Basic testing

go.mod

@@ -2,4 +2,15 @@ module github.com/bufbuild/protoplugin
 
 go 1.21
 
-require google.golang.org/protobuf v1.32.0
+require (
+	github.com/bufbuild/protocompile v0.8.0
+	github.com/stretchr/testify v1.9.0
+	google.golang.org/protobuf v1.32.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/sync v0.5.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,6 +1,18 @@
-github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
-github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+github.com/bufbuild/protocompile v0.8.0 h1:9Kp1q6OkS9L4nM3FYbr8vlJnEwtbpDPQlQOVXfR+78s=
+github.com/bufbuild/protocompile v0.8.0/go.mod h1:+Etjg4guZoAqzVk2czwEQP12yaxLJ8DxuqCJ9qHdH94=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/sync v0.5.0 h1:60k92dhOjHxJkrqnwsfl8KuaHbn/5dl0lUPUklKo3qE=
+golang.org/x/sync v0.5.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 google.golang.org/protobuf v1.32.0 h1:pPC6BG5ex8PDFnkbrGU3EixyhKcQ2aDuBS36lqK/C7I=
 google.golang.org/protobuf v1.32.0/go.mod h1:c6P6GXX6sHbq/GpV6MGZEdwhWPcYBgnhAHhKbcUYpos=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

protoplugin.go

@@ -53,6 +53,9 @@ func Run(
 ) error {
 	// We don't use args yet, but reserving it for future use in case we want to implement automatic handling of a version flag.
 	_ = args
+	if stderr == nil {
+		stderr = io.Discard
+	}
 
 	runOptions := newRunOptions()
 	for _, option := range options {

protoplugin_test.go

@@ -0,0 +1,147 @@
+// Copyright 2024 Buf Technologies, Inc.
+//
+// Licensed 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 protoplugin
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"io/fs"
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/bufbuild/protocompile"
+	"github.com/bufbuild/protocompile/protoutil"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/descriptorpb"
+	"google.golang.org/protobuf/types/pluginpb"
+)
+
+func TestBasic(t *testing.T) {
+	t.Parallel()
+
+	testBasic(
+		t,
+		[]string{
+			"a.proto",
+		},
+		map[string][]byte{
+			"a.proto": []byte(`syntax = "proto3"; package foo; message A1 {} message A2 {}`),
+			"b.proto": []byte(`syntax = "proto3"; package foo; message B {}`),
+		},
+		HandlerFunc(
+			func(
+				ctx context.Context,
+				responseWriter *ResponseWriter,
+				request *Request,
+			) error {
+				fileDescriptorProtos, err := request.GenerateFileDescriptorProtos()
+				if err != nil {
+					return err
+				}
+				for _, fileDescriptorProto := range fileDescriptorProtos {
+					topLevelMessageNames := make([]string, len(fileDescriptorProto.GetMessageType()))
+					for i, descriptorProto := range fileDescriptorProto.GetMessageType() {
+						topLevelMessageNames[i] = descriptorProto.GetName()
+					}
+					responseWriter.AddFile(
+						fileDescriptorProto.GetName()+".txt",
+						strings.Join(topLevelMessageNames, "\n")+"\n",
+					)
+				}
+				return nil
+			},
+		),
+		map[string]string{
+			"a.proto.txt": "A1\nA2\n",
+		},
+	)
+}
+
+func testBasic(
+	t *testing.T,
+	fileToGenerate []string,
+	pathToData map[string][]byte,
+	handler Handler,
+	expectedPathToContent map[string]string,
+) {
+	ctx := context.Background()
+
+	fileDescriptorProtos, err := compile(ctx, pathToData)
+	require.NoError(t, err)
+
+	codeGeneratorRequest := &pluginpb.CodeGeneratorRequest{
+		FileToGenerate: fileToGenerate,
+		ProtoFile:      fileDescriptorProtos,
+	}
+	codeGeneratorRequestData, err := proto.Marshal(codeGeneratorRequest)
+	require.NoError(t, err)
+
+	stdin := bytes.NewReader(codeGeneratorRequestData)
+	stdout := bytes.NewBuffer(nil)
+
+	err = Run(
+		ctx,
+		nil,
+		stdin,
+		stdout,
+		nil,
+		handler,
+	)
+	require.NoError(t, err)
+
+	codeGeneratorResponse := &pluginpb.CodeGeneratorResponse{}
+	err = proto.Unmarshal(stdout.Bytes(), codeGeneratorResponse)
+	require.NoError(t, err)
+	require.Nil(t, codeGeneratorResponse.Error)
+
+	pathToContent := make(map[string]string)
+	for _, file := range codeGeneratorResponse.File {
+		require.NotEmpty(t, file.GetName())
+		pathToContent[file.GetName()] = file.GetContent()
+	}
+
+	require.Equal(t, expectedPathToContent, pathToContent)
+}
+
+func compile(ctx context.Context, pathToData map[string][]byte) ([]*descriptorpb.FileDescriptorProto, error) {
+	compiler := protocompile.Compiler{
+		Resolver: &protocompile.SourceResolver{
+			Accessor: func(path string) (io.ReadCloser, error) {
+				data, ok := pathToData[path]
+				if !ok {
+					return nil, &fs.PathError{Op: "read", Path: path, Err: fs.ErrNotExist}
+				}
+				return io.NopCloser(bytes.NewReader(data)), nil
+			},
+		},
+	}
+	paths := make([]string, 0, len(pathToData))
+	for path := range pathToData {
+		paths = append(paths, path)
+	}
+	sort.Strings(paths)
+	files, err := compiler.Compile(ctx, paths...)
+	if err != nil {
+		return nil, err
+	}
+	fileDescriptorProtos := make([]*descriptorpb.FileDescriptorProto, len(files))
+	for i, file := range files {
+		fileDescriptorProtos[i] = protoutil.ProtoFromFileDescriptor(file)
+	}
+	return fileDescriptorProtos, nil
+}

response_writer.go

@@ -198,7 +198,7 @@ func (r *ResponseWriter) toCodeGeneratorResponse() (*pluginpb.CodeGeneratorRespo
 	r.lock.RLock()
 	defer r.lock.RUnlock()
 
-	if r.responseSupportedFeatures&uint64(pluginpb.CodeGeneratorResponse_FEATURE_SUPPORTS_EDITIONS) == 0 {
+	if r.responseSupportedFeatures&uint64(pluginpb.CodeGeneratorResponse_FEATURE_SUPPORTS_EDITIONS) != 0 {
 		if r.responseMinimumEdition == 0 {
 			r.addSystemError(
 				errors.New("CodeGeneratorResponse: FEATURE_SUPPORTS_EDITIONS specified but no minimum_edition set"),

validate.go

@@ -45,13 +45,15 @@ func validateCodeGeneratorRequest(request *pluginpb.CodeGeneratorRequest) error
 	); err != nil {
 		return err
 	}
-	if err := validateCodeGeneratorRequestFileDescriptorProtos(
-		"source_file_descriptors",
-		request.GetSourceFileDescriptors(),
-		request.GetFileToGenerate(),
-		true,
-	); err != nil {
-		return err
+	if len(request.GetSourceFileDescriptors()) > 0 {
+		if err := validateCodeGeneratorRequestFileDescriptorProtos(
+			"source_file_descriptors",
+			request.GetSourceFileDescriptors(),
+			request.GetFileToGenerate(),
+			true,
+		); err != nil {
+			return err
+		}
 	}
 	if version := request.GetCompilerVersion(); version != nil {
 		if major := version.GetMajor(); major < 0 {