exercises-typescript

How to contribute

• Discuss the project on Telegram: https://t.me/hexletcommunity/12

Requirements

• docker
• docker compose V2
• make

Develop

# setup
make
# run
make compose
# check
make ci-check

# run tests
make compose-test

# run linters and validators
make code-lint
make compose-type-check
make compose-description-lint
make compose-schema-validate

Type checking

Type checking is a separate step from the tests, in two places:

• make type-check runs tsc --noEmit over the whole course. It is a prerequisite of make test, so make check and CI pick it up.
• bin/test2.sh type-checks a single lesson alongside its tests. This script — not make check — is what the platform runs against a student's solution, so a wrongly typed solution has to be rejected here.

Both are needed because vitest strips types with esbuild and never checks them: without a compiler step, expectTypeOf(...) assertions and @ts-expect-error directives in lesson tests silently pass no matter what the lesson exports.

Three settings in tsconfig.json are load-bearing for these steps, since nothing compiled the course before them:

• "moduleResolution": "bundler" — the old node10 value is a hard error in TypeScript 6, and bundler matches how vitest resolves the extensionless imports lessons use.
• "types": ["node"] — TypeScript 6 no longer picks up node_modules/@types on its own, and lessons use console and node:path. A lesson needing other ambient types has to add them here.
• "noEmit": true — so a bare tsc never drops .js files next to lessons.

This repository is created and maintained by the team and the community of Hexlet, an educational project. Read more about Hexlet.