reflect/protodesc: don't generate invalid syntax values

Fixes golang/protobuf#1575 When converting a protoreflect.FileDescriptor to a FileDescriptorProto, don't emit an invalid syntax. This can happen for placeholder files, which represent missing dependencies of a file. Change-Id: I1d2ae1bd9f89c8a92e751871ce5c02727505b5e2 Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/540455 Reviewed-by: Lasse Folger <[email protected]> Reviewed-by: Michael Stapelberg <[email protected]> LUCI-TryBot-Result: Go LUCI <[email protected]> Reviewed-by: Damien Neil <[email protected]>
protocolbuffers · Nov 8, 2023 · a8317fb · a8317fb
1 parent 9492118
commit a8317fb
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diff --git a/reflect/protodesc/file_test.go b/reflect/protodesc/file_test.go
@@ -15,6 +15,7 @@ import (
 	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/reflect/protoregistry"
 
+	"google.golang.org/protobuf/internal/filedesc"
 	"google.golang.org/protobuf/types/descriptorpb"
 )
 
@@ -1180,3 +1181,12 @@ func TestSourceLocations(t *testing.T) {
 		t.Errorf("visited %d descriptor, expected 30", numDescs)
 	}
 }
+
+func TestToFileDescriptorProtoPlaceHolder(t *testing.T) {
+	// Make sure placeholders produce valid protos.
+	fileDescriptor := ToFileDescriptorProto(filedesc.PlaceholderFile("foo/test.proto"))
+	_, err := NewFile(fileDescriptor, &protoregistry.Files{} /* empty files since placeholder has no deps */)
+	if err != nil {
+		t.Errorf("placeholder file descriptor proto is not valid: %s", err)
+	}
+}
diff --git a/reflect/protodesc/proto.go b/reflect/protodesc/proto.go
@@ -70,7 +70,7 @@ func ToFileDescriptorProto(file protoreflect.FileDescriptor) *descriptorpb.FileD
 	for i, exts := 0, file.Extensions(); i < exts.Len(); i++ {
 		p.Extension = append(p.Extension, ToFieldDescriptorProto(exts.Get(i)))
 	}
-	if syntax := file.Syntax(); syntax != protoreflect.Proto2 {
+	if syntax := file.Syntax(); syntax != protoreflect.Proto2 && syntax.IsValid() {
 		p.Syntax = proto.String(file.Syntax().String())
 	}
 	return p