CssModuleBundle

CssModuleBundle is a Symfony bundle that enables the use of CSS Modules and JavaScript module imports directly within Twig templates.

Sample:

/* button.module.scss */
.button {
    background-color: blue;
    color: white;
    padding: 10px 20px;
    border-radius: 5px;
    text-decoration: none;
}

{# Import the CSS module defined above #}
{% importModule 'button.module.scss' %}

{# Use a scoped class from the imported module by string #}
<a class="{{ scope('button') }}">Click me</a>

{# ...or by array #}
<a class="{{ scope(['button', 'button2']) }}">Click me</a>

🎯 Purpose

CSS Modules bring scoped class names to CSS, avoiding naming collisions and promoting modular architecture. This bundle brings the same benefits to Symfony + Twig.

If you're familiar with CSS Modules, particularly in React, you'll appreciate the ability to:

• Use short, unique class names without global conflicts.
• Keep styles encapsulated at the component level.
• Apply the same development patterns in Symfony projects with Twig.

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📦 Installation

composer require mak/css-module-bundle

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⚙️ Configuration

Webpack Encore Setup

In your webpack.config.js:

Encore
    // ...
    .addEntry('app', [
        './assets/app.js',
        ...glob.sync(["./templates/**/*.html.twig"]),
    ])
    .addLoader({
        test: /\.twig$/,
        use: [
            {
                loader: path.resolve(
                    __dirname,
                    "vendor/mak/css-module-bundle/Resources/webpack/TwigLoader.js"
                ),
            },
        ],
    })
    .configureCssLoader((options) => {
        options.modules = {
            auto: (resourcePath) => /\.module\.\w+$/i.test(resourcePath),
            localIdentName: "[hash:base64:5]",
        };
    })

Symfony Bundle Configuration

# config/packages/mak_css_module.yaml
mak_css_module:
    localIdentName: '[hash:base64]'
    localIdentContext: '%kernel.project_dir%'
    localIdentHashSalt: null

---

🚀 Usage in Twig

{# Import CSS module into the current template context #}
{% importModule 'button.module.scss' %}

{# Apply a scoped class from the imported module #}
<a class="{{ scope('button') }}">Click me</a>

{# Alternatively, specify the module explicitly #}
<a class="{{ scope('button', 'button.module.scss') }}">Click me</a>

⚠️ Note:
Imported modules only apply to the current template to prevent unintended side effects in included templates.

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🧱 Component-First Folder Structure

Inspired by Atomic Design and modern component-based development, you can colocate templates, styles, and JavaScript files:

templates/
├─ components/
│  ├─ atoms/
│  │  ├─ sample-atom/
│  │  │  ├─ sample-atom.html.twig
│  │  │  ├─ sample-atom.module.css
│  │  │  ├─ sample_atom_controller.js
│  ├─ molecules/
│  ├─ organisms/
├─ pages/
├─ base/

With importModule, CSS and JS are automatically bundled for each component.

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⚡ Stimulus Integration

To enable autoloading of Stimulus controllers in your templates:

// assets/bootstrap.js
app.load(
  definitionsFromContext(
    require.context(
      "@symfony/stimulus-bridge/lazy-controller-loader!../templates",
      true,
      /\.[jt]sx?$/
    )
  )
);

This allows Webpack to bundle Stimulus controllers alongside your Twig templates.

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🔍 Internals

• The bundle mimics Webpack’s css-loader functionality to hash class names.
• importModule registers the module within a template.
• scope() computes the hashed class name at compile time.
• Included templates are isolated to prevent shared scope.

⚠️ Note:
scope() accepts raw string input for class names. Input validation is out of scope.

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❓ Frequently Asked Questions

How to use Twig CSS Modules with PurifyCSS, UnCSS, or PurgeCSS?

These tools remove unused CSS by scanning for class names. Since CSS module hashes aren't explicitly written in Twig/JS, you must:

1. Add a prefix to all CSS module hashes:

mak_css_module:
  localIdentName: '_[hash:base64]'

2. Update your Encore config similarly.

3. Safelist the prefix in PurgeCSS:

new PurgeCSSPlugin({
    paths: glob.sync([
        `${PATHS.templates}/**/*.html.twig`,
        `${PATHS.assets}/**/*.{js,ts}`,
    ], { nodir: true }),
    safelist: {
        deep: [/^_/],
    },
    extractors: [
        {
            extractor: purgeHtml,
            extensions: ["html", "twig"],
        },
    ],
})

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Is there a performance impact?

No. All hashing is done at Twig compile time, so runtime performance is unaffected. In fact, shorter hashed class names may slightly improve render efficiency.

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How to use SASS, LESS, or other preprocessors?

No additional setup is needed. Just use .module.scss or .module.less as usual. Webpack will handle them according to your preprocessor loader configuration.

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Can I use global variables or mixins in CSS Modules?

Yes, using sass-resources-loader:

Encore
    .configureLoaderRule("scss", (loaderRule) => {
        loaderRule.oneOf.forEach((rule) => {
            rule.use.push({
                loader: "sass-resources-loader",
                options: {
                    resources: [
                        path.resolve(__dirname, "./node_modules/bootstrap5/scss/_mixins.scss"),
                        path.resolve(__dirname, "./assets/scss/global.scss"),
                    ],
                },
            });
        });
    });

This will inject shared mixins and variables into every .module.scss file.

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🙌 Contributing & Feedback

Pull requests are welcome! If you find bugs or have feature suggestions, feel free to open an issue or tweet about it using #css-modules-bundle.