gulp task throwing error on second time run - gulp

Question

I have two folders both of which contain some html template files. I need to minify these files to separate folders.
folder structure
|src
|--clientTemplates
|----abc.html
|----xyz.html
|--serverTemplates
|----abc.html
|----xyz.html
required destination folder
|dist
|--client
|----abc.html
|----xyz.html
|--server
|----abc.html
|----xyz.html
following is my gulpfile where I have my tasks defined for the
var gulp = require('gulp');
var htmlmin = require('gulp-htmlmin');
var replace = require('gulp-replace');
var del = require('del');
var minOptions = {
collapseWhitespace: true,
minifyJS: { output: { quote_style: 1 } },
minifyCSS: true
};
gulp.task('clean', function(done) {
del(['dist'], done());
});
gulp.task('minify:serverTemplates', function() {
return gulp
.src('src/serverTemplates/*.html')
.pipe(htmlmin(minOptions))
.pipe(replace('\\', '\\\\'))
.pipe(replace('"', '\\"'))
.pipe(gulp.dest('dist/server'));
});
gulp.task('minify:clientTemplates', function() {
return gulp
.src('src/clientTemplates/*.html')
.pipe(htmlmin(minOptions))
.pipe(gulp.dest('dist/client'));
});
gulp.task(
'default',
gulp.series('clean', 'minify:serverTemplates', 'minify:clientTemplates', function inSeries(done) {
done();
})
);
when I run the gulp command it works fine for the first time, but throws errors on alternate runs.
running gulp command first time
running gulp command second time
can't figure out what exactly is wrong there.
Also is there a way to run the two minification task parallel once the clean task has finished?
thanks for the help.

Answer 1

The callback you pass to del is wrong. Just return the promise:
gulp.task('clean', function() {
return del(['dist']);
});
As for running the minification tasks in parallel, use gulp.parallel:
gulp.task(
'default',
gulp.series(
'clean',
gulp.parallel('minify:serverTemplates', 'minify:clientTemplates')
)
);