ERR_UNKNOWN_FILE_EXTENSION when importing certain packages in tests

[patreeceeo]

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_modules/.bin/mocha --version(Local) and mocha --version(Global). We recommend that you not install Mocha globally.

Description

Similar, but not the same as, #4900. Nothing in there helped with my situation.

Mocha works fine until I import something (anything, apparently) from this particular package (@xrengine/engine) in my tests. When I do, and only when I do, I get this error:

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for .../Code/repo-mocha-issue/MathFunctions.test.ts

Steps to Reproduce

MCVE: https://github.com/patreeceeo/repro-mocha-issue

1. Clone the above
2. npm install
3. npm run test

Expected behavior: tests should run

Actual behavior: error

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /home/patrick/Code/repo-mocha-issue/MathFunctions.test.ts
    at new NodeError (node:internal/errors:363:5)
    at Loader.defaultGetFormat [as _getFormat] (node:internal/modules/esm/get_format:71:15)
    at Loader.getFormat (node:internal/modules/esm/loader:105:42)
    at Loader.getModuleJob (node:internal/modules/esm/loader:243:31)
    at async Loader.import (node:internal/modules/esm/loader:177:17)
    at async importModuleDynamicallyWrapper (node:internal/vm/module:437:15)
    at async formattedImport (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/nodejs/esm-utils.js:7:14)
    at async Object.exports.requireOrImport (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/nodejs/esm-utils.js:38:28)
    at async Object.exports.loadFilesAsync (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/nodejs/esm-utils.js:91:20)
    at async singleRun (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/cli/run-helpers.js:125:3)
    at async Object.exports.handler (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/cli/run.js:370:5)

Reproduces how often: 100%

Versions

• The output of mocha --version and node_modules/.bin/mocha --version: 10.1.0 (locally, no global install)
• The output of node --version: 16.3.0 / 18.12.1
• Your operating system
  • name and version: 5.15.0-50-generic 20.04.1-Ubuntu
  • architecture (32 or 64-bit): 64
• Your shell (e.g., bash, zsh, PowerShell, cmd): ZSH
• Your browser and version (if running browser tests): N/A
• Any third-party Mocha-related modules (and their versions): [email protected]
• Any code transpiler (e.g., TypeScript, CoffeeScript, Babel) being used (and its version): See above

[patreeceeo]

Also, I was running mocha with the debug flag set but didn't see anything helpful in there. So that might be a side issue. Here's the complete output:

