@typescript/old declares a tsc bin that wins over typescript@7 when the 6.0 compat package is installed

[knutwannheden]

🔎 Search Terms

@typescript/typescript6, @typescript/old, tsc bin, side-by-side, npm bin conflict

🕗 Version & Regression Information

• New with the 7.0 side-by-side story; typescript@7.0.2 alongside @typescript/typescript6@6.0.2.
• Related but distinct: Document that @typescript/typescript6 ships the API under @typescript/old (path-based tooling) #63866 asked for the @typescript/old layout to be documented for path-based tooling, and was closed as not planned. This is about the bin entries rather than the library path.

💻 Code

@typescript/typescript6 declares only the non-conflicting bin, which is correct:

$ node -p "JSON.stringify(require('@typescript/typescript6/package.json').bin)"
{"tsc6":"./bin/tsc6"}

Its dependency does not:

$ node -p "JSON.stringify(require('@typescript/typescript6/package.json').dependencies)"
{"@typescript/old":"npm:typescript@^6"}

$ node -p "JSON.stringify(require('@typescript/old/package.json').bin)"
{"tsc":"./bin/tsc","tsserver":"./bin/tsserver"}

So a project that runs TypeScript 7 as its compiler and keeps 6 available for a tool that still needs the old API:

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

ends up with the transitive package owning tsc:

$ readlink node_modules/.bin/tsc
../@typescript/old/bin/tsc

$ npx tsc --version
Version 6.0.3

🙁 Actual behavior

node_modules/.bin/tsc resolves to TypeScript 6. Any npm run build whose script is tsc --build ... silently compiles with 6 while the project's declared compiler is 7, and it succeeds, so nothing signals the substitution. I only noticed because a build that should have failed on unstable/* imports (TS1479 under module: node16) passed.

🙂 Expected behavior

Installing the compatibility package alongside TypeScript 7 leaves tsc pointing at TypeScript 7. @typescript/old is an implementation detail of the compatibility package and arguably should not contribute bin entries at all — publishing it without them, or under names that cannot collide, would do it.

Additional information about the issue

The documented side-by-side layout in the 7.0 announcement is the reverse of mine (typescript aliased to 6, @typescript/native for 7), and does not hit this, since tsc pointing at 6 is what that layout intends. The collision shows up in the inverse arrangement, which is the natural one for a project that has already moved to 7 and keeps 6 only for a library dependency.

Workaround is to name the compiler by path in the scripts:

"build": "node_modules/typescript/bin/tsc --build tsconfig.build.json"