support protobuf library version 4

The getSyntax method on messageDescriptor.getFile() got removed
in protobuf version 4.
This change gets the syntax information directly from the proto, this
works in protobuf v3 and v4.


fixes apache#3175

see also apache#3182

Author: uwemaurer

parquet-protobuf/src/main/java/org/apache/parquet/proto/ProtoWriteSupport.java

@@ -445,10 +445,14 @@ final void writeField(Object value) {
 
     private void writeAllFields(MessageOrBuilder pb) {
       Descriptor messageDescriptor = pb.getDescriptorForType();
-      Descriptors.FileDescriptor.Syntax syntax =
-          messageDescriptor.getFile().getSyntax();
+      String syntax =
+          messageDescriptor.getFile().toProto().getSyntax();
+      if ("editions".equals(syntax)) {
+          throw new UnsupportedOperationException("protocol buffers 'editions' not supported");
+      }
+      boolean isProto2 = !"proto3".equals(syntax);
 
-      if (Descriptors.FileDescriptor.Syntax.PROTO2.equals(syntax)) {
+      if (isProto2) {
         // Returns changed fields with values. Map is ordered by id.
         Map<FieldDescriptor, Object> changedPbFields = pb.getAllFields();
 
@@ -464,7 +468,7 @@ private void writeAllFields(MessageOrBuilder pb) {
           int fieldIndex = fieldDescriptor.getIndex();
           fieldWriters[fieldIndex].writeField(entry.getValue());
         }
-      } else if (Descriptors.FileDescriptor.Syntax.PROTO3.equals(syntax)) {
+      } else {
         List<FieldDescriptor> fieldDescriptors = messageDescriptor.getFields();
         for (FieldDescriptor fieldDescriptor : fieldDescriptors) {
           FieldDescriptor.Type type = fieldDescriptor.getType();