gulp: target.pipe transform is never called

I edit my "index" task with custom transform function

however when i run gulp serve i see only hello world1

why is hello world2 isn't print.

gulp.task('index', function() {
    var target = gulp.src('./public/index.html');
    var sources = gulp.src(config.appjs.concat(config.appcss), { read: false });

    gutil.log('Hello world1!');


    return target.pipe(inject(sources), {
            starttag: '// inject:js',
            endtag: '// endinject',
            transform: function(filepath, file, i, length) {

                gutil.log('Hello world2!');

                var n = str.indexOf("/");
                if (n > -1)  return  filepath.substr(n,
                    filepath.length());
                return  filepath;
            }
        })
        .pipe(wiredep({}))
        .pipe(gulp.dest('./dev'))
        .pipe(browserSync.stream());
});