highland-process/lib/process.js

Utility that lets you turn a process into a highland stream.

var _ = require('highland'),
    errorsTo = require('highland-errors-to');

exports.from = function from(process) {
  return _.merge([
    _(process.stdout),
    _(process.stderr).consume(errorConsumer())
  ]);
};

exports.through = function through(process) {
  return function(stream) {
    var errors,
        errorsToResults,
        out = exports.from(process);

    errorsToResults = errorsTo(stream);
    stream = errorsToResults.stream;
    errors = errorsToResults.errors;

    stream.pipe(process.stdin);

    return _.merge([
      out,
      errors
    ]);
  };
};

// TODO(ibash) remove this in favor of using the actual StreamError from highland
// ref: https://github.com/Datahero/datahero-node/issues/9676
function StreamError(err) {
  this.__HighlandStreamError__ = true;
  this.error = err;
}

function errorConsumer() {
  var message = '';

  return function consumer(error, value, push, next) {
    var errorMessages;

    if (error) {
      push(error);
      return next();
    }

    if (value !== _.nil) {
      message += value;
    }

    if (message.indexOf('\n') !== -1) {
      errorMessages = message.split('\n');
      // don't create an error for the last message, since it might not be complete yet
      for (var i = 0; i < errorMessages.length - 1; i++) {
        push(new Error(errorMessages[i]));
      }

      message = errorMessages[errorMessages.length - 1];
    }

    if (value === _.nil) {
      if (message) {
        push(new Error(message));
      }
      return push(null, _.nil);
    }

    next();
  };
}