using Less Autoprefix plugin breaks sourcemaps (sources property)

[bassjobsen]

When i using the following gulpfile.js:

var gulp = require('gulp'),
    less = require('gulp-less'),
    sourcemaps = require('gulp-sourcemaps');

var LessPluginAutoPrefix = require('less-plugin-autoprefix'),
    autoprefix= new LessPluginAutoPrefix({browsers: ["last 2 versions"]});

gulp.task('default', function () {
  return gulp
 .src('./less/**/*.less')
 .pipe(sourcemaps.init())
  .pipe(less({
    plugins: [autoprefixer]
   }))
  .pipe(sourcemaps.write('./'))
  .pipe(gulp.dest('./css'));
});

The source map got a invalid second value for the sources property ("../<input css 1>").

The sourcemap code looks like that shown below:

{"version":3,"sources":["t.less","../<input css 1>"],"names":[],"mappings":

When using autoprefixer = require('gulp-autoprefixer'); with .pipe(autoprefixer()) instead of the plugin, the generated sourcemap is correct.

To verify if the problem is not related to the Less Autoprefix plugin itself, i have compiled the Less code with the command line Less compiler and the autoprefix plugin by running: lessc less/t.less css/t.css --autoprefix --source-map --source-map-less-inline. Also the preceding command gives an sourcemap as expected ({"version":3,"sources":["../less/t.less","t.css"],"names":[])

[yocontra]

No idea - less should be dealing with the sourcemaps of plugins before it even hands data back to us. Will take some debugging.

[bassjobsen]

I understand now your are using inline sourcemap. So i tested lessc less/t.less --autoprefix --source-map --source-map-less-inline --source-map-map-inline which generates a wrong sourcemap. So the issue is related to the Less plugin (or Less) indeed.

[yocontra]

Reopen on the relevant repo and link to this issue so people can track the progress