`Exception during run: Error [ERR_REQUIRE_ESM]: Must use import to load ES Module:`

[khteh]

I don't have any require() in my code but still hit the following error:

$ ./node_modules/.bin/mocha -r ts-node/register tests/**/*.ts --reporter mocha-junit-reporter --reporter-options mochaFile=test_reports/mocha/test-results.xml --exit
(node:1015864) ExperimentalWarning: `--experimental-loader` may be removed in the future; instead use `register()`:
--import 'data:text/javascript,import { register } from "node:module"; import { pathToFileURL } from "node:url"; register("ts-node/esm", pathToFileURL("./"));'
(Use `node --trace-warnings ...` to show where the warning was created)
(node:1015864) [DEP0180] DeprecationWarning: fs.Stats constructor is deprecated.
(Use `node --trace-deprecation ...` to show where the warning was created)

 Exception during run: Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /usr/src/Node.JS/Node.JSRestAPI/tests/IntegrationTests/add_students_to_teacher_tests.ts
require() of ES modules is not supported.
require() of /usr/src/Node.JS/Node.JSRestAPI/tests/IntegrationTests/add_students_to_teacher_tests.ts from /usr/src/Node.JS/Node.JSRestAPI/node_modules/mocha/lib/nodejs/esm-utils.js is an ES module file as it is a .ts file whose nearest parent package.json contains "type": "module" which defines all .ts files in that package scope as ES modules.
Instead change the requiring code to use import(), or remove "type": "module" from /usr/src/Node.JS/Node.JSRestAPI/package.json.

    at createErrRequireEsm (/usr/src/Node.JS/Node.JSRestAPI/node_modules/ts-node/dist-raw/node-internal-errors.js:46:15)
    at assertScriptCanLoadAsCJSImpl (/usr/src/Node.JS/Node.JSRestAPI/node_modules/ts-node/dist-raw/node-internal-modules-cjs-loader.js:584:11)
    at Object.require.extensions.<computed> [as .ts] (/usr/src/Node.JS/Node.JSRestAPI/node_modules/ts-node/src/index.ts:1610:5)
    at Module.load (node:internal/modules/cjs/loader:1479:32)
    at Module._load (node:internal/modules/cjs/loader:1298:12)
    at TracingChannel.traceSync (node:diagnostics_channel:328:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:244:24)
    at Module.require (node:internal/modules/cjs/loader:1502:12)
    at require (node:internal/modules/helpers:152:16)
    at Object.requireModule [as requireOrImport] (/usr/src/Node.JS/Node.JSRestAPI/node_modules/mocha/lib/nodejs/esm-utils.js:98:12)
    at Object.exports.loadFilesAsync (/usr/src/Node.JS/Node.JSRestAPI/node_modules/mocha/lib/nodejs/esm-utils.js:152:34)
    at Mocha.loadFilesAsync (/usr/src/Node.JS/Node.JSRestAPI/node_modules/mocha/lib/mocha.js:429:19)
    at singleRun (/usr/src/Node.JS/Node.JSRestAPI/node_modules/mocha/lib/cli/run-helpers.js:168:15)
    at exports.runMocha (/usr/src/Node.JS/Node.JSRestAPI/node_modules/mocha/lib/cli/run-helpers.js:245:10)
    at Object.exports.handler (/usr/src/Node.JS/Node.JSRestAPI/node_modules/mocha/lib/cli/run.js:379:11)
    at /usr/src/Node.JS/Node.JSRestAPI/node_modules/yargs/build/index.cjs:1:8993
    at /usr/src/Node.JS/Node.JSRestAPI/node_modules/yargs/build/index.cjs:1:4949 {
  code: 'ERR_REQUIRE_ESM'
}

node v25.0.0
"typescript": "^5.9.3"
"mocha": "^11.7.4",

package.json:

"type": "module",

tsconfig.json:

  "node-option": [
    "loader=ts-node/esm"
  ],
 "compilerOptions": {
      "target": "ES2022",
      "module": "nodenext", 
      "moduleResolution": "nodenext",
      "types": ["mocha"],
 }

[RobinVdBroeck]

I think this is related to #5494

I've run into the same problem on my project, adding this to my mocha config fixed it:

"node-option": [
    "no-experimental-strip-types"
]

[khteh]

I just tried but to no avail.