babelTransform.js

const { transformAsync } = require('@babel/core')

const babelPluginWcHmr = require('./babelPluginWcHmr.js')
const { createError } = require('../utils.js')

/** @typedef {import('./babelPluginWcHmr').BabelPluginWcHmrOptions} BabelPluginWcHmrOptions */

/**
 * @param {string} code
 * @param {string} filename
 * @param {BabelPluginWcHmrOptions} options
 * @return {Promise<import('@babel/core').BabelFileResult>}
 */
async function babelTransform(code, filename, options) {
  const largeFile = code.length > 100000
  const result = await transformAsync(code, {
    caller: {
      name: '@open-wc/dev-server-hmr',
      supportsStaticESM: true,
    },
    plugins: [
      [babelPluginWcHmr, options],
      require.resolve('@babel/plugin-syntax-class-properties'),
      [
        require.resolve('@babel/plugin-syntax-import-attributes'),
        { deprecatedAssertSyntax: true }, // See: https://babeljs.io/docs/v8-migration#babelplugin-syntax-import-assertions
      ],
      require.resolve('@babel/plugin-syntax-top-level-await'),
    ],
    filename,
    babelrc: false,
    configFile: false,
    compact: largeFile,
    sourceType: 'module',
    sourceMaps: true,
  })

  if (!result || !result.code) {
    throw createError(`Failed to babel transform ${filename}`)
  }

  return result
}

module.exports = { babelTransform }