@codefast/typescript-config

Shared TypeScript configuration presets for projects that want one strict, bundler-first baseline and small, focused variants for libraries, React, and Next.js.

Strict by default — strict, noUncheckedIndexedAccess, noImplicitOverride, and verbatimModuleSyntax come from the base every preset extends.
Bundler-first — ESNext target and module with moduleResolution: "bundler", so exports/imports maps resolve the way Vite, esbuild, and friends resolve them.
Type-check only — the presets set noEmit; a separate build overlay turns emit and .d.ts generation on.
Plain JSON — no runtime code, nothing to import at runtime.

Installation

pnpm add -D @codefast/typescript-config

Requirements:

Node >= 24.
typescript >= 5 is a peer dependency (moduleResolution: "bundler" is a TypeScript 5 option).

Published on 0.x and versioned on its own track: breaking changes ship as minor versions, so pin the minor if you need stability.

Quick start

Extend the preset that matches your project in tsconfig.json. Keep the .json extension — the package exports only the full file names.

{
  "extends": "@codefast/typescript-config/base.json",
  "include": ["src"]
}

Options you set locally always win, so overriding a preset value is a one-line change:

{
  "extends": "@codefast/typescript-config/library.json",
  "compilerOptions": {
    "lib": ["DOM", "DOM.Iterable", "ESNext"]
  }
}

Presets

Preset	Extends	Purpose
`base.json`	—	Strict, bundler-first baseline: ESNext target and module, DOM + ESNext libs, type-check only.
`library.json`	`base.json`	Headless packages: `lib` is `ESNext` only, so relying on a browser global is a type error.
`react.json`	`base.json`	React with the automatic JSX runtime (`jsx: "react-jsx"`) — components need no `React` import.
`next.json`	`base.json`	Next.js apps: `jsx: "preserve"`, `incremental` builds, and the `next` TypeScript plugin.
`library-build.json`	(overlay)	Build-emit overrides for a build config: `noEmit: false`, `declaration` + `isolatedDeclarations`, declaration and source maps, `types: ["node"]`.

Choosing a preset

A publishable package with no browser coupling:

{
  "extends": "@codefast/typescript-config/library.json",
  "include": ["src"]
}

A React app or component library:

{
  "extends": "@codefast/typescript-config/react.json",
  "include": ["src"]
}

A Next.js app:

{
  "extends": "@codefast/typescript-config/next.json",
  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx"]
}

library-build.json is an overlay, not a standalone preset: it carries only the emit options, so layer it over your development config in a separate tsconfig.build.json. Listing both in extends keeps the strictness from library.json and adds .d.ts emit on top:

{
  "extends": ["./tsconfig.json", "@codefast/typescript-config/library-build.json"],
  "compilerOptions": {
    "rootDir": "./src",
    "outDir": "./dist"
  },
  "include": ["src/**/*.ts"],
  "exclude": ["src/**/*.test.ts"]
}

Then tsc -p tsconfig.build.json emits .js, .d.ts, and their maps into dist/. isolatedDeclarations requires an explicit type annotation on every export, which is what lets declarations be produced file by file.

Notable compiler options

All strictness comes from base.json, so every preset inherits it:

strict — the full strict family (strictNullChecks, noImplicitAny, and friends).
noUncheckedIndexedAccess — indexed access is typed T | undefined, forcing explicit handling.
noImplicitOverride — a method that overrides a base-class member must say override.
verbatimModuleSyntax — type-only imports must be written import type, so a transpiler can drop them without type information.
isolatedModules + moduleDetection: "force" — every file is a module and must transpile in isolation, as bundlers require.
module: "ESNext" + moduleResolution: "bundler" — modern ESM with bundler-style exports/imports resolution.
noEmit — presets type-check only; emitting is your bundler's job, or library-build.json's when tsc builds for you.
forceConsistentCasingInFileNames — catches import-path casing mismatches before they break case-sensitive CI.
skipLibCheck, esModuleInterop, resolveJsonModule — pragmatic defaults for consuming third-party packages and JSON.

Documentation

codefastlabs.com/docs/typescript-config — this document, rendered.
CHANGELOG.md — release notes for every published version.

Contributing

The package is developed in the codefast monorepo; the repo-wide contributing guide covers setup, the test taxonomy, and the release flow.

License

Released under the MIT License.