index.js

import { existsSync, readFileSync, writeFileSync } from 'node:fs';
import { posix, dirname } from 'node:path';
import { execSync } from 'node:child_process';
import esbuild from 'esbuild';
import toml from '@iarna/toml';
import { fileURLToPath } from 'node:url';
import { getPlatformProxy } from 'wrangler';

/**
 * @typedef {{
 *   main: string;
 *   site: {
 *     bucket: string;
 *   }
 *   compatibility_flags?: string[];
 * }} WranglerConfig
 */

// list from https://developers.cloudflare.com/workers/runtime-apis/nodejs/
const compatible_node_modules = [
	'assert',
	'async_hooks',
	'buffer',
	'crypto',
	'diagnostics_channel',
	'events',
	'path',
	'process',
	'stream',
	'string_decoder',
	'util'
];

/** @type {import('./index.js').default} */
export default function ({ config = 'wrangler.toml', platformProxy = {} } = {}) {
	return {
		name: '@sveltejs/adapter-cloudflare-workers',

		async adapt(builder) {
			const { main, site, compatibility_flags } = validate_config(builder, config);

			const files = fileURLToPath(new URL('./files', import.meta.url).href);
			const tmp = builder.getBuildDirectory('cloudflare-workers-tmp');

			builder.rimraf(site.bucket);
			builder.rimraf(dirname(main));

			builder.log.info('Installing worker dependencies...');
			builder.copy(`${files}/_package.json`, `${tmp}/package.json`);

			// TODO would be cool if we could make this step unnecessary somehow
			const stdout = execSync('npm install', { cwd: tmp });
			builder.log.info(stdout.toString());

			builder.log.minor('Generating worker...');
			const relativePath = posix.relative(tmp, builder.getServerDirectory());

			builder.copy(`${files}/entry.js`, `${tmp}/entry.js`, {
				replace: {
					SERVER: `${relativePath}/index.js`,
					MANIFEST: './manifest.js'
				}
			});

			let prerendered_entries = Array.from(builder.prerendered.pages.entries());

			if (builder.config.kit.paths.base) {
				prerendered_entries = prerendered_entries.map(([path, { file }]) => [
					path,
					{ file: `${builder.config.kit.paths.base}/${file}` }
				]);
			}

			writeFileSync(
				`${tmp}/manifest.js`,
				`export const manifest = ${builder.generateManifest({ relativePath })};\n\n` +
					`export const prerendered = new Map(${JSON.stringify(prerendered_entries)});\n\n` +
					`export const base_path = ${JSON.stringify(builder.config.kit.paths.base)};\n`
			);

			const external = ['__STATIC_CONTENT_MANIFEST', 'cloudflare:*'];
			if (compatibility_flags && compatibility_flags.includes('nodejs_compat')) {
				external.push(...compatible_node_modules.map((id) => `node:${id}`));
			}

			try {
				const result = await esbuild.build({
					platform: 'browser',
					// https://github.com/cloudflare/workers-sdk/blob/a12b2786ce745f24475174bcec994ad691e65b0f/packages/wrangler/src/deployment-bundle/bundle.ts#L35-L36
					conditions: ['workerd', 'worker', 'browser'],
					sourcemap: 'linked',
					target: 'es2022',
					entryPoints: [`${tmp}/entry.js`],
					outfile: main,
					bundle: true,
					external,
					alias: Object.fromEntries(compatible_node_modules.map((id) => [id, `node:${id}`])),
					format: 'esm',
					loader: {
						'.wasm': 'copy',
						'.woff': 'copy',
						'.woff2': 'copy',
						'.ttf': 'copy',
						'.eot': 'copy',
						'.otf': 'copy'
					},
					logLevel: 'silent'
				});

				if (result.warnings.length > 0) {
					const formatted = await esbuild.formatMessages(result.warnings, {
						kind: 'warning',
						color: true
					});

					console.error(formatted.join('\n'));
				}
			} catch (error) {
				for (const e of error.errors) {
					for (const node of e.notes) {
						const match =
							/The package "(.+)" wasn't found on the file system but is built into node/.exec(
								node.text
							);

						if (match) {
							node.text = `Cannot use "${match[1]}" when deploying to Cloudflare.`;
						}
					}
				}

				const formatted = await esbuild.formatMessages(error.errors, {
					kind: 'error',
					color: true
				});

				console.error(formatted.join('\n'));

				throw new Error(
					`Bundling with esbuild failed with ${error.errors.length} ${
						error.errors.length === 1 ? 'error' : 'errors'
					}`
				);
			}

			builder.log.minor('Copying assets...');
			const bucket_dir = `${site.bucket}${builder.config.kit.paths.base}`;
			builder.writeClient(bucket_dir);
			builder.writePrerendered(bucket_dir);
		},

		async emulate() {
			const proxy = await getPlatformProxy(platformProxy);
			const platform = /** @type {App.Platform} */ ({
				env: proxy.env,
				context: proxy.ctx,
				caches: proxy.caches,
				cf: proxy.cf
			});

			/** @type {Record<string, any>} */
			const env = {};
			const prerender_platform = /** @type {App.Platform} */ (/** @type {unknown} */ ({ env }));

			for (const key in proxy.env) {
				Object.defineProperty(env, key, {
					get: () => {
						throw new Error(`Cannot access platform.env.${key} in a prerenderable route`);
					}
				});
			}

			return {
				platform: ({ prerender }) => {
					return prerender ? prerender_platform : platform;
				}
			};
		}
	};
}

/**
 * @param {import('@sveltejs/kit').Builder} builder
 * @param {string} config_file
 * @returns {WranglerConfig}
 */
function validate_config(builder, config_file) {
	if (existsSync(config_file)) {
		/** @type {WranglerConfig} */
		let wrangler_config;

		try {
			wrangler_config = /** @type {WranglerConfig} */ (
				toml.parse(readFileSync(config_file, 'utf-8'))
			);
		} catch (err) {
			err.message = `Error parsing ${config_file}: ${err.message}`;
			throw err;
		}

		if (!wrangler_config.site?.bucket) {
			throw new Error(
				`You must specify site.bucket in ${config_file}. Consult https://developers.cloudflare.com/workers/platform/sites/configuration`
			);
		}

		if (!wrangler_config.main) {
			throw new Error(
				`You must specify main option in ${config_file}. Consult https://github.com/sveltejs/kit/tree/main/packages/adapter-cloudflare-workers`
			);
		}

		return wrangler_config;
	}

	builder.log.error(
		'Consult https://developers.cloudflare.com/workers/platform/sites/configuration on how to setup your site'
	);

	builder.log(
		`
		Sample wrangler.toml:

		name = "<your-site-name>"
		account_id = "<your-account-id>"

		main = "./.cloudflare/worker.js"
		site.bucket = "./.cloudflare/public"

		build.command = "npm run build"

		compatibility_date = "2021-11-12"
		workers_dev = true`
			.replace(/^\t+/gm, '')
			.trim()
	);

	throw new Error(`Missing a ${config_file} file`);
}