django-webpack-loader 2.0.1

Transparently use webpack with django

django-webpack-loader

Use webpack to generate your static bundles without django's staticfiles or opaque wrappers.

Django webpack loader consumes the output generated by webpack-bundle-tracker and lets you use the generated bundles in django.

A changelog is also available.

Compatibility

Test cases cover Django>=2.0 on Python>=3.5. 100% code coverage is the target so we can be sure everything works anytime. It should probably work on older version of django as well but the package does not ship any test cases for them.

Install

npm install --save-dev webpack-bundle-tracker

pip install django-webpack-loader

Configuration

Configuring webpack-bundle-tracker

Before configuring django-webpack-loader, let's first configure what's necessary on webpack-bundle-tracker side. Update your Webpack configuration file (it's usually on webpack.config.js in the project root). Make sure your file looks like this (adapt to your needs):

const path = require('path');
const webpack = require('webpack');
const BundleTracker = require('webpack-bundle-tracker');

module.exports = {
  context: __dirname,
  entry: './assets/js/index',
  output: {
    path: path.resolve('./assets/webpack_bundles/'),
    filename: "[name]-[hash].js"
  },
  plugins: [
    new BundleTracker({path: __dirname, filename: 'webpack-stats.json'})
  ],
}

The configuration above expects the index.js (the app entrypoint file) to live inside the /assets/js/ directory (this guide going forward will assume that all front-end related files are placed inside the /assets/ directory, with the different kinds of files arranged within its subdirectories).

The generated compiled files will be placed inside the /assets/webpack_bundles/ directory and the file with the information regarding the bundles and assets (webpack-stats.json) will be stored in the project root.

Compiling the front-end assets

You must generate the front-end bundle using webpack-bundle-tracker before using django-webpack-loader. You can compile the assets and generate the bundles by running:

npx webpack --config webpack.config.js --watch

This will also generate the stats file. You can also refer to how django-react-boilerplate configure the package.json scripts for different situations.

⚠️ Hot reload is available through a specific config. Check this section.

⚠️ This is the recommended usage for the development environment. For usage in production, please refer to this section

Configuring the settings file

First of all, add webpack_loader to INSTALLED_APPS.

INSTALLED_APPS = (
  ...
  'webpack_loader',
  ...
)

Below is the recommended setup for the Django settings file when using django-webpack-loader.

WEBPACK_LOADER = {
  'DEFAULT': {
    'CACHE': not DEBUG,
    'STATS_FILE': os.path.join(BASE_DIR, 'webpack-stats.json'),
    'POLL_INTERVAL': 0.1,
    'IGNORE': [r'.+\.hot-update.js', r'.+\.map'],
  }
}

For that setup, we're using the DEBUG variable provided by Django. Since in a production environment (DEBUG = False) the assets files won't constantly change, we can safely cache the results (CACHE=True) and optimize our flow, as django-webpack-loader will read the stats file only once and store the assets files paths in memory. From that point onwards, it will use these stored paths as the source of truth. If CACHE=False, we'll always read the stats file to get the assets paths.

⚠️ If CACHE=True, any changes made in the assets files will only be read when the web workers are restarted.

During development, when the stats file changes a lot, we want to always poll for its updated version (in our case, we'll fetch it every 0.1s, as defined on POLL_INTERVAL).

⚠️ In production (DEBUG=False), we'll only fetch the stats file once, so POLL_INTERVAL is ignored.

While CACHE isn't directly related to POLL_INTERVAL, it's interesting to keep CACHE binded to the DEBUG logic value (in this case, the negation of the logic value) in order to only cache the assets in production, as we'd not continuously poll the stats file in that environment.

The STATS_FILE parameter represents the output file produced by webpack-bundle-tracker. Since in the Webpack configuration file we've named it webpack-stats.json and stored it on the project root, we must replicate that setting on the back-end side.

IGNORE is a list of regular expressions. If a file generated by Webpack matches one of the expressions, the file will not be included in the template.

