Add server-side apply patch support

This adds a patch type for server-side apply (Kubernetes 1.14+),
which allows you to write code like

```go
client.Patch(ctx, &corev1.Pod{/* fields I care about */}, client.Apply, client.IgnoreConflicts())
```

and have it just work.

Author: DirectXMan12

pkg/client/client_test.go

@@ -276,7 +276,7 @@ var _ = Describe("Client", func() {
 					Expect(cl).NotTo(BeNil())
 
 					By("creating the object (with DryRun)")
-					err = cl.Create(context.TODO(), dep, client.CreateDryRunAll())
+					err = cl.Create(context.TODO(), dep, client.CreateDryRunAll)
 					Expect(err).NotTo(HaveOccurred())
 
 					actual, err := clientset.AppsV1().Deployments(ns).Get(dep.Name, metav1.GetOptions{})
@@ -415,7 +415,7 @@ var _ = Describe("Client", func() {
 				})
 
 				By("creating the object")
-				err = cl.Create(context.TODO(), u, client.CreateDryRunAll())
+				err = cl.Create(context.TODO(), u, client.CreateDryRunAll)
 				Expect(err).NotTo(HaveOccurred())
 
 				actual, err := clientset.AppsV1().Deployments(ns).Get(dep.Name, metav1.GetOptions{})
@@ -1074,7 +1074,7 @@ var _ = Describe("Client", func() {
 				Expect(err).NotTo(HaveOccurred())
 
 				By("patching the Deployment with dry-run")
-				err = cl.Patch(context.TODO(), dep, client.ConstantPatch(types.MergePatchType, mergePatch), client.UpdatePatchWith(client.UpdateDryRunAll()))
+				err = cl.Patch(context.TODO(), dep, client.ConstantPatch(types.MergePatchType, mergePatch), client.PatchDryRunAll)
 				Expect(err).NotTo(HaveOccurred())
 
 				By("validating patched Deployment doesn't have the new annotation")
@@ -1183,7 +1183,7 @@ var _ = Describe("Client", func() {
 					Kind:    "Deployment",
 					Version: "v1",
 				})
-				err = cl.Patch(context.TODO(), u, client.ConstantPatch(types.MergePatchType, mergePatch), client.UpdatePatchWith(client.UpdateDryRunAll()))
+				err = cl.Patch(context.TODO(), u, client.ConstantPatch(types.MergePatchType, mergePatch), client.PatchDryRunAll)
 				Expect(err).NotTo(HaveOccurred())
 
 				By("validating patched Deployment does not have the new annotation")
@@ -2000,7 +2000,7 @@ var _ = Describe("Client", func() {
 	Describe("CreateOptions", func() {
 		It("should allow setting DryRun to 'all'", func() {
 			co := &client.CreateOptions{}
-			client.CreateDryRunAll()(co)
+			client.CreateDryRunAll(co)
 			all := []string{metav1.DryRunAll}
 			Expect(co.AsCreateOptions().DryRun).To(Equal(all))
 		})
@@ -2141,7 +2141,7 @@ var _ = Describe("Client", func() {
 	Describe("UpdateOptions", func() {
 		It("should allow setting DryRun to 'all'", func() {
 			uo := &client.UpdateOptions{}
-			client.UpdateDryRunAll()(uo)
+			client.UpdateDryRunAll(uo)
 			all := []string{metav1.DryRunAll}
 			Expect(uo.AsUpdateOptions().DryRun).To(Equal(all))
 		})

pkg/client/doc.go

@@ -36,6 +36,9 @@ limitations under the License.
 // For instance, to use a label selector on list, you can call
 //  err := someReader.List(context.Background(), &podList, client.MatchingLabels(someLabelMap))
 //
+// Options that take no arguments don't need to be called as a function:
+//  err := someWriter.Update(context.Background(), &pod, client.UpdateDryRunAll)
+//
 // Indexing
 //
 // Indexes may be added to caches using a FieldIndexer.  This allows you to easily

pkg/client/interfaces.go

@@ -41,6 +41,8 @@ type Patch interface {
 	// Type is the PatchType of the patch.
 	Type() types.PatchType
 	// Data is the raw data representing the patch.
+	// It receives the object passed to client.Patch, in order to
+	// allow constructing diffs, etc.
 	Data(obj runtime.Object) ([]byte, error)
 }
 

pkg/client/options.go

@@ -21,6 +21,7 @@ import (
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/labels"
 )
+
 // CreateOptions contains options for create requests. It's generally a subset
 // of metav1.CreateOptions.
 type CreateOptions struct {
@@ -66,10 +67,8 @@ type CreateOptionFunc func(*CreateOptions)
 
 // CreateDryRunAll is a functional option that sets the DryRun
 // field of a CreateOptions struct to metav1.DryRunAll.
-func CreateDryRunAll() CreateOptionFunc {
-	return func(opts *CreateOptions) {
-		opts.DryRun = []string{metav1.DryRunAll}
-	}
+var CreateDryRunAll CreateOptionFunc = func(opts *CreateOptions) {
+	opts.DryRun = []string{metav1.DryRunAll}
 }
 
 // DeleteOptions contains options for delete requests. It's generally a subset
@@ -338,15 +337,26 @@ type UpdateOptionFunc func(*UpdateOptions)
 
 // UpdateDryRunAll is a functional option that sets the DryRun
 // field of a UpdateOptions struct to metav1.DryRunAll.
-func UpdateDryRunAll() UpdateOptionFunc {
-	return func(opts *UpdateOptions) {
-		opts.DryRun = []string{metav1.DryRunAll}
-	}
+var UpdateDryRunAll UpdateOptionFunc = func(opts *UpdateOptions) {
+	opts.DryRun = []string{metav1.DryRunAll}
 }
 
