usemin + sourcemaps generates maps with empty names and mappings

[joanscript]

I am facing some problems generating sourcemaps using usemin. I am using the latest versions of the plugins. Here there is my task, which is very simple:

var gulp = require('gulp');  //"3.5.6"
var usemin = require('gulp-usemin'); //"0.3.8"
var uglify = require('gulp-uglify'); //"0.2.1"
var rev = require('gulp-rev'); //"0.2.1"
var sourcemaps = require('gulp-sourcemaps'); //"1.2.8"

gulp.task('default', function() {
  gulp.src('*.php')
    .pipe(usemin({
      js: [sourcemaps.init(), uglify(), rev(), sourcemaps.write('.')]
    }))
    .pipe(gulp.dest('dist/'));
});

And here there is the output, a map without the mappings and names. userfile-652284cb.js.map

{"version":3,"file":"js/userfile-652284cb.js","names":[],"mappings":"","sources":["js/userfile.js"]}

What am I doing wrong?

[zont]

Try:

gulp.task('default', function() {
  gulp.src('*.php')
    .pipe(usemin({
      js: [sourcemaps.init(), 'concat', uglify(), rev(), sourcemaps.write('.')]
    }))
    .pipe(gulp.dest('dist/'));
});

[jskrepnek]

I got hung up on this for a long time too. Eventually it hit me and I finally noticed this small tidbit in the docs:

If exist used for modify files. If does not contain string 'concat', then it added as first member of pipeline

The apparent issue that @joanscript and I were struggling with is a misunderstanding of the default behaviour of usemin, which is to concat the source files before running the pipeline plugins (i.e.: generating sourcemaps). The result is a sourcemap of the resulting concatenated file - not as useful :).

@zont While I think this can be closed, better highlighting of the default behaviour would help steer people away from this sinkhole. Would you take a pull on the readme?