Task dependencies in Gulp - gulp

Question

There is the following gulpfile.js
const { watch, src, dest, parallel, series } = require('gulp')
const uglify = require('gulp-uglify')
const browserSync = require('browser-sync').create()
const htmlMin = require('gulp-htmlmin')
const cleanCSS = require('gulp-clean-css')
const imagemin = require('gulp-imagemin')
const hash = require('gulp-hash') // !!!
const references = require('gulp-hash-references') // !!!
const del = require('del')
const path = require('path')
const manifestFile = 'asset-manifest.json'
const buildDir = './build'
function serve() {
browserSync.init({
server: {
baseDir: "./"
}
})
watch("./*.html").on('change', browserSync.reload)
watch("./css/**/*.css").on('change', browserSync.reload)
watch("./**/*.js").on('change', browserSync.reload)
}
function buildHTML(cb) {
src('index.html')
.pipe(references(manifestFile)) // replace file paths in index.html according to the manifest
.pipe(htmlMin({
collapseWhitespace: true
}))
.pipe(dest(buildDir))
cb()
}
function buildCSS(cb) {
src('./css/**/*.css')
.pipe(cleanCSS())
.pipe(hash())
.pipe(dest(path.join(buildDir, 'css')))
.pipe(hash.manifest(manifestFile)) // generate a manifest file
.pipe(dest('.'))
cb()
}
function buildJS(cb) {
src(['./**/*.js', '!./node_modules/**', '!./gulpfile.js'])
.pipe(uglify())
.pipe(hash())
.pipe(dest('build/'))
.pipe(hash.manifest(manifestFile)) // generate a manifest file
.pipe(dest('.'))
cb()
}
function buildImages(cb) {
src('./img/**/*.png')
.pipe(imagemin([
imagemin.optipng({ optimizationLevel: 7 })
]))
.pipe(dest(path.join(buildDir, 'img')))
cb()
}
exports.build = series(buildJS, buildCSS, buildHTML) // !!!
exports.default = serve
I'm trying to hash *.css and *.js file names and replace their old names with hashed ones in the build/index.html file. But the problem is that the function "buildHTML" starts working earlier than the "asset-manifest.json" file created. What am I doing wrong?

Answer 1

You have to return the streams created by your functions to ensure that they run in the expected order and to catch any possible errors. No need to use a callback:
function buildHTML() {
return src('index.html')
.pipe(references(manifestFile)) // replace file paths in index.html according to the manifest
.pipe(htmlMin({
collapseWhitespace: true
}))
.pipe(dest(buildDir));
}
function buildCSS() {
return src('./css/**/*.css')
.pipe(cleanCSS())
.pipe(hash())
.pipe(dest(path.join(buildDir, 'css')))
.pipe(hash.manifest(manifestFile)) // generate a manifest file
.pipe(dest('.'));
}
function buildJS() {
return src(['./**/*.js', '!./node_modules/**', '!./gulpfile.js'])
.pipe(uglify())
.pipe(hash())
.pipe(dest('build/'))
.pipe(hash.manifest(manifestFile)) // generate a manifest file
.pipe(dest('.'));
}
function buildImages() {
return src('./img/**/*.png')
.pipe(imagemin([
imagemin.optipng({ optimizationLevel: 7 })
]))
.pipe(dest(path.join(buildDir, 'img')));
}