Document that `@typescript/typescript6` ships the API under `@typescript/old` (path-based tooling)

[Akshay090]

Context

The TypeScript 7.0 blog documents the recommended side-by-side install:

https://devblogs.microsoft.com/typescript/announcing-typescript-7-0/#running-side-by-side-with-typescript-6.0

{
  "devDependencies": {
    "@typescript/native": "npm:typescript@^7.0.2",
    "typescript": "npm:@typescript/typescript6@^6.0.2"
  }
}

Gap

With that layout, node_modules/typescript is effectively a thin compatibility package. The real TypeScript 6 API bundle lives under:

node_modules/@typescript/old/lib/typescript.js

(node_modules/typescript/lib/typescript.js is only a small re-export.)

That packaging detail isn’t called out in the side-by-side section. It matters for any tooling that matches paths under node_modules/typescript/ rather than resolving the package entrypoint.

Example we hit

We already had Jest configured to skip Babel-transforming TypeScript’s large CJS bundle:

transformIgnorePatterns: ['/node_modules/typescript/']

That was enough with a normal typescript@6 install. After switching to @typescript/typescript6, Jest still transformed @typescript/old/lib/typescript.js (~8MB), which hung CI suites that load @typescript-eslint/parser / RuleTester.

Fix on our side was:

transformIgnorePatterns: [
  '/node_modules/typescript/',
  '/node_modules/@typescript/',
]

Ask

Please add a short note to the side-by-side / @typescript/typescript6 blog guidance that:

1. The TS6 API implementation is provided via @typescript/old.
2. Path-based ignores/excludes aimed at node_modules/typescript/ may also need to cover node_modules/@typescript/ (Jest transformIgnorePatterns, bundler excludes, etc.).

Happy to send a docs PR if that’s preferred.

[RyanCavanaugh]

I don't really think we need to be documenting internal package layout -- this is supposed to be implementation details, so any tooling that's depending on it is going to have to adjust to observed changs.

[typescript-automation]

This issue has been marked as "Won't Fix" and has seen no recent activity. It has been automatically closed for house-keeping purposes.