Extra settings

• TIMEOUT is the number of seconds webpack_loader should wait for webpack to finish compiling before raising an exception. 0, None or leaving the value out of settings disables timeouts

• INTEGRITY is flag enabling Subresource Integrity on rendered <script> and <link> tags. Integrity hash is get from stats file and configuration on side of BundleTracker, where configuration option integrity: true is required.

• LOADER_CLASS is the fully qualified name of a python class as a string that holds the custom webpack loader. This is where behavior can be customized as to how the stats file is loaded. Examples include loading the stats file from a database, cache, external url, etc. For convenience, webpack_loader.loader.WebpackLoader can be extended. The load_assets method is likely where custom behavior will be added. This should return the stats file as an object.

• SKIP_COMMON_CHUNKS is a flag which prevents already generated chunks from being included again in the same page. This should only happen if you use more than one entrypoint per Django template (multiple render_bundle calls). By enabling this, you can get the same default behavior of the HtmlWebpackPlugin. The same caveats apply as when using skip_common_chunks on render_bundle, see that section below for more details.

Here's a simple example of loading from an external url:

import requests
from webpack_loader.loader import WebpackLoader

class ExternalWebpackLoader(WebpackLoader):
  def load_assets(self):
    url = self.config['STATS_URL']
    return requests.get(url).json()

Rendering

In order to render the front-end code into the Django templates, we use the render_bundle template tag.

Its behavior is to accept a string with the name of an entrypoint from the stats file (in our case, we're using main, which is the default) and it'll proceed to include all files under that entrypoint. You can read more about the entrypoints concept here.

⚠️ You can also check an example on how to use multiple entry values here.

Below is the basic usage for render_bundle within a template:

{% load render_bundle from webpack_loader %}

{% render_bundle 'main' %}

That will render the proper <script> and <link> tags needed in your template.

Running in development

For django-webpack-loader to work, you must run the webpack pipeline. Please refer to this section.

In summary, you should do the following:

# in one shell
npx webpack --config webpack.config.js --watch

# in another shell
python manage.py runserver

⚠️ You can also check this example on how to run a project with django-webpack-loader and webpack-bundle-track.

Usage in production

We recommend that you keep your local bundles and the stats file outside the version control, having a production pipeline that will compile and collect the assets during the deployment phase.

You must add STATICFILES_DIRS to your settings file, pointing to the directory where the static files are located. This will let collectstatic know where it should look at:

STATICFILES_DIRS = (
  os.path.join(BASE_DIR, 'assets'),
)

Below are the commands that should be run to compile and collect the static files (please note this may change from platform to platform):

npm run build
python manage.py collectstatic --noinput

First we build the assets and, since we have webpack-bundle-tracker in our front-end building pipeline, the stats file will be populated. Then, we manually run collecstatic to collect the compiled assets.

⚠️ Heroku is one platform that automatically runs collectstatic for you, so you need to set DISABLE_COLLECTSTATIC=1 environment var. Instead, you must manually run collectstatic after running webpack. In Heroku, this is achieved with a post_compile hook. You can see an example on how to implement this flow on django-react-boilerplate.

However, production usage for this package is fairly flexible. Other approaches may include keeping the production bundles in the version control and take that responsibility from the automatic pipeline. However, you must remember to always build the frontend and generate the bundle before pushing to remote.

Usage in tests

To run tests where render_bundle shows up, since we don't have webpack-bundle-tracker at that point to generate the stats file, the calls to render the bundle will fail. The solution is to use the FakeWebpackLoader in your test settings:

WEBPACK_LOADER['DEFAULT']['LOADER_CLASS'] = 'webpack_loader.loader.FakeWebpackLoader'

Advanced Usage

Rendering by file extension

render_bundle also takes a second argument which can be a file extension to match. This is useful when you want to render different types for files in separately. For example, to render CSS in head and JS at bottom we can do something like this,

{% load render_bundle from webpack_loader %}

<html>
  <head>
    {% render_bundle 'main' 'css' %}
  </head>
  <body>
    ....
    {% render_bundle 'main' 'js' %}
  </body>
</head>

Using preload

The is_preload=True option in the render_bundle template tag can be used to add rel="preload" link tags.

