plugin/product: improve product hooks API (#20556)

* plugin/product: improve product hooks API

* elaborate HookService.RegisterHooks method documentation

* remove unnecessary re-assigns

plugin/interface_generator/main.go

@@ -21,6 +21,29 @@ import (
 	"golang.org/x/tools/imports"
 )
 
+var excludedPluginHooks = []string{
+	"FileWillBeUploaded",
+	"Implemented",
+	"LoadPluginConfiguration",
+	"InstallPlugin",
+	"LogDebug",
+	"LogError",
+	"LogInfo",
+	"LogWarn",
+	"MessageWillBePosted",
+	"MessageWillBeUpdated",
+	"OnActivate",
+	"PluginHTTP",
+	"ServeHTTP",
+}
+
+var excludedProductHooks = []string{
+	"Implemented",
+	"OnActivate",
+	"OnDeactivate",
+	"ServeHTTP",
+}
+
 type IHookEntry struct {
 	FuncName string
 	Args     *ast.FieldList
@@ -360,6 +383,61 @@ func (s *apiRPCServer) {{.Name}}(args *{{.Name | obscure}}Args, returns *{{.Name
 {{end}}
 `
 
+var productHooksTemplate = `// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// Code generated by "make pluginapi"
+// DO NOT EDIT
+
+package plugin
+
+{{range .HooksMethods}}
+type {{.Name}}IFace interface {
+	{{.Name}}{{funcStyle .Params}} {{funcStyle .Return}}
+}
+
+{{end}}
+
+type hooksAdapter struct {
+	implemented  map[int]struct{}
+	productHooks any
+}
+
+func newAdapter(productHooks any) (*hooksAdapter, error) {
+	a := &hooksAdapter{
+		implemented:  make(map[int]struct{}),
+	}
+	var tt reflect.Type
+	ft := reflect.TypeOf(productHooks)
+	{{range .HooksMethods}}
+	// Assessing the type of the productHooks if it individually implements {{.Name}} interface.
+	tt = reflect.TypeOf((*{{.Name}}IFace)(nil)).Elem()
+
+    if ft.Implements(tt) {
+		a.implemented[{{.Name}}ID] = struct{}{}
+	} else if _, ok := ft.MethodByName("{{.Name}}"); ok{
+		return nil, errors.New("hook has {{.Name}} method but does not implement plugin.{{.Name}} interface")
+	}
+
+	{{end}}
+
+	return a, nil
+}
+
+{{range .HooksMethods}}
+func (a *hooksAdapter) {{.Name}}{{funcStyle .Params}} {{funcStyle .Return}} {
+	if _, ok := a.implemented[{{.Name}}ID]; !ok {
+		panic("product hooks must implement {{.Name}}")
+	}
+
+	{{if .Return}}return a.productHooks.({{.Name}}IFace).{{.Name}}({{valuesOnly .Params}}){{else}}a.productHooks.({{.Name}}IFace).{{.Name}}({{valuesOnly .Params}}){{end}}
+
+}
+
+{{end}}
+
+`
+
 var apiTimerLayerTemplate = `// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
@@ -507,6 +585,39 @@ func generateHooksGlue(info *PluginInterfaceInfo) {
 	}
 }
 
+func generateProductHooksInterfaces(info *PluginInterfaceInfo) {
+	templateFunctions := map[string]interface{}{
+		"funcStyle":  func(fields *ast.FieldList) string { return FieldListToFuncList(fields, info.FileSet) },
+		"valuesOnly": func(fields *ast.FieldList) string { return FieldListToNames(fields, false) },
+	}
+
+	templateParams := HooksTemplateParams{}
+	for _, hook := range info.Hooks {
+		templateParams.HooksMethods = append(templateParams.HooksMethods, MethodParams{
+			Name:   hook.FuncName,
+			Params: hook.Args,
+			Return: hook.Results,
+		})
+	}
+
+	productHooksTemplate, err := template.New("hooks").Funcs(templateFunctions).Parse(productHooksTemplate)
+	if err != nil {
+		panic(err)
+	}
+
+	templateResult := &bytes.Buffer{}
+	productHooksTemplate.Execute(templateResult, &templateParams)
+
+	formatted, err := imports.Process("", templateResult.Bytes(), nil)
+	if err != nil {
+		panic(err)
+	}
+
+	if err := ioutil.WriteFile(filepath.Join(getPluginPackageDir(), "product_hooks_generated.go"), formatted, 0664); err != nil {
+		panic(err)
+	}
+}
+
 func generatePluginTimerLayer(info *PluginInterfaceInfo) {
 	templateFunctions := map[string]interface{}{
 		"funcStyle":   func(fields *ast.FieldList) string { return FieldListToFuncList(fields, info.FileSet) },
@@ -573,23 +684,11 @@ func getPluginPackageDir() string {
 	return dirs[0]
 }
 
-func removeExcluded(info *PluginInterfaceInfo) *PluginInterfaceInfo {
+func removeExcluded(info *PluginInterfaceInfo, excluded []string) *PluginInterfaceInfo {
+	newIface := &PluginInterfaceInfo{
+		FileSet: info.FileSet,
+	}
 	toBeExcluded := func(item string) bool {
-		excluded := []string{
-			"FileWillBeUploaded",
-			"Implemented",
-			"LoadPluginConfiguration",
-			"InstallPlugin",
-			"LogDebug",
-			"LogError",
-			"LogInfo",
-			"LogWarn",
-			"MessageWillBePosted",
-			"MessageWillBeUpdated",
-			"OnActivate",
-			"PluginHTTP",
-			"ServeHTTP",
-		}
 		for _, exclusion := range excluded {
 			if exclusion == item {
 				return true
@@ -603,7 +702,7 @@ func removeExcluded(info *PluginInterfaceInfo) *PluginInterfaceInfo {
 			hooksResult = append(hooksResult, hook)
 		}
 	}
-	info.Hooks = hooksResult
+	newIface.Hooks = hooksResult
 
 	apiResult := make([]IHookEntry, 0, len(info.API))
 	for _, api := range info.API {
@@ -611,20 +710,23 @@ func removeExcluded(info *PluginInterfaceInfo) *PluginInterfaceInfo {
 			apiResult = append(apiResult, api)
 		}
 	}
-	info.API = apiResult
+	newIface.API = apiResult
 
-	return info
+	return newIface
 }
 
 func main() {
 	pluginPackageDir := getPluginPackageDir()
 
-	log.Println("Generating plugin hooks glue")
 	forRPC, err := getPluginInfo(pluginPackageDir)
 	if err != nil {
 		fmt.Println("Unable to get plugin info: " + err.Error())
 	}
-	generateHooksGlue(removeExcluded(forRPC))
+	log.Println("Generating product hooks interfaces")
+	generateProductHooksInterfaces(removeExcluded(forRPC, excludedProductHooks))
+
+	log.Println("Generating plugin hooks glue")
+	generateHooksGlue(removeExcluded(forRPC, excludedPluginHooks))
 
 	// Generate plugin timer layers
 	log.Println("Generating plugin timer glue")