@lit-labs/ssr-dom-shim/register-css-hook.js

DOM shim for Lit Server Side Rendering (SSR)

/**
 * @license
 * Copyright 2024 Google LLC
 * SPDX-License-Identifier: BSD-3-Clause
 */
import { CSSStyleSheet } from './index.js';
try {
    // Detect whether the environment supports importing CSS files.
    const inlineCSS = 'data:text/css;base64,cHt0b3A6MDt9';
    const cssImportsSupported = await import(inlineCSS, { with: { type: 'css' } })
        .then(() => true)
        .catch(() => false);
    // Avoid breaking non-Node.js environments by checking for the
    // existance of register on the node:module import.
    const nodeModule = cssImportsSupported ? null : await import('node:module');
    if (nodeModule && 'register' in nodeModule.default) {
        // Register the CSSStyleSheet polyfill in the global scope
        // in order for the hook to pick it up correspondingly when generating
        // code for CSS imports.
        // This also avoid breaking the serialization in packages/reactive-element/src/css-tag.ts
        // as the symbol will be available in the global scrope on evaluation.
        globalThis.CSSStyleSheet ??= CSSStyleSheet;
        /**
         * This module registers a Node.js Hook for loading CSS
         * files as CSSStyleSheet instances.
         *
         * @example
         *
         * ```ts
         *  import styles from 'my-styles.css' with {type: 'css'};
         * ```
         *
         * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import/with
         * @see https://nodejs.org/api/module.html#customization-hooks
         */
        nodeModule.default.register('./lib/css-hook.js', {
            parentURL: import.meta.url,
        });
    }
}
catch {
    /* empty */
}
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