vector-im-hydrogen-web/scripts/build-plugins/sw-dev.js

/*
Copyright 2025 New Vector Ltd.
Copyright 2024 The Matrix.org Foundation C.I.C.

SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE files in the repository root for full details.
*/

import fs from "fs/promises";
import path from "path";

/**
 * This rollup plugin makes it possible to use the serviceworker with the dev server.
 * The service worker is located in `/src/platform/web/sw.js` and it contains some
 * fields that need to be replaced with sensible values.
 *
 * We have a plugin that does this during build (see `./service-worker.js`).
 * This plugin does more or less the same but for dev.
 */

export function transformServiceWorkerInDevServer() {
    // See https://vitejs.dev/config/shared-options.html#define
    // Comes from vite.config.js
    let define;

    return {
        name: "hydrogen:transformServiceWorkerInDevServer",
        apply: "serve",
        enforce: "pre",

        configResolved(resolvedConfig) {
            // store the resolved config
            define = resolvedConfig.define;
        },

        async load(id) {
            if (!id.includes("sw.js")) return null;
            let code = await readServiceWorkerCode();
            for (const [key, value] of Object.entries(define)) {
                code = code.replaceAll(key, value);
            }
            return code;
        },
    };
}

/**
 * Read service worker code from `src/platform/web/sw.js`
 * @returns code as string
 */
async function readServiceWorkerCode() {
    const resolvedLocation = path.resolve(
        __dirname,
        "../../",
        "./src/platform/web/sw.js"
    );
    const data = await fs.readFile(resolvedLocation, { encoding: "utf-8" });
    return data;
}