{% load render_bundle from webpack_loader %}

<html>
  <head>
    {% render_bundle 'main' 'css' is_preload=True %}
    {% render_bundle 'main' 'js' is_preload=True %}

    {% render_bundle 'main' 'css' %}
  </head>

  <body>
    {% render_bundle 'main' 'js' %}
  </body>
</html>

Accessing other webpack assets

webpack_static template tag provides facilities to load static assets managed by webpack in Django templates. It is like Django's built in static tag but for webpack assets instead.

In the below example, logo.png can be any static asset shipped with any npm package.

{% load webpack_static from webpack_loader %}

<!-- render full public path of logo.png -->
<img src="{% webpack_static 'logo.png' %}"/>

The public path is based on webpack.config.js output.publicPath.

Please note that this approach will use the original asset file, and not a post-processed one from the Webpack pipeline, in case that file had gone through such flow (i.e.: You've imported an image on the React side and used it there, the file used within the React components will probably have a hash string on its name, etc. This processed file will be different than the one you'll grab with webpack_static).

Use skip_common_chunks on render_bundle

You can use the parameter skip_common_chunks=True or skip_common_chunks=False to override the global SKIP_COMMON_CHUNKS setting for a specific bundle.

In order for this option to work, django-webpack-loader requires the request object to be in the context, to be able to keep track of the generated chunks.

The request object is passed by default via the django.template.context_processors.request middleware with using the Django built-in templating system, and also with using Jinja2.

If you don't have request in the context for some reason (e.g. using Template.render or render_to_string directly without passing the request), you'll get warnings on the console and the common chunks will remain duplicated.

Appending file extensions

The suffix option can be used to append a string at the end of the file URL. For instance, it can be used if your webpack configuration emits compressed .gz files. qwe

{% load render_bundle from webpack_loader %}
<html>
  <head>
    <meta charset="UTF-8">
    <title>Example</title>
    {% render_bundle 'main' 'css' %}
  </head>
  <body>
    {% render_bundle 'main' 'js' suffix='.gz' %}
  </body>
</html>

Multiple Webpack configurations

Version 1.0 and up of django-webpack-loader also supports multiple Webpack configurations. The following configuration defines 2 Webpack stats files in settings and uses the config argument in the template tags to influence which stats file to load the bundles from.

WEBPACK_LOADER = {
    'DEFAULT': {
        'BUNDLE_DIR_NAME': 'bundles/',
        'STATS_FILE': os.path.join(BASE_DIR, 'webpack-stats.json'),
    },
    'DASHBOARD': {
        'BUNDLE_DIR_NAME': 'dashboard_bundles/',
        'STATS_FILE': os.path.join(BASE_DIR, 'webpack-stats-dashboard.json'),
    }
}

{% load render_bundle from webpack_loader %}

<html>
  <body>
    ....
    {% render_bundle 'main' 'js' 'DEFAULT' %}
    {% render_bundle 'main' 'js' 'DASHBOARD' %}

    <!-- or render all files from a bundle -->
    {% render_bundle 'main' config='DASHBOARD' %}

    <!-- the following tags do the same thing -->
    {% render_bundle 'main' 'css' 'DASHBOARD' %}
    {% render_bundle 'main' extension='css' config='DASHBOARD' %}
    {% render_bundle 'main' config='DASHBOARD' extension='css' %}

    <!-- add some extra attributes to the tag -->
    {% render_bundle 'main' 'js' 'DEFAULT' attrs='async charset="UTF-8"'%}
  </body>
</head>

File URLs instead of html tags

If you need the URL to an asset without the HTML tags, the get_files template tag can be used. A common use case is specifying the URL to a custom css file for a Javascript plugin.

get_files works exactly like render_bundle except it returns a list of matching files and lets you assign the list to a custom template variable.

