Add apply gen to controller-tools

cmd/controller-gen/main.go

@@ -141,13 +141,18 @@ func main() {
 	controller-gen object paths=./apis/v1beta1/some_types.go
 
 	# Generate OpenAPI v3 schemas for API packages and merge them into existing CRD manifests
-	controller-gen schemapatch:manifests=./manifests output:dir=./manifests paths=./pkg/apis/... 
+	controller-gen schemapatch:manifests=./manifests output:dir=./manifests paths=./pkg/apis/...
 
 	# Run all the generators for a given project
 	controller-gen paths=./apis/...
 
 	# Explain the markers for generating CRDs, and their arguments
 	controller-gen crd -ww
+
+	# Generate applyconfigurations for CRDs for use with Server Side Apply. They will be placed
+	# into a "ac/" subdirectory
+
+	controller-gen apply paths=./apis/...
 `,
 		RunE: func(c *cobra.Command, rawOpts []string) error {
 			// print version if asked for it

pkg/applyconfigurations/codewriter.go

@@ -0,0 +1,41 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package applyconfigurations
+
+import (
+	"fmt"
+	"io"
+)
+
+// codeWriter assists in writing out Go code lines and blocks to a writer.
+type codeWriter struct {
+	out io.Writer
+}
+
+// Line writes a single line.
+func (c *codeWriter) Line(line string) {
+	if _, err := fmt.Fprintln(c.out, line); err != nil {
+		panic(err)
+	}
+}
+
+// Linef writes a single line with formatting (as per fmt.Sprintf).
+func (c *codeWriter) Linef(line string, args ...interface{}) {
+	if _, err := fmt.Fprintf(c.out, line+"\n", args...); err != nil {
+		panic(err)
+	}
+}