> [email protected] test
> DEBUG=mocha:* mocha --config .mocharc.js

  mocha:cli:config loadConfig: trying to parse config at .mocharc.js +0ms
  mocha:cli:config parsers: load cwd-relative path: "/home/patrick/Code/repo-mocha-issue/.mocharc.js" +1ms
  mocha:cli:options no config found in /home/patrick/Code/repo-mocha-issue/package.json +0ms
  mocha:cli:mocha loaded opts {
  _: [ '**/*.test.ts' ],
  config: false,
  package: false,
  failZero: false,
  parallel: false,
  require: [ 'tests/mocha.env', 'ts-node/register' ],
  extension: [ 'ts' ],
  bail: true,
  exit: true,
  recursive: true,
  jobs: 1,
  timeout: '2000',
  ignore: [ 'node_modules/**' ],
  diff: true,
  reporter: 'spec',
  slow: 75,
  ui: 'bdd',
  'watch-ignore': [ 'node_modules', '.git' ]
} +0ms
  mocha:cli:mocha running Mocha in-process +2ms
  mocha:cli:cli entered main with raw args [] +0ms
  mocha:plugin-loader registered plugin def "mochaHooks" +0ms
  mocha:plugin-loader registered plugin def "mochaGlobalSetup" +0ms
  mocha:plugin-loader registered plugin def "mochaGlobalTeardown" +0ms
  mocha:plugin-loader registered 3 plugin defs (0 ignored) +0ms
  mocha:cli:run:helpers resolved required file tests/mocha.env to /home/patrick/Code/repo-mocha-issue/tests/mocha.env +0ms
  mocha:cli:run:helpers loaded required module "tests/mocha.env" +5ms
  mocha:cli:run:helpers loaded required module "ts-node/register" +175ms
  mocha:plugin-loader finalized plugins: [Object: null prototype] {} +195ms
  mocha:cli:run post-yargs config {
  package: [Getter/Setter],
  _: [],
  config: false,
  failZero: false,
  'fail-zero': false,
  parallel: false,
  require: [ 'tests/mocha.env', 'ts-node/register' ],
  extension: [ 'ts' ],
  bail: true,
  exit: true,
  recursive: true,
  jobs: 1,
  timeout: '2000',
  ignore: [ 'node_modules/**' ],
  diff: true,
  reporter: 'spec',
  slow: 75,
  ui: 'bdd',
  'watch-ignore': [ 'node_modules', '.git' ],
  watchIgnore: [ 'node_modules', '.git' ],
  spec: [ '**/*.test.ts' ],
  '$0': 'mocha'
} +0ms
  mocha:suite slow 75 +0ms
  mocha:suite timeout 2000 +0ms
  mocha:suite bail true +1ms
  mocha:mocha configured 0 global setup functions +0ms
  mocha:mocha configured 0 global teardown functions +0ms
  mocha:cli:run:helpers test files (in order):  [ '/home/patrick/Code/repo-mocha-issue/MathFunctions.test.ts' ] +0ms
  mocha:cli:run:helpers single run with 1 file(s) +1s
  mocha:mocha set lazy load to true +1s

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /home/patrick/Code/repo-mocha-issue/MathFunctions.test.ts
    at new NodeError (node:internal/errors:393:5)
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:79:11)
    at defaultGetFormat (node:internal/modules/esm/get_format:121:38)
    at defaultLoad (node:internal/modules/esm/load:81:20)
    at nextLoad (node:internal/modules/esm/loader:163:28)
    at ESMLoader.load (node:internal/modules/esm/loader:605:26)
    at ESMLoader.moduleProvider (node:internal/modules/esm/loader:457:22)
    at new ModuleJob (node:internal/modules/esm/module_job:63:26)
    at ESMLoader.#createModuleJob (node:internal/modules/esm/loader:480:17)
    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:434:34)
    at async Promise.all (index 0)
    at async ESMLoader.import (node:internal/modules/esm/loader:530:24)
    at async importModuleDynamicallyWrapper (node:internal/vm/module:438:15)
    at async formattedImport (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/nodejs/esm-utils.js:7:14)
    at async Object.exports.requireOrImport (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/nodejs/esm-utils.js:38:28)
    at async Object.exports.loadFilesAsync (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/nodejs/esm-utils.js:91:20)
    at async singleRun (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/cli/run-helpers.js:125:3)
    at async Object.exports.handler (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/cli/run.js:370:5)

[magicdawn]

use

NODE_OPTIONS="--loader ts-node/esm" mocha

mocha is using import() to load any test file. so the --require ts-node/register just do not work

see youself in
at async formattedImport (/home/patrick/Code/repo-mocha-issue/node_modules/mocha/lib/nodejs/esm-utils.js:7:14)

[patreeceeo]

Well, with that I get a different error at least.

TSError: ⨯ Unable to compile TypeScript:
MathFunctions.test.ts:9:6 - error TS2695: Left side of comma operator is unused and has no side effects.

9     (0, assert_1.default)(MathConstants_1.V_000);

Seems like something is wrong with the transpilation of Typescript in the test code now.

[juergba]

@patreeceeo I suggest studying this thread TypeStrong/ts-node#1007 which I suppose you haven't read, yet.
Furthermore you could transpile directly using tsc (without ts-node) in order to narrow down the cause.

Node's --experimental-loader (alias --loader) option is still in experimental status, so you will need to study and experiment.

This issue is related to ts-node. I will close this issue unless there is some interesting activity.