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feat: add clusterctl migrate command
 - Experimental migration support focuses on v1beta1 to v1beta2 conversions for core Cluster API resources Signed-off-by: Satyam Bhardwaj <[email protected]>
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‎cmd/clusterctl/cmd/migrate.go‎

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/*
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Copyright 2025 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package cmd
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import (
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"fmt"
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"io"
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"os"
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"github.com/spf13/cobra"
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"sigs.k8s.io/cluster-api/cmd/clusterctl/internal/migrate"
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"sigs.k8s.io/cluster-api/cmd/clusterctl/internal/scheme"
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)
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type migrateOptions struct {
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output string
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toVersion string
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}
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var migrateOpts = &migrateOptions{}
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var migrateCmd = &cobra.Command{
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Use: "migrate [SOURCE]",
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Short: "EXPERIMENTAL: Migrate cluster.x-k8s.io resources between API versions",
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Long: `EXPERIMENTAL: Migrate cluster.x-k8s.io resources between API versions.
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This command is EXPERIMENTAL and currently supports only cluster.x-k8s.io core resources
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(Cluster, MachineDeployment, etc.) with v1beta2 as the only supported target version.
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SCOPE AND LIMITATIONS (Experimental Status):
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- Only cluster.x-k8s.io resources are converted
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- Other CAPI API groups are passed through unchanged
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- Currently only supports v1beta2 as target version (--to-version flag must be "v1beta2")
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- ClusterClass patches are not migrated
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- Field order may change and comments will be removed in output
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- API version references are dropped during conversion (except cluster class and external
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remediation references)
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Examples:
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# Migrate from file to stdout
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clusterctl migrate cluster.yaml
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# Migrate from stdin to stdout
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cat cluster.yaml | clusterctl migrate
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# Migrate to output file
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clusterctl migrate cluster.yaml --output migrated-cluster.yaml
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# Explicitly specify target version (currently only v1beta2 is supported)
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clusterctl migrate cluster.yaml --to-version v1beta2`,
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Args: cobra.MaximumNArgs(1),
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RunE: func(cmd *cobra.Command, args []string) error {
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return runMigrate(args)
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},
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}
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func init() {
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migrateCmd.Flags().StringVarP(&migrateOpts.output, "output", "o", "", "Output file path (default: stdout)")
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migrateCmd.Flags().StringVar(&migrateOpts.toVersion, "to-version", "v1beta2", "Target API version for migration (currently only v1beta2 is supported)")
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RootCmd.AddCommand(migrateCmd)
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}
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func runMigrate(args []string) error {
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if migrateOpts.toVersion != "v1beta2" {
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return fmt.Errorf("invalid --to-version value %q: currently only v1beta2 is supported", migrateOpts.toVersion)
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}
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fmt.Fprintf(os.Stderr, "WARNING: This command is EXPERIMENTAL and currently supports only cluster.x-k8s.io resources.\n")
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fmt.Fprintf(os.Stderr, "Only v1beta2 is supported as target version. Other CAPI API groups are passed through unchanged.\n")
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fmt.Fprintf(os.Stderr, "See 'clusterctl migrate --help' for scope, limitations, and usage details.\n\n")
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var input io.Reader
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var inputName string
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if len(args) == 0 {
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input = os.Stdin
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inputName = "stdin"
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} else {
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sourceFile := args[0]
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file, err := os.Open(sourceFile)
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if err != nil {
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return fmt.Errorf("failed to open input file %q: %w", sourceFile, err)
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}
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defer file.Close()
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input = file
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inputName = sourceFile
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}
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// Determine output destination
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var output io.Writer
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var outputFile *os.File
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var err error
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if migrateOpts.output == "" {
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output = os.Stdout
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} else {
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outputFile, err = os.Create(migrateOpts.output)
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if err != nil {
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return fmt.Errorf("failed to create output file %q: %w", migrateOpts.output, err)
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}
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defer outputFile.Close()
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output = outputFile
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}
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// Create migration engine components
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parser := migrate.NewYAMLParser(scheme.Scheme)
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converter, err := migrate.NewConverter()
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if err != nil {
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return fmt.Errorf("failed to create converter: %w", err)
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}
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engine, err := migrate.NewEngine(parser, converter)
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if err != nil {
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return fmt.Errorf("failed to create migration engine: %w", err)
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}
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opts := migrate.MigrationOptions{
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Input: input,
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Output: output,
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Errors: os.Stderr,
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ToVersion: migrateOpts.toVersion,
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}
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result, err := engine.Migrate(opts)
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if err != nil {
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return fmt.Errorf("migration failed: %w", err)
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}
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if result.TotalResources > 0 {
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fmt.Fprintf(os.Stderr, "\nMigration completed:\n")
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fmt.Fprintf(os.Stderr, " Total resources processed: %d\n", result.TotalResources)
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fmt.Fprintf(os.Stderr, " Resources converted: %d\n", result.ConvertedCount)
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fmt.Fprintf(os.Stderr, " Resources skipped: %d\n", result.SkippedCount)
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if result.ErrorCount > 0 {
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fmt.Fprintf(os.Stderr, " Resources with errors: %d\n", result.ErrorCount)
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}
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if len(result.Warnings) > 0 {
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fmt.Fprintf(os.Stderr, " Warnings: %d\n", len(result.Warnings))
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}
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fmt.Fprintf(os.Stderr, "\nSource: %s\n", inputName)
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if migrateOpts.output != "" {
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fmt.Fprintf(os.Stderr, "Output: %s\n", migrateOpts.output)
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}
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}
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if result.ErrorCount > 0 {
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return fmt.Errorf("migration completed with %d errors", result.ErrorCount)
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}
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return nil
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}

