How to parse a valid JSON file that has non valid field inside?

Question

I know that this may seem a strange question, but, the input of my algorithm is a stream of JSON strings composed by syntactically correct JSON blocks, at least for all blocks but this. A block in the stream has this structure:

{
  "comment",
  {
    "author":"X",
    "body":"Hello world",
    "json_metadata":"{"tags":["hello, world"],"community":"programming","app":"application_for_publish"}",
    "parent_author":"waggy6",
    "parent_permlink":"programming_in_c",
    "permlink":"re-author-programming_in_c-20180916t035418244z",
    "title":"some_title"
  }
}

So, everything works fine, up to arriving to this block, that I don't know how to parse. The field that gives me troubles is the "json_metadata" one:

{
  "comment", 
  {
    "author": "Y",
    "body": "Hello another world!",
    "json_metadata": ""{\"tags\":[\"hello\",\"world\"],\"app\":\"application_for_publish_content\",\"format\":\"markdown+html\",\"pollid\":\"p_id\",\"image\":[\"https://un.useful.url/path/image.png\"]}"",
    "parent_author": "",
    "parent_permlink": "helloworld",
    "permlink": "hello_world_programming_in_c-2017319t94958596z",
    "title": "Hello World in C!"
  }
}

It's like this field has been parsed twice, when the data has been acquired. I'm using rapidjson as parsing tool, in C++. The piece of code related to this problem is the following:

static std::string parseNode(const Value &node){
   string toret = "";
   if (node.IsBool())          toret = toret + to_string(node.GetBool());
   else if (node.IsInt())      toret = toret + to_string(node.GetInt());
   else if (node.IsUint())     toret = toret + to_string(node.GetUint());
   else if (node.IsInt64())    toret = toret + to_string(node.GetInt64());
   else if (node.IsUint64())   toret = toret + to_string(node.GetUint64());
   else if (node.IsDouble())   toret = toret + to_string(node.GetDouble());
   else if (node.IsString())   toret = toret + node.GetString();
   else if (node.IsArray())    toret = toret + parseArray(node); // parse the given array
   else if (node.IsObject())   toret = toret + parseObject(node); // parse the given object
   return toret;
}

...

std::string search_member(Value& js, std::string member){
   Value::ConstMemberIterator itr = js.FindMember(member.c_str());
   std::string els = "";
   if(itr != js.MemberEnd())
      els = parseNode(itr->value) + " ";
   return els;
}

...

// op_struct type is Value*; it is the Value* that refers to all the fields of the block
std::string json_m = (*op_struct)["json_metadata"];
std::string elements = "";
if((json_m.compare("") != 0) && (json_m.compare("{}") != 0) && (json_m.compare("""") != 0)){
   Document js;
   js.Parse<0>(json_m.c_str());
   elements = elements + search_member(js, "community") + search_member(js, "tags") + search_member(js, "app");
}
Comment * comment = new Comment(title + " " + body + " " + elements, auth);

...

The problem occurs in the js.FindMember(member.c_str()); row, in the search_member() function, because js.Parse<0>(json_m.c_str()); recognizes that the input is a valid JSON, and indeed it is valid, it refers to:

""{\"tags\":[\"hello\",\"world\"],\"app\":\"application_for_publish_content\",\"format\":\"markdown+html\",\"pollid\":\"p_id\",\"image\":[\"https://un.useful.url/path/image.png\"]}""

But, then, the result of this computation, is the string:

"{"tags":["hello","world"],"app":"application_for_publish_content","format":"markdown+html","pollid":"p_id","image"

And for this reason, the FindMember() function can not find any tags, community or app field, since it is recognized as a string.

My question is: is there any way (different by just skipping this block) with which I can recognize such special cases?

How to parse a valid JSON file that has non valid field inside?

0 Answers