add kCanonicalJson to fileutil

Author: lperron

ortools/util/file_util.cc

@@ -68,7 +68,7 @@ bool ReadFileToProto(absl::string_view filename,
   if (proto->ParseFromString(data)) {
     // NOTE(user): When using ParseFromString() from a generic
     // google::protobuf::Message, like we do here, all fields are stored, even
-    // if their are unknown in the underlying proto type. Unless we explicitly
+    // if they are unknown in the underlying proto type. Unless we explicitly
     // discard those 'unknown fields' here, our call to ByteSizeLong() will
     // still count the unknown payload.
     proto->DiscardUnknownFields();
@@ -124,7 +124,7 @@ bool WriteProtoToFile(absl::string_view filename,
         return false;
       }
       break;
-    case ProtoWriteFormat::kJson:
+    case ProtoWriteFormat::kJson: {
       google::protobuf::util::JsonPrintOptions options;
       options.add_whitespace = true;
       options.always_print_primitive_fields = true;
@@ -137,6 +137,18 @@ bool WriteProtoToFile(absl::string_view filename,
       }
       file_type_suffix = ".json";
       break;
+    }
+    case ProtoWriteFormat::kCanonicalJson:
+      google::protobuf::util::JsonPrintOptions options;
+      options.add_whitespace = true;
+      if (!google::protobuf::util::MessageToJsonString(proto, &output_string,
+                                                       options)
+               .ok()) {
+        LOG(WARNING) << "Printing to stream failed.";
+        return false;
+      }
+      file_type_suffix = ".json";
+      break;
   }
   if (gzipped) {
     std::string gzip_string;

ortools/util/file_util.h

@@ -44,13 +44,16 @@ Proto ReadFileToProtoOrDie(absl::string_view filename) {
   return proto;
 }
 
-enum class ProtoWriteFormat { kProtoText, kProtoBinary, kJson };
+// Specifies how the proto should be formatted when writing it to a file.
+// kCanonicalJson applies Proto3 to JSON encoding conventions and converts field
+// names to lower camel-case.
+enum class ProtoWriteFormat { kProtoText, kProtoBinary, kJson, kCanonicalJson };
 
 // Writes a proto to a file. Supports the following formats: binary, text, JSON,
 // all of those optionally gzipped. Returns false on failure.
 // If 'proto_write_format' is kProtoBinary, ".bin" is appended to file_name. If
-// 'proto_write_format' is kJson, ".json" is appended to file_name. If 'gzipped'
-// is true, ".gz" is appended to file_name.
+// 'proto_write_format' is kJson or kCanonicalJson, ".json" is appended to
+// file_name. If 'gzipped' is true, ".gz" is appended to file_name.
 bool WriteProtoToFile(absl::string_view filename,
                       const google::protobuf::Message& proto,
                       ProtoWriteFormat proto_write_format, bool gzipped = false,