Import CSS from node_modules using Gulp-SASS

What works for me, in 2020, is this:

function styles() {
    return (
      gulp.src(paths.styles.src)
        .pipe(sourcemaps.init())
        .pipe(sass({
                    includePaths: ['./node_modules/purecss-sass/vendor/assets/stylesheets/',
                                  './node_modules/modularscale-sass/stylesheets/',
                                  './node_modules/typi/scss/'
                                  ]
                  }))
        .on("error", sass.logError)
        .pipe(postcss([autoprefixer(), cssnano()]))
        .pipe(sourcemaps.write())
        .pipe(gulp.dest(paths.styles.dest))
        .pipe(browserSync.stream())
    );
}

Now in the scss files, I can

@import 'modularscale';
@import 'typi';
@import 'purecss';

The other options seem to be:

1. put the full paths to the main _somelibrary.scss file directly in the scss files (minus the extension), so something like:

@import '../../node_modules/purecss-sass/vendor/assets/stylesheets/_purecss';

2. Put includePaths: ['./node_modules'] and add the relative paths in the scss files:

@import 'purecss-sass/vendor/assets/stylesheets/_purecss';

SASS compiler doesn't know where to look for the files. The location needs to be specified.

gulp.task('sass', function () {
  return gulp.src(['source/assets/css/**.scss', '!source/assets/css/**/_*.[scss|sass'])
    .pipe(sass({
      includePaths: ['node_modules']
    }))
    .pipe(gulp.dest('output/assets/css'));
});