Support `.ts` like cosmiconfig

[felipecrs]

• Refs https://github.com/cosmiconfig/cosmiconfig/pull/311

However, as Node 22.18+ now supports reading .ts by default, then maybe there is no need to depend on TypeScript.

[jimmy-guzman]

Might help others, I was able to add .ts support in userland by using jiti, something like:

import type { Loader } from "lilconfig";

import { lilconfig } from "lilconfig";

const loadTs: Loader = async (filepath) => {
  const { createJiti } = await import("jiti");

  return createJiti(import.meta.url, { interopDefault: true }).import(
    filepath,
    {
      default: true,
    },
  );
};

export async function loadConfig(name: string) {
  const explorer = lilconfig(name, {
    loaders: {
      ".mts": loadTs,
      ".ts": loadTs,
    },
    searchPlaces: [
      `${name}.config.ts`,
      `${name}.config.mts`,
    ],
  });

  return explorer.search(process.cwd());
}

Or without jiti

import { pathToFileURL } from "node:url";

import type { Loader } from "lilconfig";

import { lilconfig } from "lilconfig";

const loadTs: Loader = async (filepath) => {
  const url = pathToFileURL(filepath).href;
  const mod = await import(url);

  return mod.default ?? mod;
};

export async function loadConfig(name: string) {
  const explorer = lilconfig(name, {
    loaders: {
      ".mts": loadTs,
      ".ts": loadTs,
    },
    searchPlaces: [
      `${name}.config.ts`,
      `${name}.config.mts`,
    ],
  });

  return explorer.search(process.cwd());
}

[silverwind]

If process.features.typescript (v22.18.0+ or v22.6.0+ with flag) is truthy, await import could be attempted automatically if there is no existing loader configured for .ts or .mts.