SyntaxError: Cannot use import statement outside a module

[morganney]

While running Jest against tests for an ES module that uses astravel as a dependency, I encountered the following SyntaxError:

morgan@mactop magic-comments-loader (develop) $ npm run test:spec -- __tests__/loader.parser.spec.js 

> [email protected] test:spec
> NODE_OPTIONS='--loader=babel-register-esm --no-warnings --experimental-vm-modules' BABEL_ENV=test jest -c jest.config.spec.js __tests__/loader.parser.spec.js

 FAIL  __tests__/loader.parser.spec.js
  parser
    ✕ parses most complex constructs for dynamic imports (1393 ms)

parser > parses most complex constructs for dynamic imports
    [
      {
        moduleIdentifier: 'javascript/esm|/Users/morgan/code/magic-comments-loader/src/index.js!/Users/morgan/code/magic-comments-loader/__tests__/__fixtures__/complex.js',
        moduleName: './__fixtures__/complex.js',
        message: 'Module build failed (from ../src/index.js):\n' +
          '/Users/morgan/code/magic-comments-loader/node_modules/astravel/dist/module/astravel.js:1\n' +
          'import { defaultTraveler } from "./defaultTraveler.js";\n' +
          '^^^^^^\n' +
          '\n' +
          'SyntaxError: Cannot use import statement outside a module\n' +
          '    at internalCompileFunction (node:internal/vm:73:18)\n' +
          '    at wrapSafe (node:internal/modules/cjs/loader:1177:20)\n' +
          '    at Module._compile (node:internal/modules/cjs/loader:1221:27)\n' +
          '    at Module._extensions..js (node:internal/modules/cjs/loader:1311:10)\n' +
          '    at Module.load (node:internal/modules/cjs/loader:1115:32)\n' +
          '    at Module._load (node:internal/modules/cjs/loader:962:12)\n' +
          '    at ModuleWrap.<anonymous> (node:internal/modules/esm/translators:165:29)\n' +
          '    at ModuleJob.run (node:internal/modules/esm/module_job:192:25)\n' +
          '    at async CustomizedModuleLoader.import (node:internal/modules/esm/loader:246:24)\n' +
          '    at async parse (file:///Users/morgan/code/magic-comments-loader/src/util.js:838:41)',

morgan@mactop magic-comments-loader (develop) $ node -v
v20.3.1
morgan@mactop magic-comments-loader (develop) $ npm -v
9.7.2
morgan@mactop magic-comments-loader (develop) $ npm ls astravel
[email protected] /Users/morgan/code/magic-comments-loader
└── [email protected]

package.json

{
  "name": "magic-comments-loader",
  "version": "1.5.1",
  "description": "Add webpack magic comments to your dynamic imports at build time",
  "main": "dist",
  "type": "module",
  "exports": {
    ".": {
      "import": "./dist/index.js",
      "require": "./dist/cjs/index.cjs",
      "default": "./dist/index.js"
    },
    "./package.json": "./package.json"
  },
  "engines": {
    "node": ">=12.17.0"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/morganney/magic-comments-loader.git"
  },
  "bugs": {
    "url": "https://github.com/morganney/magic-comments-loader/issues"
  },
  "scripts": {
    "prepack": "npm run build",
    "build": "npm run build:esm && npm run build:cjs",
    "build:esm": "babel src --out-dir dist",
    "build:cjs": "BABEL_ENV=cjs babel src --out-dir dist/cjs --out-file-extension .cjs && node cjs.js",
    "lint": "eslint . src __tests__ --ext .js,.cjs",
    "lint:fix": "npm run lint -- --fix",
    "test:unit": "node --experimental-vm-modules --no-warnings ./node_modules/.bin/jest",
    "test:spec": "NODE_OPTIONS='--loader=babel-register-esm --no-warnings --experimental-vm-modules' BABEL_ENV=test jest -c jest.config.spec.js",
    "test": "npm run test:unit && npm run test:spec"
  },
  "keywords": [
    "webpack",
    "magic",
    "comments",
    "loader",
    "dynamic",
    "import"
  ],
  "author": "Morgan Ney <[email protected]>",
  "license": "MIT",
  "files": [
    "dist"
  ],
  "devDependencies": {
    "@babel/cli": "^7.22.5",
    "@babel/core": "^7.22.5",
    "@babel/eslint-parser": "^7.22.5",
    "@babel/preset-env": "^7.22.5",
    "babel-register-esm": "^1.2.4",
    "codecov": "^4.0.0-0",
    "eslint": "^8.42.0",
    "eslint-config-prettier": "^8.8.0",
    "eslint-plugin-jest": "^27.2.1",
    "eslint-plugin-prettier": "^4.2.0",
    "jest": "^29.5.0",
    "jest-light-runner": "^0.5.0",
    "memfs": "^4.0.0",
    "prettier": "^2.8.8",
    "webpack": "^5.87.0"
  },
  "dependencies": {
    "acorn": "^8.9.0",
    "acorn-jsx": "^5.3.2",
    "acorn-stage3": "^4.0.0",
    "astravel": "^0.6.1",
    "astring": "^1.8.6",
    "loader-utils": "^3.2.1",
    "micromatch": "^4.0.4",
    "schema-utils": "^4.1.0"
  }
}

jest.config.spec.js

export default {
  collectCoverage: true,
  collectCoverageFrom: ['**/src/**/*.js'],
  coverageProvider: 'babel',
  coverageReporters: ['text', 'text-summary'],
  modulePathIgnorePatterns: ['dist'],
  /**
   * Use alternative runner to circumvent segmentation fault when
   * webpack's node.js API uses dynamic imports while running
   * jest's v8 vm context code.
   *
   * @see https://github.com/nodejs/node/issues/35889
   * @see https://github.com/nodejs/node/issues/25424
   */
  runner: 'jest-light-runner',
  testMatch: ['**/__tests__/**/*.spec.js'],
  transform: {}
}

I've noticed that you provide ESM and CJS builds via conditional exports in your package.json file. I believe this error is because you do not include "type": "module" in your package.json file so that consumers attempting to load the ES variant of astravel from an ES module context trigger the exception.