File property is being left out of the resulting rawSourceMap

[mareksuscak]

Hey, not sure if this is an issue of the multi-stage-sourcemap package but so far I have traced it, it looks like the issue of this package so here's the thing:

I'm using gulp-stylus v2.0.0 with autoprefixer-stylus 0.5.0 and trying to generate inline source maps using gulp-sourcemaps v1.3.0 on Windows 7 x64, node.js v0.10.36 as follows:

gulp.src('./src/styles/main.styl')
  .pipe(plugins.sourcemaps.init())
  .pipe(plugins.stylus({
    compress: production,
    use: [
      autoprefixer({ browsers: ['last 2 versions'] })
    ]
  }))
  .pipe(plugins.sourcemaps.write())
  .pipe(gulp.dest('./dist/styles/'))

But I'm getting the following error message:

Potentially unhandled rejection [2] Error: Source map to be applied is missing the "file" property
    at assertProperty (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\vinyl-sourcemaps-apply\inde
x.js:32:13)
    at applySourceMap (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\vinyl-sourcemaps-apply\inde
x.js:11:3)
    at D:\Development\youcon-softphone\node_modules\gulp-stylus\index.js:39:13
    at tryCatchReject (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\accord\node_modules\when\li
b\makePromise.js:845:30)
    at runContinuation1 (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\accord\node_modules\when\
lib\makePromise.js:804:4)
    at Fulfilled.when (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\accord\node_modules\when\li
b\makePromise.js:592:4)
    at Pending.run (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\accord\node_modules\when\lib\m
akePromise.js:483:13)
    at Scheduler._drain (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\accord\node_modules\when\
lib\Scheduler.js:62:19)
    at Scheduler.drain (D:\Development\youcon-softphone\node_modules\gulp-stylus\node_modules\accord\node_modules\when\l
ib\Scheduler.js:27:9)
    at process._tickCallback (node.js:442:13)

From what I understand autoprefixer-stylus uses multi-stage-sourcemap and multi-stage-sourcemap causes rawSourceMap to lose "file" property because it's not passed to a Generator object and it seems that the Generator object of source-map package doesn't add this automatically. After reading the readme file of this project it seems that this is an unexpected behaviour because in the example there's a file property.

File property is required by vinyl-sourcemaps-apply package which is a dependency of the gulp-stylus package.