make templates self-contained and pluginable

module/BUILD

@@ -10,6 +10,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//templates",
+        "//templates/shared",
         "//templates/java",
         "//validate",
         "@com_github_lyft_protoc_gen_star//:protoc-gen-star",

module/validate.go

@@ -1,17 +1,20 @@
 package module
 
 import (
+	"strings"
+
 	"github.com/envoyproxy/protoc-gen-validate/templates"
 	"github.com/envoyproxy/protoc-gen-validate/templates/java"
+	"github.com/envoyproxy/protoc-gen-validate/templates/shared"
 	pgs "github.com/lyft/protoc-gen-star"
 	pgsgo "github.com/lyft/protoc-gen-star/lang/go"
-	"strings"
 )
 
 const (
-	validatorName = "validator"
-	langParam     = "lang"
-	moduleParam   = "module"
+	validatorName   = "validator"
+	langParam       = "lang"
+	langPluginParam = "lang-plugin"
+	moduleParam     = "module"
 )
 
 type Module struct {
@@ -29,13 +32,8 @@ func (m *Module) InitContext(ctx pgs.BuildContext) {
 func (m *Module) Name() string { return validatorName }
 
 func (m *Module) Execute(targets map[string]pgs.File, pkgs map[string]pgs.Package) []pgs.Artifact {
-	lang := m.Parameters().Str(langParam)
-	m.Assert(lang != "", "`lang` parameter must be set")
 	module := m.Parameters().Str(moduleParam)
-
-	// Process file-level templates
-	tpls := templates.Template(m.Parameters())[lang]
-	m.Assert(tpls != nil, "could not find templates for `lang`: ", lang)
+	plugin := m.resolveTemplate()
 
 	for _, f := range targets {
 		m.Push(f.Name().String())
@@ -44,16 +42,16 @@ func (m *Module) Execute(targets map[string]pgs.File, pkgs map[string]pgs.Packag
 			m.CheckRules(msg)
 		}
 
-		for _, tpl := range tpls {
-			out := templates.FilePathFor(tpl)(f, m.ctx, tpl)
+		for _, tpl := range plugin.Templates {
+			out := plugin.PathFunction(f, m.ctx, tpl)
 
 			// A nil path means no output should be generated for this file - as controlled by
 			// implementation-specific FilePathFor implementations.
 			// Ex: Don't generate Java validators for files that don't reference PGV.
 			if out != nil {
 				outPath := strings.TrimLeft(strings.ReplaceAll(out.String(), module, ""), "/")
 
-				if opts := f.Descriptor().GetOptions(); opts != nil && opts.GetJavaMultipleFiles() && lang == "java" {
+				if opts := f.Descriptor().GetOptions(); opts != nil && opts.GetJavaMultipleFiles() && plugin.Name == "java" {
 					// TODO: Only Java supports multiple file generation. If more languages add multiple file generation
 					// support, the implementation should be made more inderect.
 					for _, msg := range f.Messages() {
@@ -71,4 +69,20 @@ func (m *Module) Execute(targets map[string]pgs.File, pkgs map[string]pgs.Packag
 	return m.Artifacts()
 }
 
+func (m *Module) resolveTemplate() *shared.TemplatePlugin {
+	lang := m.Parameters().Str(langParam)
+	langPlugin := m.Parameters().Str(langPluginParam)
+	m.Assert(lang != "" || langPlugin != "", "`lang` parameter or `lang-plugin` must be set")
+
+	if lang != "" {
+		plugin := templates.MakeTemplateForLang(m.Parameters(), lang)
+		m.Assert(plugin != nil, "could not find templates for `lang`: ", lang)
+		return plugin
+	}
+
+	plugin, err := templates.MakeTemplateFromPlugin(langPlugin, m.Parameters())
+	m.Assert(err == nil, err)
+	return plugin
+}
+
 var _ pgs.Module = (*Module)(nil)

templates/cc/BUILD.bazel

@@ -17,6 +17,7 @@ go_library(
         "msg.go",
         "none.go",
         "num.go",
+        "plugin.go",
         "register.go",
         "repeated.go",
         "string.go",

templates/cc/plugin.go

@@ -0,0 +1,21 @@
+package cc
+
+import (
+	"text/template"
+
+	"github.com/envoyproxy/protoc-gen-validate/templates/shared"
+	pgs "github.com/lyft/protoc-gen-star"
+)
+
+const PluginName = "cc"
+
+func MakePlugin(params pgs.Parameters) *shared.TemplatePlugin {
+	return &shared.TemplatePlugin{
+		Templates: []*template.Template{
+			shared.MakeTemplate("h", registerHeader, params),
+			shared.MakeTemplate("cc", registerModule, params),
+		},
+		PathFunction: ccFilePath,
+		Name:         PluginName,
+	}
+}

templates/cc/register.go

@@ -15,7 +15,7 @@ import (
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
-func RegisterModule(tpl *template.Template, params pgs.Parameters) {
+func registerModule(tpl *template.Template, params pgs.Parameters) {
 	fns := CCFuncs{pgsgo.InitContext(params)}
 
 	tpl.Funcs(map[string]interface{}{
@@ -91,7 +91,7 @@ func RegisterModule(tpl *template.Template, params pgs.Parameters) {
 	template.Must(tpl.New("wrapper").Parse(wrapperTpl))
 }
 
