Support for Clean Running of .ts ESM Entry Points with ts-node/esm

[paullewallencom]

Environment Information

• Node.js version: 20.19.1
• ts-node version: ts-node@10.9.2
• TypeScript version: typescript@5.7.3
• OS: macOS

tsconfig.json settings:

{
"compilerOptions": {
"module": "NodeNext",
"moduleResolution": "NodeNext",
"target": "ES2022",
"esModuleInterop": true,
"allowSyntheticDefaultImports": true,
"strict": true,
"skipLibCheck": true
}
}

Summary of the Problem

When launching a TypeScript .ts ESM entry point directly using:

node --loader ts-node/esm run-mocha.ts

Node.js throws:

Error [ERR_REQUIRE_CYCLE_MODULE]: Cannot require() ES Module run-mocha.ts in a cycle

This happens even when all imports inside the .ts file are using await import() dynamically (no static imports), and the tsconfig.json uses "module": "NodeNext" and "moduleResolution": "NodeNext" correctly.

Steps to Reproduce

1. Clone this reproduction repository:
   👉 https://github.com/paullewallencom/issue-0000

2. Install dependencies:

npm install

3. Run the test script:

npm run test

4. Observe the cycle error crashing immediately.

What I Expected to Happen

• I expected ts-node/esm to properly defer static analysis or execution such that .ts ESM entrypoints could be executed cleanly without needing a .mjs bootstrap workaround.
• I expected dynamic await import('mocha') to avoid early cycle detection issues.

Actual Behavior

• Node detects a require cycle in the .ts entrypoint itself, even when using ts-node/esm.
• The only way to avoid the crash is to create a separate .mjs bootstrap file (e.g., run-mocha-bootstrap.mjs) and dynamically import the .ts file from there.

Notes

• I understand that Node's ESM loader is strict by design, but it seems like ts-node could provide a cleaner or more automated approach for .ts ESM entrypoints.
• I am happy to help contribute to documentation or potential enhancements if needed.
• Thank you very much for maintaining ts-node — it’s an incredibly valuable tool for TypeScript developers!