‎cmd/clusterctl/internal/migrate/converter.go‎

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/*
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Copyright 2025 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package migrate
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import (
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"fmt"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/runtime/schema"
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"sigs.k8s.io/controller-runtime/pkg/conversion"
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"sigs.k8s.io/cluster-api/cmd/clusterctl/internal/scheme"
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)
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// Converter handles conversion of individual CAPI resources between API versions.
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type Converter struct {
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scheme *runtime.Scheme
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targetGV schema.GroupVersion
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targetGVKMap gvkConversionMap
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}
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// gvkConversionMap caches conversions from a source GroupVersionKind to its target GroupVersionKind.
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type gvkConversionMap map[schema.GroupVersionKind]schema.GroupVersionKind
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// ConversionResult represents the outcome of converting a single resource.
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type ConversionResult struct {
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Object runtime.Object
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// Converted indicates whether the object was actually converted
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Converted bool
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Error error
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Warnings []string
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}
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// NewConverter creates a new resource converter using the clusterctl scheme.
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func NewConverter() (*Converter, error) {
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// Use the clusterctl scheme which has all CAPI versions registered
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targetGV := schema.GroupVersion{Group: "cluster.x-k8s.io", Version: "v1beta2"}
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return &Converter{
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scheme: scheme.Scheme,
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targetGV: targetGV,
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targetGVKMap: make(gvkConversionMap),
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}, nil
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}
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// CanConvert determines if a resource can be converted.
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func (c *Converter) CanConvert(info ResourceInfo, obj runtime.Object) bool {
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gvk := info.GroupVersionKind
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if gvk.Group != "cluster.x-k8s.io" {
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return false
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}
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if gvk.Version == c.targetGV.Version {
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return false
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}
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return true
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}
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// ConvertResource converts a single resource to the target version.
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// Returns the converted object, or the original if no conversion is needed.
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func (c *Converter) ConvertResource(info ResourceInfo, obj runtime.Object) ConversionResult {
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gvk := info.GroupVersionKind
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if gvk.Group == "cluster.x-k8s.io" && gvk.Version == c.targetGV.Version {
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return ConversionResult{
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Object: obj,
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Converted: false,
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Warnings: []string{fmt.Sprintf("Resource %s/%s is already at version %s", gvk.Kind, info.Name, c.targetGV.Version)},
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}
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}
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if gvk.Group != "cluster.x-k8s.io" {
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return ConversionResult{
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Object: obj,
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Converted: false,
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Warnings: []string{fmt.Sprintf("Skipping non-cluster.x-k8s.io resource: %s", gvk.String())},
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}
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}
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targetGVK, err := c.getTargetGVK(gvk)
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if err != nil {
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return ConversionResult{
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Object: obj,
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Converted: false,
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Error: fmt.Errorf("failed to determine target GVK for %s: %w", gvk.String(), err),
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}
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}
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// Check if the object is already typed
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// If it's typed and implements conversion.Convertible, use the custom ConvertTo method
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if convertible, ok := obj.(conversion.Convertible); ok {
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// Create a new instance of the target type
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targetObj, err := c.scheme.New(targetGVK)
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if err != nil {
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return ConversionResult{
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Object: obj,
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Converted: false,
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Error: fmt.Errorf("failed to create target object for %s: %w", targetGVK.String(), err),
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}
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}
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// Check if the target object is a Hub
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if hub, ok := targetObj.(conversion.Hub); ok {
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if err := convertible.ConvertTo(hub); err != nil {
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return ConversionResult{
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Object: obj,
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Converted: false,
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Error: fmt.Errorf("failed to convert %s from %s to %s: %w", gvk.Kind, gvk.Version, c.targetGV.Version, err),
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}
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}
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// Ensure the GVK is set on the converted object
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hubObj := hub.(runtime.Object)
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hubObj.GetObjectKind().SetGroupVersionKind(targetGVK)
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return ConversionResult{
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Object: hubObj,
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Converted: true,
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Error: nil,
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Warnings: nil,
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}
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}
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}
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// Use scheme-based conversion for all remaining cases
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convertedObj, err := c.scheme.ConvertToVersion(obj, targetGVK.GroupVersion())
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if err != nil {
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return ConversionResult{
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Object: obj,
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Converted: false,
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Error: fmt.Errorf("failed to convert %s from %s to %s: %w", gvk.Kind, gvk.Version, c.targetGV.Version, err),
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}
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}
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return ConversionResult{
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Object: convertedObj,
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Converted: true,
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Error: nil,
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Warnings: nil,
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}
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}
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// getTargetGVK returns the target GroupVersionKind for a given source GVK.
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func (c *Converter) getTargetGVK(sourceGVK schema.GroupVersionKind) (schema.GroupVersionKind, error) {
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// Check cache first
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if targetGVK, ok := c.targetGVKMap[sourceGVK]; ok {
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return targetGVK, nil
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}
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// Create target GVK with same kind but target version
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targetGVK := schema.GroupVersionKind{
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Group: c.targetGV.Group,
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Version: c.targetGV.Version,
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Kind: sourceGVK.Kind,
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}
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// Verify the target type exists in the scheme
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if !c.scheme.Recognizes(targetGVK) {
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return schema.GroupVersionKind{}, fmt.Errorf("target GVK %s not recognized by scheme", targetGVK.String())
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}
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// Cache for future use
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c.targetGVKMap[sourceGVK] = targetGVK
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return targetGVK, nil
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}

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