stream: Writing null to objectMode Transform is unrecoverable #5711
Description
If null is written to an instance of stream.Transform, the stream does not complete additional writes, emit additional data, nor emit an 'error' or 'end' event. As an example, consider the following:
var stream = require('stream');
var s = new stream.Transform({
objectMode: true,
transform: function(chunk, encoding, callback) {
console.log('transform', chunk);
callback(null, chunk);
}
});
s.on('data', console.log.bind(console, 'data'));
s.on('error', console.log.bind(console, 'error'));
s.on('end', console.log.bind(console, 'end'));
s.write('input1', console.log.bind(console, 'finished write1'));
s.write(null, console.log.bind(console, 'finished write2'));
s.write('input2', console.log.bind(console, 'finished write3'));
s.end();This prints
transform input1
data input1
finished write1
Instead of write2 either causing an error or being ignored and write3 completing normally followed by 'end'.
This occurs because null writechunk skips ._transform without calling ts.writecb causing Writable to buffer subsequent writes waiting for ._write(null, ...) to complete. This behavior has been present since 26ca7d7.
If there is agreement on the appropriate behavior, I can work up a PR. I would suggest removing the ts.writechunk !== null check so that the value will be passed to ._transform to match the current handling of undefined. If _.transform returns it unchanged, it would be ignored, like undefined. Discarding the write, with or without error, could be reasonable as well.
Thanks for considering,
Kevin