loader.js

import { isBuiltin } from 'node:module'
import { dirname } from 'node:path'
import { promisify } from 'node:util'
import { fileURLToPath, pathToFileURL } from 'node:url'

import resolveCallback from 'resolve'
import { resolve as resolveTs, load } from 'ts-node/esm'
import { loadConfig, createMatchPath } from 'tsconfig-paths'

const resolveAsync = promisify(resolveCallback)
const tsExtensions = new Set(['.tsx', '.ts', '.mts', '.cts'])

const { absoluteBaseUrl, paths } = loadConfig()
const matchPath = createMatchPath(absoluteBaseUrl, paths)

async function resolve(specifier, ctx, defaultResolve) {
  const { parentURL = pathToFileURL(absoluteBaseUrl) } = ctx

  if (isBuiltin(specifier)) {
    return defaultResolve(specifier, ctx)
  }

  if (specifier.startsWith('file://')) {
    specifier = fileURLToPath(specifier)
  }

  let url
  try {
    const resolution = await resolveAsync(matchPath(specifier) || specifier, {
      basedir: dirname(fileURLToPath(parentURL)),
      // For whatever reason, --experimental-specifier-resolution=node doesn't search for .mjs extensions
      // but it does search for index.mjs files within directories
      extensions: ['.js', '.json', '.node', '.mjs', ...tsExtensions],
    })
    url = pathToFileURL(resolution).href
  } catch (error) {
    if (error.code === 'MODULE_NOT_FOUND') {
      // Match Node's error code
      error.code = 'ERR_MODULE_NOT_FOUND'
    }
    throw error
  }

  return resolveTs(url, ctx, defaultResolve)
}

export { resolve, load }