implement TrackableFilter interface with imagetag

This change updates the imagetag filter to implement the TrackableFilter
interface. This provides the functionality for the user to track which
fields were updated by the imagetag filter.

api/filters/imagetag/imagetag.go

@@ -4,6 +4,7 @@
 package imagetag
 
 import (
+	"sigs.k8s.io/kustomize/api/filters/filtersutil"
 	"sigs.k8s.io/kustomize/api/filters/fsslice"
 	"sigs.k8s.io/kustomize/api/types"
 	"sigs.k8s.io/kustomize/kyaml/kio"
@@ -22,9 +23,17 @@ type Filter struct {
 	// FsSlice contains the FieldSpecs to locate an image field,
 	// e.g. Path: "spec/myContainers[]/image"
 	FsSlice types.FsSlice `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
+
+	trackableSetter filtersutil.TrackableSetter
 }
 
 var _ kio.Filter = Filter{}
+var _ kio.TrackableFilter = &Filter{}
+
+// WithMutationTracker registers a callback which will be invoked each time a field is mutated
+func (f *Filter) WithMutationTracker(callback func(key, value, tag string, node *yaml.RNode)) {
+	f.trackableSetter.WithMutationTracker(callback)
+}
 
 func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
 	_, err := kio.FilterAll(yaml.FilterFunc(f.filter)).Filter(nodes)
@@ -39,9 +48,10 @@ func (f Filter) filter(node *yaml.RNode) (*yaml.RNode, error) {
 		return node, nil
 	}
 	if err := node.PipeE(fsslice.Filter{
-		FsSlice:  f.FsSlice,
+		FsSlice: f.FsSlice,
 		SetValue: imageTagUpdater{
-			ImageTag: f.ImageTag,
+			ImageTag:        f.ImageTag,
+			trackableSetter: f.trackableSetter,
 		}.SetImageValue,
 	}); err != nil {
 		return nil, err

api/filters/imagetag/imagetag_test.go

@@ -10,14 +10,35 @@ import (
 	"github.com/stretchr/testify/assert"
 	filtertest "sigs.k8s.io/kustomize/api/testutils/filtertest"
 	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
 )
 
+type setValueArg struct {
+	Key       string
+	Value     string
+	Tag       string
+	PrevValue string
+}
+
+var setValueArgs []setValueArg
+
+func setValueCallbackStub(key, value, tag string, node *yaml.RNode) {
+	setValueArgs = append(setValueArgs, setValueArg{
+		Key:       key,
+		Value:     value,
+		Tag:       tag,
+		PrevValue: node.YNode().Value,
+	})
+}
+
 func TestImageTagUpdater_Filter(t *testing.T) {
 	testCases := map[string]struct {
-		input          string
-		expectedOutput string
-		filter         Filter
-		fsSlice        types.FsSlice
+		input                string
+		expectedOutput       string
+		filter               Filter
+		fsSlice              types.FsSlice
+		setValueCallback     func(key, value, tag string, node *yaml.RNode)
+		expectedSetValueArgs []setValueArg
 	}{
 		"ignore CustomResourceDefinition": {
 			input: `
@@ -658,17 +679,108 @@ spec:
 				},
 			},
 		},
+		"mutation tracker": {
+			input: `
+group: apps
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: nginx:latest
+        name: nginx-latest
+      - image: foobar:1
+        name: replaced-with-digest
+      - image: postgres:1.8.0
+        name: postgresdb
+      initContainers:
+      - image: nginx
+        name: nginx-notag
+      - image: nginx@sha256:111111111111111111
+        name: nginx-sha256
+      - image: alpine:1.8.0
+        name: init-alpine
+`,
+			expectedOutput: `
+group: apps
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  template:
+    spec:
+      containers:
+      - image: busybox:v3
+        name: nginx-tagged
+      - image: busybox:v3
+        name: nginx-latest
+      - image: foobar:1
+        name: replaced-with-digest
+      - image: postgres:1.8.0
+        name: postgresdb
+      initContainers:
+      - image: busybox:v3
+        name: nginx-notag
+      - image: busybox:v3
+        name: nginx-sha256
+      - image: alpine:1.8.0
+        name: init-alpine
+`,
+			filter: Filter{
+				ImageTag: types.Image{
+					Name:    "nginx",
+					NewName: "busybox",
+					NewTag:  "v3",
+				},
+			},
+			fsSlice: []types.FieldSpec{
+				{
+					Path: "spec/template/spec/containers[]/image",
+				},
+				{
+					Path: "spec/template/spec/initContainers[]/image",
+				},
+			},
+			setValueCallback: setValueCallbackStub,
+			expectedSetValueArgs: []setValueArg{
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx:1.7.9",
+				},
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx:latest",
+				},
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx",
+				},
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx@sha256:111111111111111111",
+				},
+			},
+		},
 	}
 
 	for tn, tc := range testCases {
+		setValueArgs = nil
 		t.Run(tn, func(t *testing.T) {
 			filter := tc.filter
+			filter.WithMutationTracker(tc.setValueCallback)
 			filter.FsSlice = tc.fsSlice
 			if !assert.Equal(t,
 				strings.TrimSpace(tc.expectedOutput),
 				strings.TrimSpace(filtertest.RunFilter(t, tc.input, filter))) {
 				t.FailNow()
 			}
+			assert.Equal(t, tc.expectedSetValueArgs, setValueArgs)
 		})
 	}
 }

api/filters/imagetag/updater.go

@@ -14,8 +14,9 @@ import (
 // that will update the value of the yaml node based on the provided
 // ImageTag if the current value matches the format of an image reference.
 type imageTagUpdater struct {
-	Kind     string      `yaml:"kind,omitempty"`
-	ImageTag types.Image `yaml:"imageTag,omitempty"`
+	Kind            string      `yaml:"kind,omitempty"`
+	ImageTag        types.Image `yaml:"imageTag,omitempty"`
+	trackableSetter filtersutil.TrackableSetter
 }
 
 func (u imageTagUpdater) SetImageValue(rn *yaml.RNode) error {
@@ -40,7 +41,7 @@ func (u imageTagUpdater) SetImageValue(rn *yaml.RNode) error {
 		tag = "@" + u.ImageTag.Digest
 	}
 
-	return filtersutil.SetScalar(name + tag)(rn)
+	return u.trackableSetter.SetScalar(name + tag)(rn)
 }
 
 func (u imageTagUpdater) Filter(rn *yaml.RNode) (*yaml.RNode, error) {