esbuild-skypack-resolver/src/skypack-resolver.ts

A plugin to resolve package names to Skypack CDN URLs

// @ts-ignore
import { getDependencies } from './package.ts';
// @ts-ignore
import { cdn } from './cdn.ts';
// @ts-ignore
import { newPromiseResolve, PromiseResolve } from './util.ts';
import { OnResolveResult, Plugin, PluginBuild } from 'esbuild';

const PACKAGE_LOCK_FILE = `${process.cwd()}/package-lock.json`;
const PACKAGE_ID_REGEX = /^@?(([a-z0-9]+-?)+\/?)+$/;

interface Pending {
    [path: string]: PromiseResolve;
}

interface Cache {
    [path: string]: string;
}

/**
 * Creates new Skypack resolver plugin
 */
export function skypackResolver(packageLockFile = PACKAGE_LOCK_FILE): Plugin {
    const pending: Pending = {};
    const cache: Cache = {};

    return {
        name: 'skypack-resolver',
        async setup(build: PluginBuild) {
            const dependencies = await getDependencies(packageLockFile);

            build.onResolve({ filter: PACKAGE_ID_REGEX }, async ({ path }): Promise<OnResolveResult> => {
                if (pending[path]) {
                    await pending[path].promise;
                }

                if (path in cache) {
                    return { path: cache[path], external: true };
                }

                pending[path] = newPromiseResolve();

                const version = dependencies[path];
                const url = await cdn.getUrl(path, version);

                cache[path] = url;
                pending[path].resolve(null);

                return { path: url, external: true };
            });
        },
    };
}