[GitHub] [dubbo-go] xavier-niu commented on a change in pull request #1370: Ftr: Add config loader hooks for 3.0

[GitBox <gi...@apache.org>]

xavier-niu commented on a change in pull request #1370:
URL: https://github.com/apache/dubbo-go/pull/1370#discussion_r692633485



##########
File path: config/config_loader_hook.go
##########
@@ -0,0 +1,367 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 config
+
+import (
+	"fmt"
+	"reflect"
+)
+
+import (
+	"dubbo.apache.org/dubbo-go/v3/common/constant"
+)
+
+const (
+	hookParams = constant.HookParams
+)
+
+type LoaderHook interface {
+	emit() bool
+	// if you want to use emitWithParams, you must add HookParams field and make emit return false
+	emitWithParams(params interface{}) bool
+}
+
+func getLoaderHookType(t LoaderHook) reflect.Type {
+	hookType := reflect.TypeOf(t)
+	if reflect.Ptr == hookType.Kind() {
+		hookType = hookType.Elem()
+	}
+	return hookType
+}
+
+func getLoaderHookTypeString(t LoaderHook) string {
+	return getLoaderHookType(t).String()
+}
+
+func getLoaderHookInfo(v reflect.Value) reflect.Value {
+	if reflect.Ptr == v.Kind() {
+		v = v.Elem()
+	}
+	return v
+}
+
+func getLoaderHookParams(t LoaderHook) interface{} {
+	hookType := getLoaderHookType(t)
+	_, existed := hookType.FieldByName(hookParams)
+	if !existed {
+		panic(fmt.Sprintf("Hook field [%s] not existed for %s", hookParams, hookType.Name()))
+	}
+	hookParams := getLoaderHookInfo(reflect.ValueOf(t)).FieldByName(hookParams)
+	return getLoaderHookInfo(hookParams).Interface()
+}
+
+func AddLoaderHooks(hooks ...LoaderHook) {
+	if len(hooks) > 0 {
+		if loaderHooks == nil {
+			loaderHooks = map[string][]LoaderHook{}
+		}
+		for _, hook := range hooks {
+			hookType := getLoaderHookTypeString(hook)
+			var hooks []LoaderHook
+			if hs, ok := loaderHooks[hookType]; ok {
+				hooks = hs
+			}
+			if hooks == nil {
+				hooks = []LoaderHook{}
+			}
+			loaderHooks[hookType] = append(hooks, hook)
+		}

Review comment:
       It seems that `hooks` is a useless variable in this case.
   
   ```go
   if _, ok := loaderHooks[hookType]; !ok {
      loaderHooks[hookType] = make([]LoaderHook)
   }
   loaderHooks[hookType] = append(loaderHooks[hookType], hook)
   ```




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