: busybox
+    name: myapp-container
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: deploy2
+spec:
+  template:
+    spec:
+      containers: {}
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: deploy3
+spec:
+  template:
+    spec:
+      containers: {}
+`,
+			replacements: `replacements:
+- source:
+    kind: Pod
+    name: pod
+    fieldPath: spec.containers
+  targets:
+  - select:
+      kind: Deployment
+    fieldPaths: 
+    - spec.template.spec.containers
+`,
+			expected: `apiVersion: v1
+kind: Pod
+metadata:
+  name: pod
+spec:
+  containers:
+  - image: busybox
+    name: myapp-container
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: deploy2
+spec:
+  template:
+    spec:
+      containers:
+      - image: busybox
+        name: myapp-container
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: deploy3
+spec:
+  template:
+    spec:
+      containers:
+      - image: busybox
+        name: myapp-container
+`,
+		},
+		"from ConfigMap": {
+			input: `apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: deploy
+  labels:
+    foo: bar
+spec:
+  template:
+    metadata:
+      labels:
+        foo: bar
+    spec:
+      containers:
+        - name: command-demo-container
+          image: debian
+          command: ["printenv"]
+          args:
+            - HOSTNAME
+            - PORT
+        - name: busybox
+          image: busybox:latest
+          args:
+            - echo
+            - HOSTNAME
+            - PORT
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: cm
+data:
+  HOSTNAME: example.com
+  PORT: 8080
+`,
+			replacements: `replacements:
+- source:
+    kind: ConfigMap
+    name: cm
+    fieldPath: data.HOSTNAME
+  targets:
+  - select:
+      kind: Deployment
+    fieldPaths:
+    - spec.template.spec.containers.0.args.0
+    - spec.template.spec.containers.1.args.1
+- source:
+    kind: ConfigMap
+    name: cm
+    fieldPath: data.PORT
+  targets:
+  - select:
+      kind: Deployment
+    fieldPaths:
+    - spec.template.spec.containers.0.args.1
+    - spec.template.spec.containers.1.args.2
+`,
+			expected: `apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: deploy
+  labels:
+    foo: bar
+spec:
+  template:
+    metadata:
+      labels:
+        foo: bar
+    spec:
+      containers:
+      - name: command-demo-container
+        image: debian
+        command: ["printenv"]
+        args:
+        - example.com
+        - 8080
+      - name: busybox
+        image: busybox:latest
+        args:
+        - echo
+        - example.com
+        - 8080
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: cm
+data:
+  HOSTNAME: example.com
+  PORT: 8080
+`,
+		},
+		"multiple matches for source select": {
+			input: `apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: postgres:1.8.0
+        name: postgresdb
+---
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy2
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: postgres:1.8.0
+        name: postgresdb
+---
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy3
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: postgres:1.8.0
+        name: postgresdb
+`,
+			replacements: `replacements:
+- source:
+    kind: Deployment
+  targets:
+  - select:
+      kind: Deployment
+`,
+			expectedErr: true,
+		},
+		"replacement has no source": {
+			input: `apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: postgres:1.8.0
+        name: postgresdb
+`,
+			replacements: `replacements:
+- targets:
+  - select:
+      kind: Deployment
+`,
+			expectedErr: true,
+		},
+	}
+
+	for tn, tc := range testCases {
+		t.Run(tn, func(t *testing.T) {
+			f := Filter{}
+			err := yaml.Unmarshal([]byte(tc.replacements), &f)
+			assert.NoError(t, err)
+			actual, err := filtertest.RunFilterE(t, tc.input, f)
+			assert.Equal(t, tc.expectedErr, err != nil)
+			if !tc.expectedErr &&
+				!assert.Equal(t, strings.TrimSpace(tc.expected), strings.TrimSpace(actual)) {
+				t.FailNow()
+			}
+		})
+	}
+}

api/internal/crawl/cmd/backend/main.go

@@ -4,8 +4,9 @@ import (
 	"context"
 	"log"
 	"os"
-	server "sigs.k8s.io/kustomize/api/internal/crawl/backend"
 	"strconv"
+
+	server "sigs.k8s.io/kustomize/api/internal/crawl/backend"
 )
 
 func main() {

api/internal/crawl/crawler/github/crawler.go

@@ -81,7 +81,7 @@ func (gc githubCrawler) Crawl(ctx context.Context,
 	output chan<- crawler.CrawledDocument, seen utils.SeenMap) error {
 
 	ranges := []RangeWithin{
-		RangeWithin{
+		{
 			start: uint64(0),
 			end:   githubMaxFileSize,
 		},

