gulp-sass discards changes from earlier in the pipeline when generating source maps

[jmm]

I believe there's a serious flaw in this plugin with the logic around file.sourceMap and opts.sourceComments. It results in node-sass attemping to re-read the file from disk, which discards changes from earlier in the gulp pipeline, and if an earlier change is a rename (e.g. with gulp-rename) it results in node-sass attemping to read a file which either doesn't exist or is the wrong file. Here are a couple of simple examples:

Given:

Gulp 3.8.10, gulp-sass 1.2.4, Ubuntu 12.

var
  gulp = require('gulp'),
  sourcemaps = require('gulp-sourcemaps'),
  rename = require('gulp-rename'),
  sass = require('gulp-sass'),
  through = require('through2');

This (rename):

gulp.task('default', function () {
  return gulp.src('./src/x.scss')
    .pipe(rename('y.scss'))
    .pipe(sourcemaps.init())
      .pipe(sass())
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('./dist'));
});

Results in:

stream.js:94
      throw er; // Unhandled stream error in pipe.
            ^
Error: Error: File to read not found or unreadable: src/y.scss

And here is an example with a simple plugin that changes file contents (prepends a comment):

var prefix = function () {
  var prefix = new Buffer("\n/* Added dynamically */\n", 'utf-8');

  return through.obj(function (file, enc, cb) {
    file.contents = Buffer.concat([prefix, file.contents]);
    this.push(file);
    cb();
  })
};

gulp.task('default', function () {
  return gulp.src('./src/x.scss')
    .pipe(prefix())
    .pipe(sourcemaps.init())
      .pipe(sass())
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('./dist'));
});

This results in the changes from the prefix plugin being discarded.

This means that the changes proposed in Consistent file handling #66 should not be accepted -- things need to go the other way.

If we're on the same page about this, I may work on a pull request.

[Snugug]

@dlmanning @Keats So I've tracked down this problem. We're passing the file name to node-sass for libsass to compile instead of passing along the data stream and we should probably be passing along the data stream. The problem, however, with passing along the data stream is that we then need to pass along all of the includePaths for that file which would require us (or node-sass, or libsass if we can convince either of them) to build a graph the includePaths.

@jmm, your rename problem can be resolved by renaming it after compiling your file. The prefix problem persists until we determine what we're going to do about the data issue

[jmm]

@Snugug

your rename problem can be resolved by renaming it after compiling your file

That example is just to illustrate one of the failure modes. But, doing the rename after isn't equivalent, because then the original name winds up in the sources array of the source map.

[Snugug]

@jmm Understood, see the rest of my comment about the underlying issue.

[jmm]

@Snugug Yup, I read it all, but even the rename case isn't fully solved until the underlying issue is corrected.

[Snugug]

Right, I'm looking into a solution now.

[jmm]

Great, thanks!

[Snugug]

@jmm Give this a test:

npm install snugug/gulp-sass#2.x-filedata --save-dev

I think I've fixed this to work as you're expecting. The two examples you've provided should now work.

[jmm]

Thanks @Snugug. I tried it and it does indeed work as it should now for the the test cases I posted.