Error [ERR_REQUIRE_ESM]: Must use import to load ES Module:

[khteh]

Prerequisites

• Checked that your issue hasn't already been filed by cross-referencing issues with the faq label
• Checked next-gen ES issues and syntax problems by using the same environment and/or transpiler configuration without Mocha to ensure it isn't just a feature that actually isn't supported in the environment in question or a bug in your code.
• 'Smoke tested' the code to be tested by running it outside the real test suite to get a better sense of whether the problem is in the code under test, your usage of Mocha, or Mocha itself
• Ensured that there is no discrepancy between the locally and globally installed versions of Mocha. You can find them with: node node_modules/.bin/mocha --version(Local) and mocha --version(Global). We recommend that you not install Mocha globally.

Description

Steps to Reproduce

run mocha <test_folder>

Expected behavior: [What you expect to happen]
No error
Actual behavior: [What actually happens]

>mocha tests
internal/modules/cjs/loader.js:1080
      throw new ERR_REQUIRE_ESM(filename, parentPath, packageJsonPath);
      ^

Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: C:\Projects\Node.js\Node.JSRestAPI\tests\greetingsapi_tests.js
require() of ES modules is not supported.
require() of C:\Projects\Node.js\Node.JSRestAPI\tests\greetingsapi_tests.js from C:\Users\funcoolgeek\AppData\Roaming\npm\node_modules\mocha\lib\mocha.js is an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which defines all .js files in that package scope as ES modules.
Instead rename greetingsapi_tests.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from C:\Projects\Node.js\Node.JSRestAPI\package.json.

    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1080:13)
    at Module.load (internal/modules/cjs/loader.js:928:32)
    at Function.Module._load (internal/modules/cjs/loader.js:769:14)
    at Module.require (internal/modules/cjs/loader.js:952:19)
    at require (internal/modules/cjs/helpers.js:88:18)
    at C:\Users\funcoolgeek\AppData\Roaming\npm\node_modules\mocha\lib\mocha.js:250:27
    at Array.forEach (<anonymous>)
    at Mocha.loadFiles (C:\Users\funcoolgeek\AppData\Roaming\npm\node_modules\mocha\lib\mocha.js:247:14)
    at Mocha.run (C:\Users\funcoolgeek\AppData\Roaming\npm\node_modules\mocha\lib\mocha.js:576:10)
    at Object.<anonymous> (C:\Users\funcoolgeek\AppData\Roaming\npm\node_modules\mocha\bin\_mocha:637:18)
    at Module._compile (internal/modules/cjs/loader.js:1063:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
    at Module.load (internal/modules/cjs/loader.js:928:32)
    at Function.Module._load (internal/modules/cjs/loader.js:769:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
    at internal/main/run_main_module.js:17:47 {
  code: 'ERR_REQUIRE_ESM'
}

Reproduces how often: [What percentage of the time does it reproduce?]

Versions

5.2.0

• The output of mocha --version and node node_modules/.bin/mocha --version: 5.2.0
• The output of node --version:
• Your operating system
  • name and version: Windows 10 AND container node:latest
  • architecture (32 or 64-bit): 64-bit
• Your shell (e.g., bash, zsh, PowerShell, cmd): bash
• Your browser and version (if running browser tests):
• Any third-party Mocha-related modules (and their versions):
• Any code transpiler (e.g., TypeScript, CoffeeScript, Babel) being used (and its version): javascript. Node.JS v14.16.0

Additional Information

[juergba]

Mocha supports Node's native ESM support since v7.1.0.

Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: C:\Projects\Node.js\Node.JSRestAPI\tests\greetingsapi_tests.js
require() of ES modules is not supported.

Please see Node docs esm.

[pr0t4zy]

I have this bug on mocha@9.1.3 (node v16.13.1):

Error [ERR_REQUIRE_ESM]: require() of ES Module module.test.mjs not supported.
Instead change the require of module.test.mjs to a dynamic import() which is available in all CommonJS modules.
    at /usr/local/lib/node_modules/mocha/lib/mocha.js:430:36
    at Array.forEach (<anonymous>)
    at Mocha.loadFiles (/usr/local/lib/node_modules/mocha/lib/mocha.js:427:14)
    at Mocha.run (/usr/local/lib/node_modules/mocha/lib/mocha.js:1028:10)

Doesn't it mean that Mocha tries to load the module with require()?

[juergba]

@pr0t4zy Probably yes, loadFiles() works synchronously and uses require.

In case you are using Mocha programmatically, you have to load your test files in an asynchronous way with loadFilesAsync().

[pr0t4zy]

I changed:

mocha.run(failures => {
  process.exitCode = failures ? 1 : 0;
});

to

mocha.loadFilesAsync()
  .then(() => mocha.run(failures => process.exitCode = failures ? 1 : 0))
  .catch(() => process.exitCode = 1);

And works like a charm.

Thank you for the support!