Node.js stream.Transform bug / oddity.

transformerrs.js

var util = require('util');
var stream = require('stream');
var fs = require('fs');

// # 1. With objectMode: true

var ObjectParser = function(opts) {
  stream.Transform.call(this, {
    decodeStrings: true, // Writable option, ensure _transform always gets a Buffer
    objectMode: true // Readable option, .read(n) should return a single value, rather than a Buffer
  });
};
util.inherits(ObjectParser, stream.Transform);

ObjectParser.prototype._transform = function(chunk, encoding, done) {
  console.log('chunk=', chunk, 'encoding=', encoding);
  done();
};

var obj_parser2 = new ObjectParser();
fs.createReadStream('transformerrs.js').pipe(obj_parser2);

// output -> chunk= <Buffer 76 61 72 20 75 74 69 6c 20 3d 20 ...> encoding= buffer (GREAT!)

var obj_parser1 = new ObjectParser();
obj_parser1.write('Here make me an object.');

// output -> chunk= Here make me an object. encoding= utf8 (WTF?)


// # 2. No objectMode. In this case, decodeStrings needn't be specified

var NormalParser = function(opts) {
  stream.Transform.call(this, {
    decodeStrings: true // Writable option, ensure _transform always gets a Buffer
  });
};
util.inherits(NormalParser, stream.Transform);

NormalParser.prototype._transform = function(chunk, encoding, done) {
  console.log('chunk=', chunk, 'encoding=', encoding);
  done();
};

var norm_parser2 = new NormalParser();
fs.createReadStream('transformerrs.js').pipe(norm_parser2);

// output -> chunk= <Buffer 76 61 72 20 75 74 69 6c 20 3d 20 72  ...> encoding= buffer (GREAT!)

var norm_parser1 = new NormalParser();
norm_parser1.write('These are just words.');

// output -> chunk= <Buffer 54 68 65 73 65 20 61 72 65 20 6a 75 73 74 20 77 6f 72 64 73 2e> encoding= utf8 (SWEET!)