feat: Support .cts extension with ts-node 10+

[phated]

• I talked about the limitations in the ESM PR and suggestion in the ts-node transpile PR

---

Due to the way hardhat registers tasks, v3 can't support ESM (as I outlined at #1994 (comment)); however, TypeScript added ESM support and many projects are converting to ESM-only. The ts-node team added support for the .cts extension in TypeStrong/ts-node#1694, which allows individual files to be resolved as commonjs (see https://github.com/TypeStrong/ts-node#module-type-overrides).

This change should allow a monorepo to become "type": "module" and still use hardhat in commonjs mode. 🎉

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[github-actions]

Thanks for submitting this PR!

Unfortunately, it has some linter errors, so we can't merge it yet. Can you please fix them?

Running yarn lint:fix in the root of the repository may fix them automatically.

[fvictorio]

@alcuadrado this looks good to me. Do you want to take a look?

[fvictorio]

Hmm, this might need some changes to the Hardhat config loading logic.

[robwilkes]

edit: on further consideration I don't think this solves anything. we can rename all the files to .cts, which allows the project itself to be ESM compatible and we could load ESM modules into .ts files, but we wouldn't be able to load ESM modules into .cts files, which would basically be all the hardhat project files. whilst great it we can use hardhat inside a ESM project, it doesn't really allow the use of ESM modules, unless those are standalone scripts/modules not imported into any hardhat files.

this whole ESM thing is a mess.

---

I tried this and it doesn't seem to be detecting my .cts config file. and if I manually pass --config hardhat.config.cts I get mocha errors when running hardhat test. many modules are starting to move to ESM only, surely the best to way enable support for those is to have the hardhat project marked as ESM but hardhat support/load .cts files. surely this wouldn't take much to get over the line, it feels part way there already.

Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /Users/rob/src/test/node/hardhat-esm/test/Lock.ts
require() of ES modules is not supported.
require() of /Users/rob/src/test/node/hardhat-esm/test/Lock.ts from /Users/rob/src/test/node/hardhat-esm/node_modules/mocha/lib/mocha.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 /Users/rob/src/test/node/hardhat-esm/package.json.

    at createErrRequireEsm (/Users/rob/src/test/node/hardhat-esm/node_modules/ts-node/dist-raw/node-internal-errors.js:46:15)
    at assertScriptCanLoadAsCJSImpl (/Users/rob/src/test/node/hardhat-esm/node_modules/ts-node/dist-raw/node-internal-modules-cjs-loader.js:584:11)
    at Object.require.extensions.<computed> [as .ts] (/Users/rob/src/test/node/hardhat-esm/node_modules/ts-node/src/index.ts:1610:5)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at /Users/rob/src/test/node/hardhat-esm/node_modules/mocha/lib/mocha.js:414:36
    at Array.forEach (<anonymous>)
    at Mocha.loadFiles (/Users/rob/src/test/node/hardhat-esm/node_modules/mocha/lib/mocha.js:411:14) {
  code: 'ERR_REQUIRE_ESM'
}
Waiting for the debugger to disconnect...
error Command failed with exit code 1.

I tried editing this in package.json and renaming to Lock.cts but it doesn't seem to detect it and reports 0 passing.
"test": "mocha --recursive \"test/**/*.cts\"",

oh snap it worked.

hardhat-esm yarn hardhat --config hardhat.config.cts test
Debugger attached.
Debugger attached.
yarn run v1.22.15
$ /Users/rob/src/test/node/hardhat-esm/node_modules/.bin/hardhat --config hardhat.config.cts test
Debugger attached.


  Lock
    Deployment
      ✔ Should set the right unlockTime (687ms)
      ✔ Should set the right owner
      ✔ Should receive and store the funds to lock
      ✔ Should fail if the unlockTime is not in the future
    Withdrawals
      Validations
        ✔ Should revert with the right error if called too soon
        ✔ Should revert with the right error if called from another account
        ✔ Shouldn't fail if the unlockTime has arrived and the owner calls it
      Events
        ✔ Should emit an event on withdrawals
      Transfers
        ✔ Should transfer the funds to the owner


  9 passing (897ms)

it's hardcoded here

I'd love to contribute but I've only been working with node for about 2 weeks

[phated]

@robwilkes this is the very first, minor step into getting some semblance of interopt with type: module projects. Please hang tight until we can get things working together. As for this feature specifically, it requires ts-node 10+ and typescript 4.7+ otherwise it won't detect the extension correctly.

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[fvictorio]

Merging this to the esm feature branch, because I think these PRs will be easier to review and test together.