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Revision files & more with gulp

Building a version of your app/site should be a matter of seconds and be completely automated, so you can do it often and find issues fast.

In the previous part of this series we started converting our php based website into a progressive web app (PWA) and added a gulpfile to convert our mustache templates to html. In this part we will revision our files with gulp and simplify our html task.

Revisioning files

To revision our assets we use the gulp-rev package:

$ yarn add -D gulp-rev

gulp-rev takes some files and creates revisioned versions by appending a hash based on the files content to it. It also creates a rev-manifest.json file with key-value pairs matching the original file names to the revisioned file names. This makes it easy referencing a static name, while still being able to use dynamic filenames for cache busting. Let's look into how we can get this working. First create a gulp rev tasks to take care of our revisions.

/* ------------------------------ * * Revision * */ gulp.task('rev', function (done) { const rev = require('gulp-rev') return gulp.src([ 'public/css/app.css', 'public/js/*.js', 'public/svgs/svg-sprite.svg' ], {base: 'public'}) .pipe(rev()) .pipe(gulp.dest('public')) .pipe(rev.manifest()) .pipe(gulp.dest('public')) })

We need to get all the files we want to revision. You should probably revision all assets you have, to make cache invalidation easier later on. Afterwards we pipe it through rev() and direct the output to wherever we want via gulp.dest. Than we can write the manifest with rev.manifest(). This will replace our old manifest with a new one.

Cleaning up

This is all fine, but we end up with all old revisions and new revisions in out public folder – not good. However, there is an easy fix, we can just read the rev-manifest.json and delete all files that are in it. This is preferable to deleting all files in all folders, because we might have some non-revisioned files in those folders as well. Of course we need to do this before we create the revisioned versions.

gulp.task('rev', function (done) { // synchronously delete old files if (fs.existsSync('public/rev-manifest.json')) { var manifest = fs.readFileSync('public/rev-manifest.json', 'utf8') del.sync(Object.values(JSON.parse(manifest)), {'cwd': 'public/'}) } // …

Original files

The code above takes care of old revisioned files, but the transformed files are still in our public folder.

Note: I am assuming your source files are in a different directory, e.g. resourecs/css/app.css and you have a task within your gulpfile which transforms those files, e.g. runs the css files through postcss and moves them to the public folder. If your files in public are the source files, do NOT add this step. However, you should always aim to have no files in public that are not put there during your build step.

First we need to install another package:

$ yarn add -D gulp-rev-delete-original

Afterwards you need to require it and pipe the stream through it after the rev step. Thats it, your directory should be nice an clean now.

gulp.task('rev', function (done) { const rev = require('gulp-rev') const revdel = require('gulp-rev-delete-original') // synchronously delete old files if (fs.existsSync('public/rev-manifest.json')) { var manifest = fs.readFileSync('public/rev-manifest.json', 'utf8') del.sync(Object.values(JSON.parse(manifest)), {'cwd': 'public/'}) } return gulp.src([ 'public/css/app.css', 'public/js/*.js', 'public/svgs/svg-sprite.svg' ], {base: 'public'}) .pipe(rev()) .pipe(gulp.dest('public')) .pipe(revdel()) .pipe(rev.manifest()) .pipe(gulp.dest('public')) })

Updating the html task

We have our nicely revisioned files, but we have to find a way to get them into out compiled templates, preferably without adding the hash manually. Luckily we have the rev-manifest.json, which we can read into a variable and add to the data object. Because most template engines do not allow / and . in variable names (and out keys have both), we need to do a little renaming when we add them.

gulp.task('html', function () { // load portfolio data let data = { 'portfolioItems': JSON.parse(fs.readFileSync('resources/templates/data/portfolio.json')) } // prepare files const files = JSON.parse(fs.readFileSync('public/rev-manifest.json', 'utf8')) Object.keys(files).map(function (key, index) { data[key.replace('.', '_').replace(/^[a-z]+\//, '')] = files[key] }) //...

After we have parsed the portfolio items, we load the rev-manifest.json file into a variable. Looping over the keys we remove the path and replace the . in the filename with a _. Afterwards we can append the entries to the data object. Of course, before this works we need to change the reference to the static filename of the assets with a mustache variable. For example instead of public/css/app.css we are now using /{app_css} in the head.mustache. Once this is done your gulp default task should deliver the same result as before.

In the next part of Building a Progressive web app we will be setting up a service worker to make our page faster and offline available.