Gulp watch doesn't not compile my .scss at each modification - gulp

Question

I encounter a problem with Gulp, I can not compile my .scss at each modification. When I run "gulp watch" and make changes in my css, nothing happens.
gulp css works, gulp watch doesn't work.
Yet everything looks good.
Do you have an idea ?
Thanks !
// Requires
var gulp = require('gulp');
// Include plugins
var sass = require('gulp-sass');
var concat = require('gulp-concat');
var rename = require('gulp-rename');
var minifycss = require('gulp-minify-css');
// var sourcemaps = require('gulp-sourcemaps');
var autoprefixer = require('gulp-autoprefixer');
// tâche CSS = compile vers knacss.css et knacss-unminified.css
gulp.task('css', function () {
return gulp.src('./src/assets/css/style.scss')
.pipe(sass())
.pipe(autoprefixer())
.pipe(rename('knacss.css'))
.pipe(gulp.dest('./dist/assets/css/'))
.pipe(rename('style.css'))
//.pipe(sourcemaps.init())
.pipe(minifycss())
//.pipe(sourcemaps.write('.', {includeContent: false}))
.pipe(gulp.dest('./dist/assets/css/'));
});
// Watcher
gulp.task('watch', function() {
gulp.watch(['./src/assets/css/*.scss'], ['css']);
});
gulp.task('default', ['css']);

Answer 1

Gulp watch doesn't not compile my .scss at each modification
That's because you don't tell it to.
You are only watching *.scss files in ./src/assets/css, not in subfolders.
To include subfolders, use this syntax:
gulp.task('watch', function() {
gulp.watch(['./src/assets/css/**/*.scss'], ['css']);
});

Answer 2

try with something like.
//SASS task
gulp.task('sass', function () {
var sassPath = {
cssSrc: ['./src/assets/css/*.scss'], cssDest: './src/assets/css/'
};
gulp.src(sassPath.cssSrc)
.pipe(sass().on('error', sass.logError))
.pipe(gulp.dest(sassPath.cssDest))
.pipe(livereload());
});
and then in your watch:
// Watcher
gulp.task('watch', function() {
gulp.watch(['./src/assets/css/*.scss'], ['sass']);
});
and:
gulp.task('default', ['sass','css']);