deno_sync_module.ts

#!/usr/bin/env  -S deno run --unstable --allow-read --allow-write --allow-run --allow-net
import { ensureDirSync } from "https://deno.land/std@0.123.0/fs/mod.ts";
import { join } from "https://deno.land/std@0.123.0/path/mod.ts";
import pLimit from "https://cdn.skypack.dev/p-limit@v4.0.0";

function readJson(file: string) {
  const jsonString = Deno.readTextFileSync(file);
  const json = JSON.parse(jsonString);
  return json;
}

function denoCache(file: string) {
  return Deno.run({ cmd: [Deno.execPath(), "cache", file] }).status();
}

async function hasDefaultExport(url: string) {
  const code = `import __default from "${url}";`;
  const p = Deno.run({
    cmd: [Deno.execPath(), "eval", code],
    stdout: "piped",
    stderr: "piped",
  });
  await p.status();
  const stderr = new TextDecoder().decode(await p.stderrOutput());
  return stderr.indexOf("does not provide an export named 'default'") === -1;
}

// start actual code

const limit = pLimit(4);

const __dirname = new URL(".", import.meta.url).pathname;
const dirname = "deno_modules";
const target = join(__dirname, dirname);
const extension = ".ts";
const importMap = await readJson("./import_map.json");

// create all files and update cache
// TODO: handle remove, and compare hash before updating
const entries = Object.entries(importMap.imports).map(([key, value]) =>
  limit(async () => {
    const name = `${key}${extension}`;
    const filepath = join(target, name);
    console.log(`processing ${filepath}`);
    ensureDirSync(target);
    const withDefault = await hasDefaultExport(value as string);
    const source = !withDefault
      ? `export * from "${value}";
`
      : `export * from "${value}";
import ${key} from "${value}";
export default ${key};
`;
    Deno.writeTextFileSync(filepath, source);
    await denoCache(filepath);
  })
);

await Promise.all(entries);