#911 Enhance command sysl pb --mode=pb to output binary message

cmd/sysl/cmd_protobuf.go

@@ -20,9 +20,9 @@ func (p *protobuf) Name() string       { return "protobuf" }
 func (p *protobuf) MaxSyslModule() int { return 1 }
 
 func (p *protobuf) Configure(app *kingpin.Application) *kingpin.CmdClause {
-	cmd := app.Command(p.Name(), "Generate textpb/json").Alias("pb")
+	cmd := app.Command(p.Name(), "Generate textpb/json/binary").Alias("pb")
 	cmd.Flag("output", "output file name").Short('o').Default("-").StringVar(&p.output)
-	opts := []string{"textpb", "json"}
+	opts := []string{"textpb", "json", "pb"}
 	cmd.Flag("mode", fmt.Sprintf("output mode: [%s]", strings.Join(opts, ","))).
 		Default(opts[0]).
 		EnumVar(&p.mode, opts...)
@@ -44,8 +44,17 @@ func (p *protobuf) Execute(args cmdutils.ExecuteArgs) error {
 		}
 		return pbutil.JSONPB(args.Modules[0], p.output, args.Filesystem)
 	}
+
+	if p.mode == "" || p.mode == "textpb" {
+		if p.output == "-" {
+			return pbutil.FTextPB(os.Stdout, args.Modules[0])
+		}
+		return pbutil.TextPB(args.Modules[0], p.output, args.Filesystem)
+	}
+
+	// output format is binary
 	if p.output == "-" {
-		return pbutil.FTextPB(os.Stdout, args.Modules[0])
+		return pbutil.GeneratePBBinaryMessage(os.Stdout, args.Modules[0])
 	}
-	return pbutil.TextPB(args.Modules[0], p.output, args.Filesystem)
+	return pbutil.GeneratePBBinaryMessageFile(args.Modules[0], p.output, args.Filesystem)
 }

pkg/pbutil/output.go

@@ -7,6 +7,7 @@ import (
 	"github.com/spf13/afero"
 	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/encoding/prototext"
+	"google.golang.org/protobuf/proto"
 	"google.golang.org/protobuf/reflect/protoreflect"
 )
 
@@ -64,3 +65,30 @@ func FTextPB(w io.Writer, m protoreflect.ProtoMessage) error {
 	_, err = w.Write(mt)
 	return err
 }
+
+// GeneratePBBinaryMessageFile generates binary message to the file specified by `filename`.
+func GeneratePBBinaryMessageFile(m protoreflect.ProtoMessage, filename string, fs afero.Fs) error {
+	if m == nil {
+		return fmt.Errorf("module is nil: %#v", filename)
+	}
+
+	f, err := fs.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return GeneratePBBinaryMessage(f, m)
+}
+
+// GeneratePBBinaryMessage generates binary message to IO writer specified by `w`.
+func GeneratePBBinaryMessage(w io.Writer, m protoreflect.ProtoMessage) error {
+	if m == nil {
+		return fmt.Errorf("module is nil")
+	}
+	bytes, err := proto.Marshal(m)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(bytes)
+	return err
+}

pkg/pbutil/output_test.go

@@ -121,3 +121,43 @@ func TestFTextPBNilModule(t *testing.T) {
 	require.Error(t, FTextPB(&output, nil))
 	assert.Equal(t, "", output.String())
 }
+
+func TestGeneratePBBinaryMessage(t *testing.T) {
+	t.Parallel()
+
+	unmarshalled := &sysl.Module{}
+	var output bytes.Buffer
+	require.NoError(t, GeneratePBBinaryMessage(&output, testModule()))
+	require.NoError(t, proto.Unmarshal(output.Bytes(), unmarshalled))
+	assert.True(t, proto.Equal(unmarshalled, protoreflect.ProtoMessage(testModule())))
+}
+
+func TestGeneratePBBinaryMessageNilModule(t *testing.T) {
+	t.Parallel()
+
+	var output bytes.Buffer
+	require.Error(t, GeneratePBBinaryMessage(&output, nil))
+	assert.Equal(t, "", output.String())
+}
+
+func TestGeneratePBBinaryMessageFile(t *testing.T) {
+	t.Parallel()
+
+	unmarshalled := &sysl.Module{}
+	fs := afero.NewMemMapFs()
+	filename := "/out.pb"
+	require.NoError(t, GeneratePBBinaryMessageFile(testModule(), filename, fs))
+	output, err := afero.ReadFile(fs, filename)
+	require.NoError(t, err)
+	require.NoError(t, proto.Unmarshal(output, unmarshalled))
+	assert.True(t, proto.Equal(unmarshalled, protoreflect.ProtoMessage(testModule())))
+}
+
+func TestGeneratePBBinaryMessageFileNilModule(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewMemMapFs()
+	filename := "/out.pb"
+	require.Error(t, GeneratePBBinaryMessageFile(nil, filename, fs))
+	syslutil.AssertFsHasExactly(t, fs)
+}