Each object in the returned list has 2 properties:

1. name, which is the name of a chunk from the stats file;
2. url, which can be:
3. The publicPath if the asset has one;
4. The path to the asset in the static files storage, if the asset doesn't have a publicPath.

For example:

{% load get_files from webpack_loader %}

{% get_files 'editor' 'css' as editor_css_files %}
CKEDITOR.config.contentsCss = '{{ editor_css_files.0.url }}';

<!-- or list down name and url for every file -->
<ul>
{% for css_file in editor_css_files %}
    <li>{{ css_file.name }} : {{ css_file.url }}</li>
{% endfor %}
</ul>

Code splitting

In case you wish to use code-splitting, follow the recipe below on the Javascript side.

Create your entrypoint file and add elements to the DOM, while leveraging the lazy imports.

// src/principal.js
function getComponent() {
  return import(/* webpackChunkName: "lodash" */ 'lodash').then(({ default: _ }) => {
    const element = document.createElement('div');

    element.innerHTML = _.join(['Hello', 'webpack'], ' ');

    return element;
  }).catch(error => 'An error occurred while loading the component');
}

getComponent().then((component) => {
  document.body.appendChild(component);
})

On your configuration file, do the following:

// webpack.config.js
module.exports = {
  context: __dirname,
  entry: {
    principal: './src/principal',
  },
  output: {
    path: path.resolve('./dist/'),
    // publicPath should match your STATIC_URL config.
    // This is required otherwise webpack will try to fetch 
    // our chunk generated by the dynamic import from "/" instead of "/dist/".
    publicPath: '/dist/', 
    chunkFilename: '[name].bundle.js',
    filename: "[name]-[hash].js"
  },
  plugins: [
    new BundleTracker({ path: __dirname, filename: 'webpack-stats.json' })
  ]
}

If you're using Webpack 5 instead of 4, do the following:

• Change filename: "[name]-[hash].js" to filename: "[name]-[fullhash].js";
• Remove /* webpackChunkName: "lodash" */, which is not needed anymore.

On your template, render the bundle as usual:

<!-- index.html -->
{% load render_bundle from webpack_loader %}

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>My test page</title>
  </head>
  <body>
    <p>This is my page</p>

    {% render_bundle 'principal' 'js' %}
  </body>
</html>

Hot reload

In case you wish to enable hot reload for your project using django-webpack-loader and webpack-bundle-tracker, please check out this example, in particular how server.js and webpack.config.js are configured.

Jinja2 Configuration

If you need to output your assets in a jinja template, we provide a Jinja2 extension that's compatible with django-jinja.

To install the extension, add it to the TEMPLATES configuration in the ["OPTIONS"]["extension"] list.

from django_jinja.builtins import DEFAULT_EXTENSIONS
TEMPLATES = [
  {
    "BACKEND": "django_jinja.backend.Jinja2",
    "OPTIONS": {
      "extensions": DEFAULT_EXTENSIONS + [
        "webpack_loader.contrib.jinja2ext.WebpackExtension",
      ],
    }
  }
]

Then in your base jinja template, do:

{{ render_bundle('main') }}

Migrating from version < 1.0.0

In order to use django-webpack-loader>=1.0.0, you must ensure that webpack-bundle-tracker@1.0.0 is being used on the JavaScript side. It's recommended that you always keep at least minor version parity across both packages, for full compatibility.

This is necessary because the formatting of webpack-stats.json that webpack-bundle-tracker outputs has changed starting at version 1.0.0-alpha.1. Starting at django-webpack-loader==1.0.0, this is the only formatting accepted here, meaning that other versions of that package don't output compatible files anymore, thereby breaking compatibility with older webpack-bundle-tracker releases.

Commercial Support

This project is maintained by Vinta Software and is used in products of Vinta's clients. We are always looking for exciting work, so if you need any commercial support, feel free to get in touch: [e-mail]