api/internal/crawl/crawler/github/split_search_ranges_test.go

@@ -96,6 +96,6 @@ func TestRangeSizes(t *testing.T) {
 	returnedResult := RangeSizes(s)
 	expectedResult := RangeWithin{uint64(2365), uint64(10000)}
 	if !reflect.DeepEqual(returnedResult, expectedResult) {
-		t.Errorf("RangeSizes expected (%v), got (%v)",expectedResult, returnedResult)
+		t.Errorf("RangeSizes expected (%v), got (%v)", expectedResult, returnedResult)
 	}
 }

api/resmap/selector_test.go

@@ -61,13 +61,13 @@ func TestFindPatchTargets(t *testing.T) {
 	}{
 		"select_01": {
 			target: types.Selector{
-				Name: "name.*",
+				KrmId: types.KrmId{Name: "name.*"},
 			},
 			count: 3,
 		},
 		"select_02": {
 			target: types.Selector{
-				Name:               "name.*",
+				KrmId:              types.KrmId{Name: "name.*"},
 				AnnotationSelector: "foo=bar",
 			},
 			count: 2,
@@ -80,98 +80,102 @@ func TestFindPatchTargets(t *testing.T) {
 		},
 		"select_04": {
 			target: types.Selector{
-				Gvk: resid.Gvk{
-					Kind: "Kind1",
+				KrmId: types.KrmId{
+					Gvk: resid.Gvk{
+						Kind: "Kind1",
+					},
+					Name: "name.*",
 				},
-				Name: "name.*",
 			},
 			count: 2,
 		},
 		"select_05": {
 			target: types.Selector{
-				Name: "NotMatched",
+				KrmId: types.KrmId{Name: "NotMatched"},
 			},
 			count: 0,
 		},
 		"select_06": {
 			target: types.Selector{
-				Name: "",
+				KrmId: types.KrmId{Name: ""},
 			},
 			count: 4,
 		},
 		"select_07": {
 			target: types.Selector{
-				Namespace: "default",
+				KrmId: types.KrmId{Namespace: "default"},
 			},
 			count: 2,
 		},
 		"select_08": {
 			target: types.Selector{
-				Namespace: "",
+				KrmId: types.KrmId{Namespace: ""},
 			},
 			count: 4,
 		},
 		"select_09": {
 			target: types.Selector{
-				Namespace: "default",
-				Name:      "name.*",
-				Gvk: resid.Gvk{
-					Kind: "Kind1",
+				KrmId: types.KrmId{
+					Namespace: "default",
+					Name:      "name.*",
+					Gvk: resid.Gvk{
+						Kind: "Kind1",
+					},
 				},
 			},
 			count: 1,
 		},
 		"select_10": {
 			target: types.Selector{
-				Name: "^name.*",
+				KrmId: types.KrmId{Name: "^name.*"},
 			},
 			count: 3,
 		},
 		"select_11": {
 			target: types.Selector{
-				Name: "name.*$",
+				KrmId: types.KrmId{Name: "name.*$"},
 			},
 			count: 3,
 		},
 		"select_12": {
 			target: types.Selector{
-				Name: "^name.*$",
+				KrmId: types.KrmId{Name: "^name.*$"},
 			},
 			count: 3,
 		},
 		"select_13": {
 			target: types.Selector{
-				Namespace: "^def.*",
+				KrmId: types.KrmId{Namespace: "^def.*"},
 			},
 			count: 2,
 		},
 		"select_14": {
 			target: types.Selector{
-				Namespace: "def.*$",
+				KrmId: types.KrmId{Namespace: "def.*$"},
 			},
 			count: 2,
 		},
 		"select_15": {
 			target: types.Selector{
-				Namespace: "^def.*$",
+				KrmId: types.KrmId{Namespace: "^def.*$"},
 			},
 			count: 2,
 		},
 		"select_16": {
 			target: types.Selector{
-				Namespace: "default",
+				KrmId: types.KrmId{Namespace: "default"},
 			},
 			count: 2,
 		},
 		"select_17": {
 			target: types.Selector{
-				Namespace: "NotMatched",
+				KrmId: types.KrmId{Namespace: "NotMatched"},
 			},
 			count: 0,
 		},
 		"select_18": {
 			target: types.Selector{
-				Namespace: "ns1",
+				KrmId: types.KrmId{Namespace: "ns1"},
 			},
 			count: 1,
 		},

