JSON: Add function AddIndent()

[AbdealiLoKo]

I've had instances where I would like to first generate a JSON object in one function and then embed this into a array in another JSON object.

In such cases, I do something like:

    dmlc::JSONWriter writer(&os);
    writer.BeginArray();
    for (size_t i = 0; i < dump.size(); ++i) {
      if (i != 0) writer.WriteArraySeperator();
      os << dump[i];  // Dump the previously generated JSON here
    }
    writer.EndArray();

But this means the indenting is not right anymore. Would be nice to be able to fix the indenting with:

    dmlc::JSONWriter writer(&os);
    writer.BeginArray();
    for (size_t i = 0; i < dump.size(); ++i) {
      if (i != 0) writer.WriteArraySeperator();
      os << dmlc::JSONWriter.AddIndent(dump[i], 1);  // Dump the previously generated JSON here
    }
    writer.EndArray();

or something similar

[albanjiang]

👍

[szha]

IMO the JSONWriter shouldn't handle indentation in default setting. The size would be smaller.