MM-10702 Moving plugins to use hashicorp go-plugin. (#8978)

* Moving plugins to use hashicorp go-plugin.

* Tweaks from feedback.

1 files changed, 377 insertions, 0 deletions

diff --git a/plugin/interface_generator/main.go b/plugin/interface_generator/main.go
new file mode 100644
index 000000000..5f66506d3
--- /dev/null
+++ b/plugin/interface_generator/main.go
@@ -0,0 +1,377 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/alecthomas/template"
+	"github.com/pkg/errors"
+)
+
+type IHookEntry struct {
+	FuncName string
+	Args     *ast.FieldList
+	Results  *ast.FieldList
+}
+
+type PluginInterfaceInfo struct {
+	Hooks   []IHookEntry
+	API     []IHookEntry
+	FileSet *token.FileSet
+}
+
+func FieldListToFuncList(fieldList *ast.FieldList, fileset *token.FileSet) string {
+	result := []string{}
+	if fieldList == nil || len(fieldList.List) == 0 {
+		return "()"
+	}
+	for _, field := range fieldList.List {
+		typeNameBuffer := &bytes.Buffer{}
+		err := printer.Fprint(typeNameBuffer, fileset, field.Type)
+		if err != nil {
+			panic(err)
+		}
+		typeName := typeNameBuffer.String()
+		names := []string{}
+		for _, name := range field.Names {
+			names = append(names, name.Name)
+		}
+		result = append(result, strings.Join(names, ", ")+" "+typeName)
+	}
+
+	return "(" + strings.Join(result, ", ") + ")"
+}
+
+func FieldListToNames(fieldList *ast.FieldList, fileset *token.FileSet) string {
+	result := []string{}
+	if fieldList == nil || len(fieldList.List) == 0 {
+		return ""
+	}
+	for _, field := range fieldList.List {
+		for _, name := range field.Names {
+			result = append(result, name.Name)
+		}
+	}
+
+	return strings.Join(result, ", ")
+}
+
+func FieldListDestruct(structPrefix string, fieldList *ast.FieldList, fileset *token.FileSet) string {
+	result := []string{}
+	if fieldList == nil || len(fieldList.List) == 0 {
+		return ""
+	}
+	nextLetter := 'A'
+	for _, field := range fieldList.List {
+		if len(field.Names) == 0 {
+			result = append(result, structPrefix+string(nextLetter))
+			nextLetter += 1
+		} else {
+			for range field.Names {
+				result = append(result, structPrefix+string(nextLetter))
+				nextLetter += 1
+			}
+		}
+	}
+
+	return strings.Join(result, ", ")
+}
+
+func FieldListToStructList(fieldList *ast.FieldList, fileset *token.FileSet) string {
+	result := []string{}
+	if fieldList == nil || len(fieldList.List) == 0 {
+		return ""
+	}
+	nextLetter := 'A'
+	for _, field := range fieldList.List {
+		typeNameBuffer := &bytes.Buffer{}
+		err := printer.Fprint(typeNameBuffer, fileset, field.Type)
+		if err != nil {
+			panic(err)
+		}
+		typeName := typeNameBuffer.String()
+		if len(field.Names) == 0 {
+			result = append(result, string(nextLetter)+" "+typeName)
+			nextLetter += 1
+		} else {
+			for range field.Names {
+				result = append(result, string(nextLetter)+" "+typeName)
+				nextLetter += 1
+			}
+		}
+	}
+
+	return strings.Join(result, "\n\t")
+}
+
+func goList(dir string) ([]string, error) {
+	cmd := exec.Command("go", "list", "-f", "{{.Dir}}", dir)
+	bytes, err := cmd.Output()
+	if err != nil {
+		return nil, errors.Wrap(err, "Can't list packages")
+	}
+
+	return strings.Fields(string(bytes)), nil
+}
+
+func (info *PluginInterfaceInfo) addHookMethod(method *ast.Field) {
