[Address #3937] Add labels to template/metadata if includeTemplates is true (#4209)

* add labels in template/metadata by default

* update comment

* fix kustomization labels test

* Add spec/template/metadata/labels when includeTemplate is true

* remove unnecessary test changes

* add error wrap

* Revert "add error wrap"

This reverts commit 0a203df83edb90a400b35d5521487b984619e919.

* add error wrap at template fieldSpec merge

api/internal/target/kusttarget_configplugin.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"path/filepath"
 
+	"github.com/pkg/errors"
 	"sigs.k8s.io/kustomize/api/internal/plugins/builtinconfig"
 	"sigs.k8s.io/kustomize/api/internal/plugins/builtinhelpers"
 	"sigs.k8s.io/kustomize/api/resmap"
@@ -285,6 +286,13 @@ var transformerConfigurators = map[builtinhelpers.BuiltinPluginType]func(
 			if label.IncludeSelectors {
 				fss, err = fss.MergeAll(tc.CommonLabels)
 			} else {
+				// merge spec/template/metadata fieldSpec if includeTemplate flag is true
+				if label.IncludeTemplates {
+					fss, err = fss.MergeOne(types.FieldSpec{Path: "spec/template/metadata/labels", CreateIfNotPresent: false})
+					if err != nil {
+						return nil, errors.Wrap(err, "failed to merge template fieldSpec")
+					}
+				}
 				// only add to metadata by default
 				fss, err = fss.MergeOne(types.FieldSpec{Path: "metadata/labels", CreateIfNotPresent: true})
 			}

api/krusty/inlinelabels_test.go

@@ -91,3 +91,72 @@ spec:
     c: d
 `)
 }
+
+func TestKustomizationLabelsInTemplate(t *testing.T) {
+	th := kusttest_test.MakeHarness(t)
+	th.WriteF("app/deployment.yaml", `
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app.kubernetes.io/component: a
+    app.kubernetes.io/instance: b
+    app.kubernetes.io/name: c
+    app.kubernetes.io/part-of: d
+  name: deployment
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/component: a
+      app.kubernetes.io/instance: b
+      app.kubernetes.io/name: c
+      app.kubernetes.io/part-of: d
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/component: a
+        app.kubernetes.io/instance: b
+        app.kubernetes.io/name: c
+        app.kubernetes.io/part-of: d
+`)
+	th.WriteK("/app", `
+resources:
+- deployment.yaml
+
+labels:
+- pairs:
+    foo: bar
+  includeSelectors: false
+  includeTemplates: true
+`)
+	m := th.Run("/app", th.MakeDefaultOptions())
+	th.AssertActualEqualsExpected(m, `
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app.kubernetes.io/component: a
+    app.kubernetes.io/instance: b
+    app.kubernetes.io/name: c
+    app.kubernetes.io/part-of: d
+    foo: bar
+  name: deployment
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/component: a
+      app.kubernetes.io/instance: b
+      app.kubernetes.io/name: c
+      app.kubernetes.io/part-of: d
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/component: a
+        app.kubernetes.io/instance: b
+        app.kubernetes.io/name: c
+        app.kubernetes.io/part-of: d
+        foo: bar
+`)
+}

api/types/labels.go

@@ -10,7 +10,12 @@ type Label struct {
 	// fieldSpecs for selectors. Custom fieldSpecs specified by
 	// FieldSpecs will be merged with builtin fieldSpecs if this
 	// is true.
-	IncludeSelectors bool        `json:"includeSelectors,omitempty" yaml:"includeSelectors,omitempty"`
+	IncludeSelectors bool `json:"includeSelectors,omitempty" yaml:"includeSelectors,omitempty"`
+	// IncludeTemplates inidicates should transformer include the
+	// spec/template/metadata fieldSpec. Custom fieldSpecs specified by
+	// FieldSpecs will be merged with spec/template/metadata fieldSpec if this
+	// is true. If IncludeSelectors is true, IncludeTemplates is not needed.
+	IncludeTemplates bool        `json:"includeTemplates,omitempty" yaml:"includeTemplates,omitempty"`
 	FieldSpecs       []FieldSpec `json:"fields,omitempty" yaml:"fields,omitempty"`
 }