Type check with the TypeScript 7 native compiler

[pysnooLab]

Problem

TypeScript 7 (GA on 2026-07-08) is the Go compiler and is around 10x faster, but it cannot simply replace typescript@5.8: it no longer ships the JS API that typescript-eslint needs. Upstream closed the TypeScript 7 support request as not planned until that API lands in 7.1, so a plain bump breaks ESLint on every .ts/.tsx.

The codebase was not TS 7 ready either: baseUrl has been removed from the compiler options, and getList/getOne were redeclared non generic in the Supabase data provider while several call sites pass a type argument (getOne<Sale>). TS 5.8 accepted that, TS 7 rejects it with TS2558.

Solution

The side by side setup documented in the TypeScript 7.0 announcement:

• tsc comes from typescript@7 through the @typescript/native alias
• the typescript entry resolves to @typescript/typescript6, so ESLint keeps a supported peer
• typescript-eslint floor raised to ^8.58.0, the first release whose peer range widens to typescript <6.1.0. Below that, npm ci refuses the resolution outright.

The two binaries do not collide (tsc for 7, tsc6 for 6), so no script and no CI job changed. Removing the alias is all it takes once typescript-eslint supports 7.1.

Plus the compatibility fixes, all of which stay valid on TS 5.8:

• baseUrl dropped from both tsconfigs (paths now resolve relative to the tsconfig file, and tsconfig-paths 4.2 used by the Storybook docgen reports the same absoluteBaseUrl without it)
• getList/getOne made generic in the Supabase and FakeRest providers, which fixes the call sites at the root instead of stripping their type arguments
• scrollMargin added to the IntersectionObserver stub in the notes test, now required by the lib.dom shipped with TS 7

Measured here, 5 runs each: type checking drops from a 4.66s median to 1.10s (4.2x). The build is unchanged, vite build does not go through tsc.

Two known limits, both dormant:

• tsconfig.node.json (the vite.config.ts project) fails under TS 7 because the program pulls in node_modules/@swc/html/index.ts, a raw .ts shipped by a third party, incompatible with verbatimModuleSyntax. No script or CI job targets that project today.
• The editor needs the TypeScriptTeam.native-preview extension (VS Code >= 1.126) to get the native language server, it is not built into VS Code yet as of 1.131.

How to test

npm ci
npx tsc --version   # Version 7.0.2
npm run typecheck   # clean
npm run lint        # clean, ESLint still runs every rule
npm run test        # 405 passed on app + claude, 108 on functions

[erwanMarmelab]

tsconfig.node.json no longer compiles under TS 7, so vite.config.ts is untypecheckable.

[erwanMarmelab]

tsc type-checks nothing (files: []). We need to find another way (like npm run typecheck. But without the npm to let users use their own package manager)

[erwanMarmelab]

I still can find typescript6 in the package-lock