fix: ignore protobuf files without messages when generating code

cmd/protoc-gen-fastmarshal/funcs.go

@@ -198,7 +198,6 @@ func addSprigFunctions(fm template.FuncMap) template.FuncMap {
 func addProtoFunctions(fm template.FuncMap, protoFile *protogen.File, names specialNames, goPackageForFile map[string]string) template.FuncMap {
 	fm["protoNumberEncodeMethod"] = protoNumberEncodeMethod
 	fm["getExtensions"] = getExtensions(protoFile)
-	fm["allMessages"] = allMessages(protoFile)
 	fm["getAdditionalImports"] = getAdditionalImports(protoFile, goPackageForFile)
 	fm["getImportPrefix"] = getImportPrefix(protoFile, goPackageForFile)
 	fm["mapFieldGoType"] = mapFieldGoType(protoFile, goPackageForFile)
@@ -250,28 +249,6 @@ func getExtensions(protoFile *protogen.File) func(*protogen.Message) []*protogen
 	}
 }
 
-// allMessages returns a list of all top-level and nested message definitions in protoFile
-func allMessages(protoFile *protogen.File) func() []*protogen.Message {
-	var queue, msgs []*protogen.Message
-	queue = append(queue, protoFile.Messages...)
-	for len(queue) > 0 {
-		m := queue[0]
-		queue = queue[1:]
-		msgs = append(msgs, m)
-		for _, mm := range m.Messages {
-			// skip "messgaes" that represent map fields
-			if mm.Desc.IsMapEntry() {
-				continue
-			}
-			queue = append(queue, mm)
-		}
-	}
-
-	return func() []*protogen.Message {
-		return msgs
-	}
-}
-
 // getAdditionalImports returns a set of distinct imports paths required by the fields of v, which
 // must be either a single protogen.Message or a slice of messages.
 //
@@ -440,7 +417,7 @@ func msgHasRequiredField(m *protogen.Message) bool {
 func hasRequiredFields(protoFile *protogen.File) func(*protogen.Message) bool {
 	anyMessageHasRequiredFields := false
 	if protoFile.Desc.Syntax() == protoreflect.Proto2 {
-		for _, m := range allMessages(protoFile)() {
+		for _, m := range allMessages(protoFile) {
 			anyMessageHasRequiredFields = anyMessageHasRequiredFields || msgHasRequiredField(m)
 		}
 	}

cmd/protoc-gen-fastmarshal/generate_request.go

@@ -23,6 +23,7 @@ const (
 // Protobuf code generator
 type generateRequest struct {
 	ProtoDesc          *protogen.File
+	Messages           []*protogen.Message
 	Mode               outputMode
 	NameTemplate       string
 	Funcs              template.FuncMap

cmd/protoc-gen-fastmarshal/generator.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"maps"
 	"os"
 	"time"
 
@@ -21,6 +22,7 @@ func generateSingle(plugin *protogen.Plugin, req generateRequest) error {
 		Now                time.Time
 		Pwd                string
 		ProtoDesc          *protogen.File
+		Messages           []*protogen.Message
 		APIVersion         string
 		SpecialNames       specialNames
 		EnableUnsafeDecode bool
@@ -29,6 +31,7 @@ func generateSingle(plugin *protogen.Plugin, req generateRequest) error {
 		Now:                time.Now().UTC(),
 		Pwd:                func() string { p, _ := os.Getwd(); return p }(),
 		ProtoDesc:          req.ProtoDesc,
+		Messages:           req.Messages,
 		APIVersion:         req.APIVersion,
 		SpecialNames:       req.SpecialNames,
 		EnableUnsafeDecode: req.EnableUnsafeDecode,
@@ -38,26 +41,29 @@ func generateSingle(plugin *protogen.Plugin, req generateRequest) error {
 		name, content string
 		err           error
 	)
+
 	goPackageForFile := make(map[string]string, len(plugin.Files))
 	for _, f := range plugin.Files {
 		goPackageForFile[f.Desc.Path()] = string(f.GoPackageName)
 	}
 	funcs := codeGenFunctions(req.ProtoDesc, req.SpecialNames, goPackageForFile)
-	for k, v := range req.Funcs {
-		funcs[k] = v
-	}
+	maps.Copy(funcs, req.Funcs)
+
 	nt, err := loadTemplateFromString(req.NameTemplate, funcs)
 	if err != nil {
 		return fmt.Errorf("unable to parse output file name template: %w", err)
 	}
+
 	name, err = renderTemplate(nt, args)
 	if err != nil {
 		return fmt.Errorf("unable to generate output file name from name template: %w", err)
 	}
+
 	ct, err := loadTemplateFromEmbedded(funcs)
 	if err != nil {
 		return fmt.Errorf("unable to load embedded content templates: %w", err)
 	}
+
 	content, err = renderNamedTemplate(ct, "SingleFile", args)
 	if err != nil {
 		return fmt.Errorf("unable to generate output from content template: %w", err)
@@ -86,9 +92,7 @@ func generatePerMessage(plugin *protogen.Plugin, req generateRequest) error {
 		goPackageForFile[f.Desc.Path()] = string(f.GoPackageName)
 	}
 	funcs := codeGenFunctions(req.ProtoDesc, req.SpecialNames, goPackageForFile)
-	for k, v := range req.Funcs {
-		funcs[k] = v
-	}
+	maps.Copy(funcs, req.Funcs)
 