 // PatchOptions contains options for patch requests.
 type PatchOptions struct {
-	UpdateOptions
+	// When present, indicates that modifications should not be
+	// persisted. An invalid or unrecognized dryRun directive will
+	// result in an error response and no further processing of the
+	// request. Valid values are:
+	// - All: all dry run stages will be processed
+	DryRun []string
+	
+	// Force ignores conflicts during server-side apply,
+	// re-marking ownership of any fields that aren't already owned.
+	// It's probably what controllers want to do.
+	Force *bool
+
+	// Raw represets raw patch options, passed directly to the server.
+	Raw *metav1.PatchOptions
 }
 
 // ApplyOptions executes the given PatchOptionFuncs, mutating these PatchOptions.
@@ -358,19 +368,35 @@ func (o *PatchOptions) ApplyOptions(optFuncs []PatchOptionFunc) *PatchOptions {
 	return o
 }
 
+func (o *PatchOptions) AsPatchOptions() *metav1.PatchOptions {
+	if o == nil {
+		return &metav1.PatchOptions{}
+	}
+	if o.Raw == nil {
+		o.Raw = &metav1.PatchOptions{}
+	}
+
+	o.Raw.DryRun = o.DryRun
+	o.Raw.Force = o.Force
+	return o.Raw
+}
+
 // PatchOptionFunc is a function that mutates a PatchOptions struct. It implements
 // the functional options pattern. See
 // https://github.com/tmrts/go-patterns/blob/master/idiom/functional-options.md.
 type PatchOptionFunc func(*PatchOptions)
 
-// Sadly, we need a separate function to "adapt" PatchOptions to the constituent
-// update options, since there's no way to write a function that works for both.
+// ForceOwnership sets the Force option, indicating that
+// in case of conflicts with server-side apply, the client should
+// acquire ownership of the conflicting field.  Most controllers
+// should use this.
+var ForceOwnership PatchOptionFunc = func(opts *PatchOptions) {
+	definitelyTrue := true
+	opts.Force = &definitelyTrue
+}
 
-// UpdatePatchWith adapts the given UpdateOptionFuncs to be a PatchOptionFunc.
-func UpdatePatchWith(optFuncs ...UpdateOptionFunc) PatchOptionFunc {
-	return func(opts *PatchOptions) {
-		for _, optFunc := range optFuncs {
-			optFunc(&opts.UpdateOptions)
-		}
-	}
+// PatchDryRunAll is a functional option that sets the DryRun
+// field of a CreateOptions struct to metav1.DryRunAll.
+var PatchDryRunAll PatchOptionFunc = func(opts *PatchOptions) {
+	opts.DryRun = []string{metav1.DryRunAll}
 }

pkg/client/patch.go

@@ -23,6 +23,11 @@ import (
 	"k8s.io/apimachinery/pkg/util/strategicpatch"
 )
 
+var (
+	// Apply uses server-side apply to patch the given object.
+	Apply = applyPatch{}
+)
+
 type patch struct {
 	patchType types.PatchType
 	data      []byte
@@ -47,7 +52,7 @@ type mergeFromPatch struct {
 	from runtime.Object
 }
 
-// Type implements patch.
+// Type implements Patch.
 func (s *mergeFromPatch) Type() types.PatchType {
 	return types.StrategicMergePatchType
 }
@@ -72,3 +77,21 @@ func (s *mergeFromPatch) Data(obj runtime.Object) ([]byte, error) {
 func MergeFrom(obj runtime.Object) Patch {
 	return &mergeFromPatch{obj}
 }
+
+// applyPatch uses server-side apply to patch the object.
+type applyPatch struct{}
+
+// Type implements Patch.
+func (p applyPatch) Type() types.PatchType {
+	// TODO(directxman12): when we update to 1.14, just use types.ApplyPatch
+	return "application/apply-patch+yaml"
+}
+
+// Data implements Patch.
+func (p applyPatch) Data(obj runtime.Object) ([]byte, error) {
+	// NB(directxman12): we might techically want to be using an actual encoder
+	// here (in case some more performant encoder is introduced) but this is
+	// correct and sufficient for our uses (it's what the JSON serializer in
+	// client-go does, more-or-less).
+	return json.Marshal(obj)
+}

pkg/client/typed_client.go

@@ -103,7 +103,7 @@ func (c *typedClient) Patch(ctx context.Context, obj runtime.Object, patch Patch
 		NamespaceIfScoped(o.GetNamespace(), o.isNamespaced()).
 		Resource(o.resource()).
 		Name(o.GetName()).
-		VersionedParams(patchOpts.ApplyOptions(opts).AsUpdateOptions(), c.paramCodec).
+		VersionedParams(patchOpts.ApplyOptions(opts).AsPatchOptions(), c.paramCodec).
 		Body(data).
 		Context(ctx).
 		Do().

pkg/client/unstructured_client.go

@@ -108,7 +108,7 @@ func (uc *unstructuredClient) Patch(_ context.Context, obj runtime.Object, patch
 	}
 
 	patchOpts := &PatchOptions{}
-	i, err := r.Patch(u.GetName(), patch.Type(), data, *patchOpts.ApplyOptions(opts).AsUpdateOptions())
+	i, err := r.Patch(u.GetName(), patch.Type(), data, *patchOpts.ApplyOptions(opts).AsPatchOptions())
 	if err != nil {
 		return err
 	}