From 4f97d8fabda142685e36391da2c37c7e09955ac6 Mon Sep 17 00:00:00 2001
From: charlesroelli <3193168+charlesroelli@users.noreply.github.com>
Date: Thu, 1 Sep 2022 21:14:07 +0200
Subject: [PATCH] Document how to extract CSS, SVG for strict CSP (#36587)

* Webpack: explain how to extract CSS from bundle

* Webpack: explain how to extract SVG from bundle

* Update webpack.md

Co-authored-by: Mark Otto <otto@github.com>
---
 site/content/docs/5.2/customize/overview.md   |  2 +-
 .../docs/5.2/getting-started/webpack.md       | 87 +++++++++++++++++++
 2 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/site/content/docs/5.2/customize/overview.md b/site/content/docs/5.2/customize/overview.md
index 1b332bfe4671..d0a853cd6862 100644
--- a/site/content/docs/5.2/customize/overview.md
+++ b/site/content/docs/5.2/customize/overview.md
@@ -48,4 +48,4 @@ Several Bootstrap components include embedded SVGs in our CSS to style component
 - [Navbar toggle buttons]({{< docsref "/components/navbar#responsive-behaviors" >}})
 - [Select menus]({{< docsref "/forms/select" >}})
 
-Based on [community conversation](https://github.com/twbs/bootstrap/issues/25394), some options for addressing this in your own codebase include replacing the URLs with locally hosted assets, removing the images and using inline images (not possible in all components), and modifying your CSP. Our recommendation is to carefully review your own security policies and decide on the best path forward, if necessary.
+Based on [community conversation](https://github.com/twbs/bootstrap/issues/25394), some options for addressing this in your own codebase include [replacing the URLs with locally hosted assets]({{< docsref "/getting-started/webpack#extracting-svg-files" >}}), removing the images and using inline images (not possible in all components), and modifying your CSP. Our recommendation is to carefully review your own security policies and decide on the best path forward, if necessary.
diff --git a/site/content/docs/5.2/getting-started/webpack.md b/site/content/docs/5.2/getting-started/webpack.md
index ca104f98c1a5..86bab39eb919 100644
--- a/site/content/docs/5.2/getting-started/webpack.md
+++ b/site/content/docs/5.2/getting-started/webpack.md
@@ -230,6 +230,93 @@ Importing Bootstrap into Webpack requires the loaders we installed in the first
 
    Now you can start adding any Bootstrap components you want to use. Be sure to [check out the complete Webpack example project](https://github.com/twbs/examples/tree/main/webpack) for how to include additional custom Sass and optimize your build by importing only the parts of Bootstrap's CSS and JS that you need.
 
+## Production optimizations
+
+Depending on your setup, you may want to implement some additional security and speed optimizations useful for running the project in production. Note that these optimizations are not applied on [the Webpack example project](https://github.com/twbs/examples/tree/main/webpack) and are up to you to implement.
+
+### Extracting CSS
+
+The `style-loader` we configured above conveniently emits CSS into the bundle so that manually loading a CSS file in `dist/index.html` isn't necessary. This approach may not work with a strict Content Security Policy, however, and it may become a bottleneck in your application due to the large bundle size.
+
+To separate the CSS so that we can load it directly from `dist/index.html`, use the `mini-css-extract-loader` Webpack plugin.
+
+First, install the plugin:
+
+```sh
+npm install --save-dev mini-css-extract-plugin
+```
+
+Then instantiate and use the plugin in the Webpack configuration:
+
+```diff
+--- a/webpack/webpack.config.js
++++ b/webpack/webpack.config.js
+@@ -1,8 +1,10 @@
++const miniCssExtractPlugin = require('mini-css-extract-plugin')
+ const path = require('path')
+ 
+ module.exports = {
+   mode: 'development',
+   entry: './src/js/main.js',
++  plugins: [new miniCssExtractPlugin()],
+   output: {
+     filename: "main.js",
+     path: path.resolve(__dirname, "dist"),
+@@ -18,8 +20,8 @@ module.exports = {
+         test: /\.(scss)$/,
+         use: [
+           {
+-            // Adds CSS to the DOM by injecting a `<style>` tag
+-            loader: 'style-loader'
++            // Extracts CSS for each JS file that includes CSS
++            loader: miniCssExtractPlugin.loader
+           },
+           {
+```
+
+After running `npm run build` again, there will be a new file `dist/main.css`, which will contain all of the CSS imported by `src/js/main.js`. If you view `dist/index.html` in your browser now, the style will be missing, as it is now in `dist/main.css`. You can include the generated CSS in `dist/index.html` like this:
+
+```diff
+--- a/webpack/dist/index.html
++++ b/webpack/dist/index.html
+@@ -3,6 +3,7 @@
+   <head>
+     <meta charset="utf-8">
+     <meta name="viewport" content="width=device-width, initial-scale=1">
++    <link rel="stylesheet" href="./main.css">
+     <title>Bootstrap w/ Webpack</title>
+   </head>
+   <body>
+```
+
+### Extracting SVG files
+
+Bootstrap's CSS includes multiple references to SVG files via inline `data:` URIs. If you define a Content Security Policy for your project that blocks `data:` URIs for images, then these SVG files will not load. You can get around this problem by extracting the inline SVG files using Webpack's asset modules feature.
+
+Configure Webpack to extract inline SVG files like this:
+
+```diff
+--- a/webpack/webpack.config.js
++++ b/webpack/webpack.config.js
+@@ -16,6 +16,14 @@ module.exports = {
+   },
+   module: {
+     rules: [
++      {
++        mimetype: 'image/svg+xml',
++        scheme: 'data',
++        type: 'asset/resource',
++        generator: {
++          filename: 'icons/[hash].svg'
++        }
++      },
+       {
+         test: /\.(scss)$/,
+         use: [
+```
+
+After running `npm run build` again, you'll find the SVG files extracted into `dist/icons` and properly referenced from CSS.
+
 {{< markdown >}}
 {{< partial "guide-footer.md" >}}
 {{< /markdown >}}