add v1alpha2 registry based conversion (#1006)

* add v1alpha2 registry based conversion

* test defaults, set our 1st explicit default

* fix typos and dates

* move pluginregistry to its own dir

* remove unused v1alpha2.Namespace type

* move migration code folders, remove switch

* validate internalPolicy a single time

* remove structured logs

* simplify return

* check for nil methods

* properly check before adding default evictor

* add TODO comment

* bump copyright year

pkg/api/v1alpha2/conversion.go

@@ -0,0 +1,136 @@
+/*
+Copyright 2023 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 v1alpha2
+
+import (
+	"fmt"
+	"sync"
+
+	"k8s.io/apimachinery/pkg/conversion"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	api "sigs.k8s.io/descheduler/pkg/api"
+
+	"sigs.k8s.io/descheduler/pkg/framework/pluginregistry"
+)
+
+var (
+	// pluginArgConversionScheme is a scheme with internal and v1alpha2 registered,
+	// used for defaulting/converting typed PluginConfig Args.
+	// Access via getPluginArgConversionScheme()
+	pluginArgConversionScheme     *runtime.Scheme
+	initPluginArgConversionScheme sync.Once
+
+	Scheme = runtime.NewScheme()
+	Codecs = serializer.NewCodecFactory(Scheme, serializer.EnableStrict)
+)
+
+func GetPluginArgConversionScheme() *runtime.Scheme {
+	initPluginArgConversionScheme.Do(func() {
+		// set up the scheme used for plugin arg conversion
+		pluginArgConversionScheme = runtime.NewScheme()
+		utilruntime.Must(AddToScheme(pluginArgConversionScheme))
+		utilruntime.Must(api.AddToScheme(pluginArgConversionScheme))
+	})
+	return pluginArgConversionScheme
+}
+
+func Convert_v1alpha2_DeschedulerPolicy_To_api_DeschedulerPolicy(in *DeschedulerPolicy, out *api.DeschedulerPolicy, s conversion.Scope) error {
+	if err := autoConvert_v1alpha2_DeschedulerPolicy_To_api_DeschedulerPolicy(in, out, s); err != nil {
+		return err
+	}
+	return convertToInternalPluginConfigArgs(out)
+}
+
+// convertToInternalPluginConfigArgs converts PluginConfig#Args into internal
+// types using a scheme, after applying defaults.
+func convertToInternalPluginConfigArgs(out *api.DeschedulerPolicy) error {
+	scheme := GetPluginArgConversionScheme()
+	for i := range out.Profiles {
+		prof := &out.Profiles[i]
+		for j := range prof.PluginConfigs {
+			args := prof.PluginConfigs[j].Args
+			if args == nil {
+				continue
+			}
+			if _, isUnknown := args.(*runtime.Unknown); isUnknown {
+				continue
+			}
+			internalArgs, err := scheme.ConvertToVersion(args, api.SchemeGroupVersion)
+			if err != nil {
+				err = nil
+				internalArgs = args
+				if err != nil {
+					return fmt.Errorf("converting .Profiles[%d].PluginConfigs[%d].Args into internal type: %w", i, j, err)
+				}
+			}
+			prof.PluginConfigs[j].Args = internalArgs
+		}
+	}
+	return nil
+}
+
+func Convert_v1alpha2_PluginConfig_To_api_PluginConfig(in *PluginConfig, out *api.PluginConfig, s conversion.Scope) error {
+	out.Name = in.Name
+	if _, ok := pluginregistry.PluginRegistry[in.Name]; ok {
+		out.Args = pluginregistry.PluginRegistry[in.Name].PluginArgInstance
+		if in.Args.Raw != nil {
+			_, _, err := Codecs.UniversalDecoder().Decode(in.Args.Raw, nil, out.Args)
+			if err != nil {
+				return err
+			}
+		} else if in.Args.Object != nil {
+			out.Args = in.Args.Object
+		}
+	} else {
+		if err := runtime.Convert_runtime_RawExtension_To_runtime_Object(&in.Args, &out.Args, s); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func Convert_api_DeschedulerPolicy_To_v1alpha2_DeschedulerPolicy(in *api.DeschedulerPolicy, out *DeschedulerPolicy, s conversion.Scope) error {
+	if err := autoConvert_api_DeschedulerPolicy_To_v1alpha2_DeschedulerPolicy(in, out, s); err != nil {
+		return err
+	}
+	return convertToExternalPluginConfigArgs(out)
+}
+
+// convertToExternalPluginConfigArgs converts PluginConfig#Args into
+// external (versioned) types using a scheme.
+func convertToExternalPluginConfigArgs(out *DeschedulerPolicy) error {
+	scheme := GetPluginArgConversionScheme()
+	for i := range out.Profiles {
+		for j := range out.Profiles[i].PluginConfigs {
+			args := out.Profiles[i].PluginConfigs[j].Args
+			if args.Object == nil {
+				continue
+			}
+			if _, isUnknown := args.Object.(*runtime.Unknown); isUnknown {
+				continue
+			}
+			externalArgs, err := scheme.ConvertToVersion(args.Object, SchemeGroupVersion)
+			if err != nil {
+				return err
+			}
+			out.Profiles[i].PluginConfigs[j].Args.Object = externalArgs
+		}
+	}
+	return nil
+}