-func RegisterHeader(tpl *template.Template, params pgs.Parameters) {
+func registerHeader(tpl *template.Template, params pgs.Parameters) {
 	fns := CCFuncs{pgsgo.InitContext(params)}
 
 	tpl.Funcs(map[string]interface{}{
@@ -107,7 +107,7 @@ func RegisterHeader(tpl *template.Template, params pgs.Parameters) {
 // TODO(rodaine): break pgsgo dependency here (with equivalent pgscc subpackage)
 type CCFuncs struct{ pgsgo.Context }
 
-func CcFilePath(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath {
+func ccFilePath(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath {
 	out := pgs.FilePath(f.Name().String())
 	out = out.SetExt(".pb.validate." + tpl.Name())
 	return &out

templates/go/BUILD.bazel

@@ -6,15 +6,18 @@ go_library(
         "duration.go",
         "file.go",
         "message.go",
+        "plugin.go",
         "register.go",
         "required.go",
         "timestamp.go",
     ],
     importpath = "github.com/envoyproxy/protoc-gen-validate/templates/go",
     visibility = ["//visibility:public"],
     deps = [
+        "//templates/shared",
         "//templates/goshared",
         "@com_github_lyft_protoc_gen_star//:protoc-gen-star",
+        "@com_github_lyft_protoc_gen_star//lang/go",
     ],
 )
 

templates/go/plugin.go

@@ -0,0 +1,23 @@
+package golang
+
+import (
+	"text/template"
+
+	"github.com/envoyproxy/protoc-gen-validate/templates/shared"
+	pgs "github.com/lyft/protoc-gen-star"
+	pgsgo "github.com/lyft/protoc-gen-star/lang/go"
+)
+
+const PluginName = "go"
+
+func MakePlugin(params pgs.Parameters) *shared.TemplatePlugin {
+	return &shared.TemplatePlugin{
+		Templates: []*template.Template{shared.MakeTemplate("go", register, params)},
+		PathFunction: func(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath {
+			out := ctx.OutputPath(f)
+			out = out.SetExt(".validate." + tpl.Name())
+			return &out
+		},
+		Name: PluginName,
+	}
+}

templates/go/register.go

@@ -3,11 +3,11 @@ package golang
 import (
 	"text/template"
 
-	"github.com/lyft/protoc-gen-star"
 	"github.com/envoyproxy/protoc-gen-validate/templates/goshared"
+	pgs "github.com/lyft/protoc-gen-star"
 )
 
-func Register(tpl *template.Template, params pgs.Parameters) {
+func register(tpl *template.Template, params pgs.Parameters) {
 	goshared.Register(tpl, params)
 	template.Must(tpl.Parse(fileTpl))
 	template.Must(tpl.New("required").Parse(requiredTpl))

templates/java/BUILD.bazel

@@ -15,6 +15,7 @@ go_library(
         "none.go",
         "num.go",
         "oneof.go",
+        "plugin.go",
         "register.go",
         "repeated.go",
         "required.go",

templates/java/plugin.go

@@ -0,0 +1,18 @@
+package java
+
+import (
+	"text/template"
+
+	"github.com/envoyproxy/protoc-gen-validate/templates/shared"
+	pgs "github.com/lyft/protoc-gen-star"
+)
+
+const PluginName = "java"
+
+func MakePlugin(params pgs.Parameters) *shared.TemplatePlugin {
+	return &shared.TemplatePlugin{
+		Templates:    []*template.Template{shared.MakeTemplate("java", register, params)},
+		PathFunction: javaFilePath,
+		Name:         PluginName,
+	}
+}

templates/java/register.go

@@ -16,7 +16,7 @@ import (
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
-func RegisterIndex(tpl *template.Template, params pgs.Parameters) {
+func registerIndex(tpl *template.Template, params pgs.Parameters) {
 	fns := javaFuncs{pgsgo.InitContext(params)}
 
 	tpl.Funcs(map[string]interface{}{
@@ -28,7 +28,7 @@ func RegisterIndex(tpl *template.Template, params pgs.Parameters) {
 	})
 }
 
