[paldepind]

Remove support for overriding the TypeScript compiler with SEMMLE_TYPESCRIPT_HOME. The JavaScript/TypeScript extractor now always uses its bundled TypeScript compiler.

Here's my rationale, copy/pasted from a Slack thread:

• The extractor is tightly coupled to the TypeScript dependency. Letting users override one of our internal dependencies is brittle.
• It's very hard to think of a reason why this is needed. We only use TypeScript for parsing, and parsing is backwards compatible.
• If we simply stop using SEMMLE_TYPESCRIPT_HOME then the 7.1 upgrade will be smoother for users. If anyone rely on it then the upgrade will go from breaking for their setup (requiring them to update to 7.1) into not breaking their setup (but ignoring an envvar they've set, if we don't want to do this silently we could log a warning).

[Copilot]

🔵 Needs a closer look

Removing the compiler override is an intentional compatibility break that needs maintainer sign-off.

No open issues 🎉

What changed in this PR

Removes SEMMLE_TYPESCRIPT_HOME support so the JavaScript/TypeScript extractor consistently uses its bundled TypeScript compiler.

Changes:

• Switches both compiler consumers to direct typescript imports.
• Deletes the override wrapper and its declaration file.
• Documents the compatibility break in a change note.

File	Description
javascript/​ql/​lib/​change-notes/​2026-10-22-remove-typescript-home.md	Documents removal of the compiler override.
javascript/​extractor/​lib/​typescript/​src/​typescript.js	Deletes the environment-dependent compiler wrapper.
javascript/​extractor/​lib/​typescript/​src/​typescript.d.ts	Deletes the wrapper’s type declaration.
javascript/​extractor/​lib/​typescript/​src/​main.ts	Imports TypeScript directly.
javascript/​extractor/​lib/​typescript/​src/​ast_extractor.ts	Imports TypeScript directly.

_{Review effort: Max}