Typescript Functional Service Starter

Yet another (opinionated) typescript service starter template.

Opinions and limitations

1. Limits the non-pure code to infrastructure layer

Extends the ones from typescript-service-starter

1. Tries to follow Domain Driven Development and 3 Layers architecture
2. As little of externalities requirements as possible (outputs to stdout/stderr, no auth management, etc.)
3. No dependency on node_modules folder and filesystem at runtime, to allow bundling & small Docker image
4. Config should not default to either development or production (link)

And extends the ones from typescript-library-starter

1. Relies as much as possible on each included library's defaults
2. Only rely on GitHub Actions
3. Do not include documentation generation

Getting started

1. npx degit gjuchault/typescript-functional-service-starter my-project or click on Use this template button on GitHub!
2. cd my-project
3. npm install
4. git init (if you used degit)
5. npm run setup

To enable deployment, you will need to:

1. Setup NPM_TOKEN secret in GitHub actions (Settings > Secrets > Actions)
2. Give GITHUB_TOKEN write permissions for GitHub releases (Settings > Actions > General > Workflow permissions)

Features

Ecosystem

This template is based on Fastify with some nice defaults (circuit breaker, redis rate limit, etc.). It leverages PostgreSQL as a storage (through slonik), Redis as a cache through ioredis).

For the logging & telemetry part, it uses pino and OpenTelemetry (for both prometheus-like metrics & tracing). To handle distributed tracing, it expects W3C's traceparent header to carry trace id & parent span id.

This template also tries to be easy to deploy through esbuild's bundling. This means you can not leverage node_modules and file system at runtime: reading static files from node_modules, hooking require, etc. ill not be possible. This implies to be mindful on libraries (that would read static files from there older), or automatic instrumentation (that hook require). Yet it comes with super small Docker images hat are fast to deploy.

For the functional programming side, this project leverages fp-ts, as well as strict eslint rules from eslint-plugin-functional. While this is alright for the service's code, anything into infrastructure (and interaction with non functional libraries) will be less enforced. Anything that comes out is wrapped into functional.

Layers & folder structure

client             # generated fetch wrappers for your application
migrations         # database migrations (.sql files, no rollback)
src/
├── application    # service code
├── domain         # pure functions & typescript models of your entities
├── presentation   # communication layer (http)
├── repository     # storage of your entities
├── infrastructure # technical components (cache, database connection, etc.)
├── helpers        # utilities functions & non-domain code
└── test-helpers   # test utilities (starting default port, resetting database, etc.)

Client generation

This package can generate a type-safe client package when building (with npm run build:client). It can be used the following way:

import {
  createClient as createMyAppClient,
  createTraceHeader as createMyAppTraceHeader,
} from "my-app/client";

const myApp = createMyAppClient({
  baseUrl: "http://sometarget/",
  globalFetchOverrides: {
    headers: {
      "X-Custom-Token": "foo",
    },
  },
});

// GET /healthcheck
const data = await myApp.getHealthcheck({
  headers: {
    ...createMyAppTraceHeader({
      traceId: "some-trace-id",
      parentSpanId: "some-span-id",
    }),
  },
});

// POST /foo/bar?query=param { body: "json" }
const data2 = await myApp.postFooBar({ query: "param" }, { body: "json" });

The client will validate the server's response through zod.

Node.js, npm version

Typescript Service Starter relies on volta to ensure node version to be consistent across developers. It's also used in the GitHub workflow file.

Typescript

Leverages esbuild for blazing fast builds, but keeps tsc to generate .d.ts files. Generates two builds to support both ESM and CJS.

Commands:

• build: runs typechecking then generates CJS, ESM and d.ts files in the build/ directory
• clean: removes the build/ directory
• type:dts: only generates d.ts
• type:check: only run typechecking
• type:build: only generates CJS and ESM

Tests

typescript-functional-service-starter uses vitest. The coverage is done through vitest, using c8.

Commands:

• test: runs vitest test runner
• test:watch: runs vitest test runner in watch mode
• test:coverage: runs vitest test runner and generates coverage reports

Format & lint

This template relies on the combination of eslint — through typescript-eslint for linting and prettier for formatting. It also uses cspell to ensure spelling

Commands:

• format: runs prettier with automatic fixing
• format:check: runs prettier without automatic fixing (used in CI)
• lint: runs eslint with automatic fixing
• lint:check: runs eslint without automatic fixing (used in CI)
• spell:check: runs spellchecking

Releasing

Under the hood, this service uses semantic-release and commitizen. The goal is to avoid manual release process. Using semantic-release will automatically create a github release (hence tags) as well as an npm release. Based on your commit history, semantic-release will automatically create a patch, feature or breaking release.

Commands:

• cz: interactive CLI that helps you generate a proper git commit message, using commitizen
• semantic-release: triggers a release (used in CI)