+	info.Hooks = append(info.Hooks, IHookEntry{
+		FuncName: method.Names[0].Name,
+		Args:     method.Type.(*ast.FuncType).Params,
+		Results:  method.Type.(*ast.FuncType).Results,
+	})
+}
+
+func (info *PluginInterfaceInfo) addAPIMethod(method *ast.Field) {
+	info.API = append(info.API, IHookEntry{
+		FuncName: method.Names[0].Name,
+		Args:     method.Type.(*ast.FuncType).Params,
+		Results:  method.Type.(*ast.FuncType).Results,
+	})
+}
+
+func (info *PluginInterfaceInfo) makeHookInspector() func(node ast.Node) bool {
+	return func(node ast.Node) bool {
+		if typeSpec, ok := node.(*ast.TypeSpec); ok {
+			if typeSpec.Name.Name == "Hooks" {
+				for _, method := range typeSpec.Type.(*ast.InterfaceType).Methods.List {
+					info.addHookMethod(method)
+				}
+				return false
+			} else if typeSpec.Name.Name == "API" {
+				for _, method := range typeSpec.Type.(*ast.InterfaceType).Methods.List {
+					info.addAPIMethod(method)
+				}
+				return false
+			}
+		}
+		return true
+	}
+}
+
+func getPluginInfo(dir string) (*PluginInterfaceInfo, error) {
+	pluginInfo := &PluginInterfaceInfo{
+		Hooks:   make([]IHookEntry, 0),
+		FileSet: token.NewFileSet(),
+	}
+
+	packages, err := parser.ParseDir(pluginInfo.FileSet, dir, nil, parser.ParseComments)
+	if err != nil {
+		log.Println("Parser error in dir "+dir+": ", err)
+	}
+
+	for _, pkg := range packages {
+		if pkg.Name != "plugin" {
+			continue
+		}
+
+		for _, file := range pkg.Files {
+			ast.Inspect(file, pluginInfo.makeHookInspector())
+		}
+	}
+
+	return pluginInfo, nil
+}
+
+var hooksTemplate = `// 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}}
+
+func init() {
+	HookNameToId["{{.Name}}"] = {{.Name}}Id
+}
+
+type {{.Name}}Args struct {
+	{{structStyle .Params}}
+}
+
+type {{.Name}}Returns struct {
+	{{structStyle .Return}}
+}
+
+func (g *HooksRPCClient) {{.Name}}{{funcStyle .Params}} {{funcStyle .Return}} {
+	_args := &{{.Name}}Args{ {{valuesOnly .Params}} }
+	_returns := &{{.Name}}Returns{}
+	if g.implemented[{{.Name}}Id] {
+		if err := g.client.Call("Plugin.{{.Name}}", _args, _returns); err != nil {
+			g.log.Error("RPC call {{.Name}} to plugin failed.", mlog.Err(err))
+		}
+	}
+	return {{destruct "_returns." .Return}}
+}
+
+func (s *HooksRPCServer) {{.Name}}(args *{{.Name}}Args, returns *{{.Name}}Returns) error {
+	if hook, ok := s.impl.(interface {
+		{{.Name}}{{funcStyle .Params}} {{funcStyle .Return}}
+	}); ok {
+		{{if .Return}}{{destruct "returns." .Return}} = {{end}}hook.{{.Name}}({{destruct "args." .Params}})
+	}
+	return nil
+}
+{{end}}
+
+{{range .APIMethods}}
+
+type {{.Name}}Args struct {
+	{{structStyle .Params}}
+}
+
+type {{.Name}}Returns struct {
+	{{structStyle .Return}}
+}
+
+func (g *APIRPCClient) {{.Name}}{{funcStyle .Params}} {{funcStyle .Return}} {
+	_args := &{{.Name}}Args{ {{valuesOnly .Params}} }
+	_returns := &{{.Name}}Returns{}
+	if err := g.client.Call("Plugin.{{.Name}}", _args, _returns); err != nil {
+		g.log.Error("RPC call to {{.Name}} API failed.", mlog.Err(err))
+	}
+	return {{destruct "_returns." .Return}}
+}
+
+func (s *APIRPCServer) {{.Name}}(args *{{.Name}}Args, returns *{{.Name}}Returns) error {
+	if hook, ok := s.impl.(interface {
+		{{.Name}}{{funcStyle .Params}} {{funcStyle .Return}}