 	var (
 		now    = time.Now().UTC()
@@ -99,7 +103,7 @@ func generatePerMessage(plugin *protogen.Plugin, req generateRequest) error {
 	if err != nil {
 		return fmt.Errorf("unable to load embedded content templates: %w", err)
 	}
-	for _, msg := range allMessages(req.ProtoDesc)() {
+	for _, msg := range req.Messages {
 		args := genArgsPerFile{
 			Now:                now,
 			Pwd:                pwd,
@@ -109,6 +113,7 @@ func generatePerMessage(plugin *protogen.Plugin, req generateRequest) error {
 			SpecialNames:       req.SpecialNames,
 			EnableUnsafeDecode: req.EnableUnsafeDecode,
 		}
+
 		content, err := renderNamedTemplate(tt, "PerMessage", args)
 		if err != nil {
 			return fmt.Errorf("error executing content template for message %s: %w", msg.Desc.FullName(), err)

cmd/protoc-gen-fastmarshal/run.go

@@ -128,6 +128,11 @@ func doGenerate(opts *options) func(*protogen.Plugin) error {
 				continue
 			}
 
+			messages := allMessages(protoFile)
+			if len(messages) == 0 {
+				continue
+			}
+
 			// account for per-message output mode
 			// - default output template is "[protofile].pb.fm.go"
 			// - file-per-message template is "[protofile]_[lower(messagename)].pb.fm.go"
@@ -139,6 +144,7 @@ func doGenerate(opts *options) func(*protogen.Plugin) error {
 			req := generateRequest{
 				Mode:               outputModeSingleFile,
 				ProtoDesc:          protoFile,
+				Messages:           messages,
 				NameTemplate:       nameTemplate,
 				APIVersion:         opts.apiVersion.String(),
 				SpecialNames:       opts.specialNames,
@@ -154,3 +160,22 @@ func doGenerate(opts *options) func(*protogen.Plugin) error {
 		return nil
 	}
 }
+
+// allMessages returns a list of all top-level and nested message definitions in protoFile
+func allMessages(protoFile *protogen.File) []*protogen.Message {
+	var queue, msgs []*protogen.Message
+	queue = append(queue, protoFile.Messages...)
+	for len(queue) > 0 {
+		m := queue[0]
+		queue = queue[1:]
+		msgs = append(msgs, m)
+		for _, mm := range m.Messages {
+			// skip "messages" that represent map fields
+			if mm.Desc.IsMapEntry() {
+				continue
+			}
+			queue = append(queue, mm)
+		}
+	}
+	return msgs
+}

cmd/protoc-gen-fastmarshal/run_test.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"flag"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/compiler/protogen"
+	"google.golang.org/protobuf/types/descriptorpb"
+	"google.golang.org/protobuf/types/pluginpb"
+
+	"github.com/CrowdStrike/csproto"
+)
+
+func Test_doGenerate_Empty(t *testing.T) {
+	flags := flag.NewFlagSet("", flag.PanicOnError)
+	pluginOpts := protogen.Options{ParamFunc: flags.Set}
+
+	plugin, err := pluginOpts.New(&pluginpb.CodeGeneratorRequest{
+		FileToGenerate: []string{"empty.proto"},
+		ProtoFile: []*descriptorpb.FileDescriptorProto{
+			{
+				Name:    csproto.String("empty.proto"),
+				Package: csproto.String("crowdstrike.csproto.test"),
+				Syntax:  csproto.String("proto3"),
+				Options: &descriptorpb.FileOptions{
+					GoPackage: csproto.String("github.com/CrowdStrike/csproto/testpb"),
+				},
+			},
+		},
+	})
+	require.NoError(t, err)
+
+	runPlugin := doGenerate(&options{
+		specialNames: make(specialNames),
+	})
+
+	err = runPlugin(plugin)
+	require.NoError(t, err)
+
+	resp := plugin.Response()
+	require.Empty(t, resp.File)
+}

cmd/protoc-gen-fastmarshal/templates/permessage.go.tmpl

@@ -189,4 +189,4 @@ func (m *{{.Message.GoIdent.GoName}}) csprotoCheckRequiredFields() error {
     return nil
 }
 {{ end }}
-{{end}}
+{{end}}

cmd/protoc-gen-fastmarshal/templates/singlefile.go.tmpl

@@ -12,11 +12,11 @@ import (
     "strings"{{end}}
     "sync/atomic"
     "github.com/CrowdStrike/csproto"
-    {{range $path, $alias := (allMessages | getAdditionalImports)}}{{ (printf "%s %s" $alias $path) | trimspace}}
+    {{range $path, $alias := (.Messages | getAdditionalImports)}}{{ (printf "%s %s" $alias $path) | trimspace}}
     {{end}}
 )
 
-{{ range allMessages }}
+{{ range .Messages }}
 
 //------------------------------------------------------------------------------
 // Custom Protobuf size/marshal/unmarshal code for {{ .GoIdent.GoName }}
@@ -192,4 +192,4 @@ func (m *{{.GoIdent.GoName}}) csprotoCheckRequiredFields() error {
 }
 {{ end }}
 {{ end }}
-{{end}}
+{{end}}