Gulp TypeError: glob pattern string required. What is the problem?

Question

gulp.js

All tasks work fine, there is a problem when starting watch. As soon as I save the modified file, an error occurs:

TypeError: glob pattern string required
    at new Minimatch (/var/www/facts/node_modules/gulp-watch/node_modules/glob/node_modules/minimatch/minimatch.js:108:11)
    at setopts (/var/www/facts/node_modules/gulp-watch/node_modules/glob/common.js:112:20)
    at new Glob (/var/www/facts/node_modules/gulp-watch/node_modules/glob/glob.js:117:3)
    at EventEmitter.processEvent (/var/www/facts/node_modules/gulp-watch/index.js:92:35)
    at EventEmitter.emit (events.js:106:17)
    at EventEmitter.<anonymous> (/var/www/facts/node_modules/gulp-watch/node_modules/chokidar/index.js:152:38)
    at EventEmitter.FSWatcher._emit (/var/www/facts/node_modules/gulp-watch/node_modules/chokidar/index.js:179:5)
    at EventEmitter.<anonymous> (/var/www/facts/node_modules/gulp-watch/node_modules/chokidar/lib/nodefs-handler.js:263:16)
    at Object.oncomplete (fs.js:107:15)

Content of gulpfile.js

var gulp = require('gulp');
var less = require('gulp-less');
var path = require('path');
var watch = require('gulp-watch');
var concat = require('gulp-concat');

var bemdir = 'gulp/less/bem/';
var concat_less = 'gulp/less/concat-less/';
var main_less = 'gulp/less/main.less';
var css_destdir = 'css';
  
gulp.task('concat-1280', function() {
  
  return gulp.src(bemdir + '**/*.1280.less')
    .pipe(concat('bem.1280.less'))
    .pipe(gulp.dest(concat_less));
});	


gulp.task('concat-800', function() {
  
  return gulp.src(bemdir + '**/*.800.less')
    .pipe(concat('bem.800.less'))
    .pipe(gulp.dest(concat_less));
});


gulp.task('concat-480', function() {

  return gulp.src(bemdir + '**/*.480.less')
    .pipe(concat('bem.480.less'))
    .pipe(gulp.dest(concat_less));
});

gulp.task('less', function () {
  gulp.src(main_less)
  .pipe(less())
  .pipe(gulp.dest(css_destdir));
});
  
gulp.task('watch', function() {
  watch(bemdir, ['concat-1280', 'concat-800', 'concat-480']);
  watch(concat_less, ['less']);
});

Version of gulp 4.0, on 3.9 the same error.

Answer 1

The problem with this particular error is that the paths must be specified not to directories, but to files.