+	}); ok {
+		{{if .Return}}{{destruct "returns." .Return}} = {{end}}hook.{{.Name}}({{destruct "args." .Params}})
+	}
+	return nil
+}
+{{end}}
+`
+
+type MethodParams struct {
+	Name   string
+	Params *ast.FieldList
+	Return *ast.FieldList
+}
+
+type HooksTemplateParams struct {
+	HooksMethods []MethodParams
+	APIMethods   []MethodParams
+}
+
+func generateGlue(info *PluginInterfaceInfo) {
+	templateFunctions := map[string]interface{}{
+		"funcStyle":   func(fields *ast.FieldList) string { return FieldListToFuncList(fields, info.FileSet) },
+		"structStyle": func(fields *ast.FieldList) string { return FieldListToStructList(fields, info.FileSet) },
+		"valuesOnly":  func(fields *ast.FieldList) string { return FieldListToNames(fields, info.FileSet) },
+		"destruct": func(structPrefix string, fields *ast.FieldList) string {
+			return FieldListDestruct(structPrefix, fields, info.FileSet)
+		},
+	}
+
+	hooksTemplate, err := template.New("hooks").Funcs(templateFunctions).Parse(hooksTemplate)
+	if err != nil {
+		panic(err)
+	}
+
+	templateParams := HooksTemplateParams{}
+	for _, hook := range info.Hooks {
+		templateParams.HooksMethods = append(templateParams.HooksMethods, MethodParams{
+			Name:   hook.FuncName,
+			Params: hook.Args,
+			Return: hook.Results,
+		})
+	}
+	for _, api := range info.API {
+		templateParams.APIMethods = append(templateParams.APIMethods, MethodParams{
+			Name:   api.FuncName,
+			Params: api.Args,
+			Return: api.Results,
+		})
+	}
+	templateResult := &bytes.Buffer{}
+	hooksTemplate.Execute(templateResult, &templateParams)
+
+	importsBuffer := &bytes.Buffer{}
+	cmd := exec.Command("goimports")
+	cmd.Stdin = templateResult
+	cmd.Stdout = importsBuffer
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		panic(err)
+	}
+
+	if err := ioutil.WriteFile(filepath.Join(getPluginPackageDir(), "client_rpc_generated.go"), importsBuffer.Bytes(), 0664); err != nil {
+		panic(err)
+	}
+}
+
+func getPluginPackageDir() string {
+	dirs, err := goList("github.com/mattermost/mattermost-server/plugin")
+	if err != nil {
+		panic(err)
+	} else if len(dirs) != 1 {
+		panic("More than one package dir, or no dirs!")
+	}
+
+	return dirs[0]
+}
+
+func removeExcluded(info *PluginInterfaceInfo) *PluginInterfaceInfo {
+	toBeExcluded := func(item string) bool {
+		excluded := []string{
+			"OnActivate",
+			"Implemented",
+			"LoadPluginConfiguration",
+			"ServeHTTP",
+		}
+		for _, exclusion := range excluded {
+			if exclusion == item {
+				return true
+			}
+		}
+		return false
+	}
+	hooksResult := make([]IHookEntry, 0, len(info.Hooks))
+	for _, hook := range info.Hooks {
+		if !toBeExcluded(hook.FuncName) {
+			hooksResult = append(hooksResult, hook)
+		}
+	}
+	info.Hooks = hooksResult
+
+	apiResult := make([]IHookEntry, 0, len(info.API))
+	for _, api := range info.API {
+		if !toBeExcluded(api.FuncName) {
+			apiResult = append(apiResult, api)
+		}
+	}
+	info.API = apiResult
+
+	return info
+}
+
+func main() {
+	pluginPackageDir := getPluginPackageDir()
+
+	log.Println("Generating plugin glue")
+	info, err := getPluginInfo(pluginPackageDir)
+	if err != nil {
+		fmt.Println("Unable to get plugin info: " + err.Error())
+	}
+
+	info = removeExcluded(info)
+
+	generateGlue(info)
+}