Why is gulp watch collecting files endlessly?

Question

gulp.js

Hello, I ran into a problem: When you change the file 1.styl - watch starts to run endlessly. Compiled a basic example, but it refuses to work. gulp version - 4.0

const gulp   = require('gulp')
const stylus = require('gulp-stylus')

gulp.task('watch', function(){
    gulp.watch('./src/**/*.styl', gulp.parallel('build'));
});

gulp.task('build', function(){
  return gulp.src('./src/styl/1.styl')
  .pipe(stylus())
  .pipe(gulp.dest('./build'))
})

gulp.task('default', gulp.parallel('build', 'watch'))

Experimentally I was able to determine that if we replace

gulp.task('build', function(){
  return gulp.src('./src/styl/1.styl')
  .pipe(stylus())
  .pipe(gulp.dest('./build'))
})

on the

gulp.task('build', function(done){
  console.log('build');
  done();
})

that works. But

gulp.task('build', function(done){
  console.log(gulp.src('src/styl/1.styl'));
  done();
})

endless execution starts again

Answer 1

gulp.parallel('build', 'watch') this thing loops everything for you, but in fact the build and watch tasks do the same thing tobish build collects tsfesr looks at the changes and again collects as a result in a circle to infinity