Chapter 1 · Practice 6 of 6

Run the type checker in CI, separate from the build

Why it matters

Many fast tools, including Node's type stripping, esbuild, SWC and most bundlers, remove types without checking them. A project can build and run while full of type errors. The only thing that checks types is the TypeScript compiler (or its language service in your editor).

Add a dedicated step that runs tsc --noEmit (or tsc -b with project references) and fails the pipeline on any error. Run it on every pull request, next to tests and lint. With TypeScript 7 this step is usually short enough that there is no reason to skip it.

Add a typecheck script that runs tsc --noEmit and call it in CI
Fail the pipeline on type errors the same way you fail on test errors

Avoid

Assuming the bundler or node file.ts checked your types

Example

JSON

{
  "scripts": {
    "typecheck": "tsc --noEmit",
    "lint": "eslint .",
    "test": "vitest run"
  }
}