api/types/patch_test.go

@@ -9,13 +9,15 @@ import (
 
 func TestPatchEquals(t *testing.T) {
 	selector := Selector{
-		Gvk: resid.Gvk{
-			Group:   "group",
-			Version: "version",
-			Kind:    "kind",
+		KrmId: KrmId{
+			Gvk: resid.Gvk{
+				Group:   "group",
+				Version: "version",
+				Kind:    "kind",
+			},
+			Name:      "name",
+			Namespace: "namespace",
 		},
-		Name:               "name",
-		Namespace:          "namespace",
 		LabelSelector:      "selector",
 		AnnotationSelector: "selector",
 	}
@@ -38,13 +40,15 @@ func TestPatchEquals(t *testing.T) {
 				Path:  "foo",
 				Patch: "bar",
 				Target: &Selector{
-					Gvk: resid.Gvk{
-						Group:   "group",
-						Version: "version",
-						Kind:    "kind",
+					KrmId: KrmId{
+						Gvk: resid.Gvk{
+							Group:   "group",
+							Version: "version",
+							Kind:    "kind",
+						},
+						Name:      "name",
+						Namespace: "namespace",
 					},
-					Name:               "name",
-					Namespace:          "namespace",
 					LabelSelector:      "selector",
 					AnnotationSelector: "selector",
 				},
@@ -53,13 +57,15 @@ func TestPatchEquals(t *testing.T) {
 				Path:  "foo",
 				Patch: "bar",
 				Target: &Selector{
-					Gvk: resid.Gvk{
-						Group:   "group",
-						Version: "version",
-						Kind:    "kind",
+					KrmId: KrmId{
+						Gvk: resid.Gvk{
+							Group:   "group",
+							Version: "version",
+							Kind:    "kind",
+						},
+						Name:      "name",
+						Namespace: "namespace",
 					},
-					Name:               "name",
-					Namespace:          "namespace",
 					LabelSelector:      "selector",
 					AnnotationSelector: "selector",
 				},

api/types/replacement.go

@@ -1,27 +1,62 @@
-// Copyright 2019 The Kubernetes Authors.
+// Copyright 2021 The Kubernetes Authors.
 // SPDX-License-Identifier: Apache-2.0
 
 package types
 
+const DefaultReplacementFieldPath = "metadata.name"
+
 // Replacement defines how to perform a substitution
 // where it is from and where it is to.
 type Replacement struct {
-	Source *ReplSource `json:"source" yaml:"source"`
-	Target *ReplTarget `json:"target" yaml:"target"`
+	// The source of the value.
+	Source *SourceSelector `json:"source" yaml:"source"`
+
+	// The N fields to write the value to.
+	Targets []*TargetSelector `json:"targets" yaml:"targets"`
 }
 
-// ReplSource defines where a substitution is from
-// It can from two different kinds of sources
-//  - from a field of one resource
-//  - from a string
-type ReplSource struct {
-	ObjRef   *Target `json:"objref,omitempty" yaml:"objref,omitempty"`
-	FieldRef string  `json:"fieldref,omitempty" yaml:"fiedldref,omitempty"`
-	Value    string  `json:"value,omitempty" yaml:"value,omitempty"`
+// SourceSelector is the source of the replacement transformer.
+type SourceSelector struct {
+	// A specific object to read it from.
+	KrmId `json:",inline,omitempty" yaml:",inline,omitempty"`
+
+	// Structured field path expected in the allowed object.
+	FieldPath string `json:"fieldPath" yaml:"fieldPath"`
+
+	// Used to refine the interpretation of the field
+	Options *FieldOptions `json:"options" yaml:"options"`
 }
 
-// ReplTarget defines where a substitution is to.
-type ReplTarget struct {
-	ObjRef    *Selector `json:"objref,omitempty" yaml:"objref,omitempty"`
-	FieldRefs []string  `json:"fieldrefs,omitempty" yaml:"fieldrefs,omitempty"`
+// TargetSelector specifies fields in one or more objects.
+type TargetSelector struct {
+	// Include objects that match this.
+	Select *Selector `json:"select" yaml:"select"`
+
+	// From the allowed set, remove objects that match this.
+	// TODO (#3492): Remove matches listed in the exclude field
+	//  Currently this field is unused
+	Reject *Selector `json:"reject" yaml:"reject"`
+
+	// Structured field paths expected in each allowed object.
+	FieldPaths []string `json:"fieldPaths" yaml:"fieldPaths"`
+
+	// Used to refine the interpretation of the field
+	Options *FieldOptions `json:"options" yaml:"options"`
+}
+
+// FieldPath is a structured field path to the desired object
+// TODO (#3492): Implement use of these options, they are
+//  currently used
+type FieldOptions struct {
+	// Used to split/join the field.
+	Delimiter string `json:"delimiter" yaml:"delimiter"`
+
+	// Which position in the split to consider.
+	Index int `json:"index" yaml:"index"`
+
+	// None, Base64, URL, Hex, etc
+	Encoding string `json:"encoding" yaml:"index"`
+
+	// If field missing, add it
+	Create bool `json:"create" yaml:"create"`
 }

