rollup-build-webext-config/index.ts

/* eslint-env node */

import {readFile} from 'node:fs/promises';
import {basename, dirname, extname, join, relative, resolve} from 'node:path';

import {type Plugin, type RollupOptions} from 'rollup';

import {getAssetEntrypoints, getScriptEntrypoints} from './entrypoints';

/**
 * Looks through a `manifest.json` file for Javascript entrypoints and other
 * assets, and returns an array of Rollup configuration. This configuration will
 * have each entrypoint processed as its own bundle, and will additionally
 * handle copying the manifest and other assets into the build output, as well
 * as any necessary path rewriting in the manifest itself.
 * @param options
 * @param options.manifest Path to the manifest file to be processed, relative
 * to the current working directory
 * @param options.outDir Directory path where build output will go
 * @param options.plugins Rollup plugins to be used when processing each
 * Javascript entry point
 * @param options.sourcemap Controls inclusion of sourcemaps in the output
 */
export async function buildConfig ({
	manifest: manifestPathRelative,
	outDir,
	plugins = [],
	sourcemap,
}: {
	manifest: string;
	outDir: string;
	plugins: Plugin[];
	sourcemap: boolean | 'inline' | 'hidden';
}): Promise<RollupOptions[]> {
	const manifestPath = resolve(process.cwd(), manifestPathRelative);
	const manifestDirname = dirname(manifestPath);

	// Load the manifest
	let manifestContent: chrome.runtime.Manifest;
	try {
		manifestContent = JSON.parse(await readFile(manifestPath, {encoding: 'utf-8'}));
	} catch (error) {
		throw new Error('Failed to load manifest');
	}

	// reserve manifest.json at the root of the build output - needs to be the
	// actual manifest file we generate
	const uniqueFileNameSegmentCache = new Map([['\0', 'manifest.json']]);
	function ensureUniquePath (filepath: string, ext = extname(filepath).slice(1)) {
		// TODO: this function is hell there's gotta be a better way to do literally
		//       all of this
		const cached = uniqueFileNameSegmentCache.get(filepath);
		if (cached) {
			return cached;
		}
		const idealName = join(dirname(filepath), basename(filepath, extname(filepath)));

		const buildName = (str: string, n: number) => n ? `${str}_${n}.${ext}` : `${str}.${ext}`;

		let uniquenessNum = 0;
		const existingNames = [...uniqueFileNameSegmentCache.values()];
		while (
			existingNames.some(existingName =>
				existingName.toLowerCase() === buildName(idealName, uniquenessNum).toLowerCase()
			)
		) {
			uniquenessNum += 1;
		}

		const finalName = buildName(idealName, uniquenessNum);
		uniqueFileNameSegmentCache.set(filepath, finalName);
		return finalName;
	}

	const scripts = getScriptEntrypoints(manifestContent);
	const assets = getAssetEntrypoints(manifestContent);

	return [
		// Process each script entrypoint independently
		...scripts.map(({path, replacePath}) => {
			// Figure out where this bundle will live in the output
			const outPath = ensureUniquePath(path, 'js');

			// Rewrite the manifest with that path
			replacePath(outPath);

			// Build the bundle
			return {
				input: relative(process.cwd(), join(manifestDirname, path)),
				output: {
					file: join(outDir, outPath),
					format: 'iife' as const,
					sourcemap,
				},
				plugins,
			};
		}),

		// Special step that processes the manifest and injects other assets
		{
			input: manifestPathRelative,
			output: {
				file: join(outDir, 'manifest.json'),
			},
			plugins: [
				{
					name: '_manifest-asset-processing',
					// emit other assets
					async buildStart () {
						await Promise.all(assets.map(async ({path, replacePath}) => {
							// Figure out where the asset will live in output
							const outPath = ensureUniquePath(path);

							// Rewrite the manifest with that path
							replacePath(outPath);

							// Emit the asset as part of the build step
							this.emitFile({
								type: 'asset',
								fileName: outPath,
								source: await readFile(join(manifestDirname, path)),
							});
						}));
					},

					// hacks to make sure the manifest is emitted as bare JSON
					load: id => id === manifestPath ? 'debugger;' : null,
					renderChunk: (_, chunk) =>
						chunk.facadeModuleId === manifestPath
							? JSON.stringify(manifestContent, null, '\t')
							: null,
				},
			],
		},
	];
}