-func Register(tpl *template.Template, params pgs.Parameters) {
+func register(tpl *template.Template, params pgs.Parameters) {
 	fns := javaFuncs{pgsgo.InitContext(params)}
 
 	tpl.Funcs(map[string]interface{}{
@@ -117,7 +117,7 @@ func Register(tpl *template.Template, params pgs.Parameters) {
 
 type javaFuncs struct{ pgsgo.Context }
 
-func JavaFilePath(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath {
+func javaFilePath(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath {
 	// Don't generate validators for files that don't import PGV
 	if !importsPvg(f) {
 		return nil

templates/pkg.go

@@ -1,47 +1,46 @@
 package templates
 
 import (
-	"text/template"
+	"errors"
+	"plugin"
 
-	"github.com/lyft/protoc-gen-star"
-	"github.com/lyft/protoc-gen-star/lang/go"
 	"github.com/envoyproxy/protoc-gen-validate/templates/cc"
-	"github.com/envoyproxy/protoc-gen-validate/templates/go"
+	golang "github.com/envoyproxy/protoc-gen-validate/templates/go"
 	"github.com/envoyproxy/protoc-gen-validate/templates/java"
 	"github.com/envoyproxy/protoc-gen-validate/templates/shared"
+	pgs "github.com/lyft/protoc-gen-star"
 )
 
-type RegisterFn func(tpl *template.Template, params pgs.Parameters)
-type FilePathFn func(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath
+type makePluginFn func(params pgs.Parameters) *shared.TemplatePlugin
 
-func makeTemplate(ext string, fn RegisterFn, params pgs.Parameters) *template.Template {
-	tpl := template.New(ext)
-	shared.RegisterFunctions(tpl, params)
-	fn(tpl, params)
-	return tpl
+func MakeTemplateForLang(params pgs.Parameters, lang string) *shared.TemplatePlugin {
+	switch lang {
+	case cc.PluginName:
+		return cc.MakePlugin(params)
+	case golang.PluginName:
+		return golang.MakePlugin(params)
+	case java.PluginName:
+		return java.MakePlugin(params)
+	default:
+		return nil
+	}
 }
 
-func Template(params pgs.Parameters) map[string][]*template.Template {
-	return map[string][]*template.Template{
-		"cc":   {makeTemplate("h", cc.RegisterHeader, params), makeTemplate("cc", cc.RegisterModule, params)},
-		"go":   {makeTemplate("go", golang.Register, params)},
-		"java": {makeTemplate("java", java.Register, params)},
+func MakeTemplateFromPlugin(path string, params pgs.Parameters) (*shared.TemplatePlugin, error) {
+	plug, err := plugin.Open(path)
+	if err != nil {
+		return nil, err
 	}
-}
 
-func FilePathFor(tpl *template.Template) FilePathFn {
-	switch tpl.Name() {
-	case "h":
-		return cc.CcFilePath
-	case "cc":
-		return cc.CcFilePath
-	case "java":
-		return java.JavaFilePath
-	default:
-		return func(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath {
-			out := ctx.OutputPath(f)
-			out = out.SetExt(".validate." + tpl.Name())
-			return &out
-		}
+	symPlugin, err := plug.Lookup("Plugin")
+	if err != nil {
+		return nil, err
 	}
+
+	makePlugin, ok := symPlugin.(makePluginFn)
+	if !ok {
+		return nil, errors.New("loaded object has an incorrect type, expected: *TemplatePlugin")
+	}
+
+	return makePlugin(params), nil
 }

templates/shared/BUILD.bazel

@@ -7,13 +7,15 @@ go_library(
         "disabled.go",
         "functions.go",
         "reflection.go",
+        "template.go",
         "well_known.go",
     ],
     importpath = "github.com/envoyproxy/protoc-gen-validate/templates/shared",
     visibility = ["//visibility:public"],
     deps = [
         "//validate",
         "@com_github_lyft_protoc_gen_star//:protoc-gen-star",
+        "@com_github_lyft_protoc_gen_star//lang/go",
         "@org_golang_google_protobuf//proto",
     ],
 )

templates/shared/template.go

@@ -0,0 +1,24 @@
+package shared
+
+import (
+	"text/template"
+
+	pgs "github.com/lyft/protoc-gen-star"
+	pgsgo "github.com/lyft/protoc-gen-star/lang/go"
+)
+
+type RegisterFn func(tpl *template.Template, params pgs.Parameters)
+type FilePathFn func(f pgs.File, ctx pgsgo.Context, tpl *template.Template) *pgs.FilePath
+
+type TemplatePlugin struct {
+	Templates    []*template.Template
+	PathFunction FilePathFn
+	Name         string
+}
+
+func MakeTemplate(ext string, fn RegisterFn, params pgs.Parameters) *template.Template {
+	tpl := template.New(ext)
+	RegisterFunctions(tpl, params)
+	fn(tpl, params)
+	return tpl
+}

validate/BUILD

@@ -35,6 +35,7 @@ go_proto_library(
     name = "validate_go_proto",
     importpath = "github.com/envoyproxy/protoc-gen-validate/validate",
     proto = ":validate_proto",
+    gc_goopts = ["-trimpath=$(BINDIR)=>."],
 )
 
 cc_library(