api/types/selector.go

@@ -13,9 +13,8 @@ import (
 // Any resource that matches intersection of all conditions
 // is included in this set.
 type Selector struct {
-	resid.Gvk `json:",inline,omitempty" yaml:",inline,omitempty"`
-	Namespace string `json:"namespace,omitempty" yaml:"namespace,omitempty"`
-	Name      string `json:"name,omitempty" yaml:"name,omitempty"`
+	// KrmId refers to a GVKN/Ns of a resource.
+	KrmId `json:",inline,omitempty" yaml:",inline,omitempty"`
 
 	// AnnotationSelector is a string that follows the label selection expression
 	// https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#api
@@ -28,6 +27,23 @@ type Selector struct {
 	LabelSelector string `json:"labelSelector,omitempty" yaml:"labelSelector,omitempty"`
 }
 
+// KrmId refers to a GVKN/Ns of a resource.
+type KrmId struct {
+	resid.Gvk `json:",inline,omitempty" yaml:",inline,omitempty"`
+	Name      string `json:"name,omitempty" yaml:"name,omitempty"`
+	Namespace string `json:"namespace,omitempty" yaml:"namespace,omitempty"`
+}
+
+// Match returns true if id selects other, i.e. id's fields
+// either match other's or are empty
+func (id *KrmId) Match(other *KrmId) bool {
+	return (id.Group == "" || id.Group == other.Group) &&
+		(id.Version == "" || id.Version == other.Version) &&
+		(id.Kind == "" || id.Kind == other.Kind) &&
+		(id.Name == "" || id.Name == other.Name) &&
+		(id.Namespace == "" || id.Namespace == other.Namespace)
+}
+
 // SelectorRegex is a Selector with regex in GVK
 // Any resource that matches intersection of all conditions
 // is included in this set.

api/types/selector_test.go

@@ -15,10 +15,12 @@ func TestSelectorRegexMatchGvk(t *testing.T) {
 	}{
 		{
 			S: Selector{
-				Gvk: resid.Gvk{
-					Group:   "group",
-					Version: "version",
-					Kind:    "kind",
+				KrmId: KrmId{
+					Gvk: resid.Gvk{
+						Group:   "group",
+						Version: "version",
+						Kind:    "kind",
+					},
 				},
 			},
 			G: resid.Gvk{
@@ -30,10 +32,12 @@ func TestSelectorRegexMatchGvk(t *testing.T) {
 		},
 		{
 			S: Selector{
-				Gvk: resid.Gvk{
-					Group:   "group",
-					Version: "",
-					Kind:    "",
+				KrmId: KrmId{
+					Gvk: resid.Gvk{
+						Group:   "group",
+						Version: "",
+						Kind:    "",
+					},
 				},
 			},
 			G: resid.Gvk{
@@ -45,10 +49,12 @@ func TestSelectorRegexMatchGvk(t *testing.T) {
 		},
 		{
 			S: Selector{
-				Gvk: resid.Gvk{
-					Group:   "group",
-					Version: "version",
-					Kind:    "kind",
+				KrmId: KrmId{
+					Gvk: resid.Gvk{
+						Group:   "group",
+						Version: "version",
+						Kind:    "kind",
+					},
 				},
 			},
 			G: resid.Gvk{
@@ -60,10 +66,12 @@ func TestSelectorRegexMatchGvk(t *testing.T) {
 		},
 		{
 			S: Selector{
-				Gvk: resid.Gvk{
-					Group:   "group",
-					Version: "version",
-					Kind:    "kind",
+				KrmId: KrmId{
+					Gvk: resid.Gvk{
+						Group:   "group",
+						Version: "version",
+						Kind:    "kind",
+					},
 				},
 			},
 			G: resid.Gvk{
@@ -75,10 +83,12 @@ func TestSelectorRegexMatchGvk(t *testing.T) {
 		},
 		{
 			S: Selector{
-				Gvk: resid.Gvk{
-					Group:   "g.*",
-					Version: "\\d+",
-					Kind:    ".{4}",
+				KrmId: KrmId{
+					Gvk: resid.Gvk{
+						Group:   "g.*",
+						Version: "\\d+",
+						Kind:    ".{4}",
+					},
 				},
 			},
 			G: resid.Gvk{
@@ -90,10 +100,12 @@ func TestSelectorRegexMatchGvk(t *testing.T) {
 		},
 		{
 			S: Selector{
-				Gvk: resid.Gvk{
-					Group:   "g.*",
-					Version: "\\d+",
-					Kind:    ".{4}",
+				KrmId: KrmId{
+					Gvk: resid.Gvk{
+						Group:   "g.*",
+						Version: "\\d+",
+						Kind:    ".{4}",
+					},
 				},
 			},
 			G: resid.Gvk{
@@ -125,30 +137,38 @@ func TestSelectorRegexMatchName(t *testing.T) {
 	}{
 		{
 			S: Selector{
-				Name:      "foo",
-				Namespace: "bar",
+				KrmId: KrmId{
+					Name:      "foo",
+					Namespace: "bar",
+				},
 			},
 			Name:     "foo",
 			Expected: true,
 		},
 		{
 			S: Selector{
-				Name:      "foo",
-				Namespace: "bar",
+				KrmId: KrmId{
+					Name:      "foo",
+					Namespace: "bar",
+				},
 			},
 			Name:     "bar",
 			Expected: false,
 		},
 		{
 			S: Selector{
-				Name: "f.*",
+				KrmId: KrmId{
+					Name: "f.*",
+				},
 			},
 			Name:     "foo",
 			Expected: true,
 		},
 		{
 			S: Selector{
-				Name: "b.*",
+				KrmId: KrmId{
+					Name: "b.*",
+				},
 			},
 			Name:     "foo",
 			Expected: false,
@@ -174,30 +194,38 @@ func TestSelectorRegexMatchNamespace(t *testing.T) {
 	}{
 		{
 			S: Selector{
-				Name:      "bar",
-				Namespace: "foo",
+				KrmId: KrmId{
+					Name:      "bar",
+					Namespace: "foo",
+				},
 			},
 			Namespace: "foo",
 			Expected:  true,
 		},
 		{
 			S: Selector{
-				Name:      "foo",
-				Namespace: "bar",
+				KrmId: KrmId{
+					Name:      "foo",
+					Namespace: "bar",
+				},
 			},
 			Namespace: "foo",
 			Expected:  false,
 		},
 		{
 			S: Selector{
-				Namespace: "f.*",
+				KrmId: KrmId{
+					Namespace: "f.*",
+				},
 			},
 			Namespace: "foo",
 			Expected:  true,
 		},
 		{
 			S: Selector{
-				Namespace: "b.*",
+				KrmId: KrmId{
+					Namespace: "b.*",
+				},
 			},
 			Namespace: "foo",
 			Expected:  false,

api/types/var.go

@@ -12,8 +12,6 @@ import (
 	"sigs.k8s.io/kustomize/api/resid"
 )
 
-const defaultFieldPath = "metadata.name"
-
 // Var represents a variable whose value will be sourced
 // from a field in a Kubernetes object.
 type Var struct {
@@ -71,7 +69,7 @@ type FieldSelector struct {
 // defaulting sets reference to field used by default.
 func (v *Var) Defaulting() {
 	if v.FieldRef.FieldPath == "" {
-		v.FieldRef.FieldPath = defaultFieldPath
+		v.FieldRef.FieldPath = DefaultReplacementFieldPath
 	}
 	v.ObjRef.GVK()
 }

api/types/var_test.go

@@ -69,9 +69,9 @@ func TestDefaulting(t *testing.T) {
 		},
 	}
 	v.Defaulting()
-	if v.FieldRef.FieldPath != defaultFieldPath {
+	if v.FieldRef.FieldPath != DefaultReplacementFieldPath {
 		t.Fatalf("expected %s, got %v",
-			defaultFieldPath, v.FieldRef.FieldPath)
+			DefaultReplacementFieldPath, v.FieldRef.FieldPath)
 	}
 }
 
@@ -127,7 +127,7 @@ func TestVarSet(t *testing.T) {
 		t.Fatalf("expected var")
 	}
 	// Confirm defaulting.
-	if v.FieldRef.FieldPath != defaultFieldPath {
+	if v.FieldRef.FieldPath != DefaultReplacementFieldPath {
 		t.Fatalf("unexpected field path: %v", v.FieldRef.FieldPath)
 	}
 	// Confirm sorting.