fastify-schema-to-typescript

How to install?

npm i -D fastify-schema-to-typescript

How to use?

Running npx fastify-schema-to-typescript will convert all schema.json files in src to schema.ts. You can then import schema.ts directly

import { RouteGeneric, schema } from "./schema";

const options = {
  schema: {
    params: schema.params,
    body: schema.body,
    response: schema.response,
  },
};

app.get<RouteGeneric>("/healthcheck", options, async () => {
  return { ok: true };
});

More options are available

npx fastify-schema-to-typescript -h

Usage: fastify-schema-to-typescript [options]

Options:
  -g, --glob <value>    glob matching JSON schema to convert (default: "src/**/schema.{json,yaml,yml}")
  -p, --prefix <value>  prefix to use before interfaces' name (default: "")
  -e, --ext <value>     file extension to use for generated files (default: ".ts")
  -m, --module <value>  module to import the RouteHandler type from (default: "fastify")
  -h, --help            display help for command

Project example

Here is a project structure that I'm usually using with that module. Each endpoint has a folder with a schema.yaml and index.ts

package.json
src/
  app.ts
  api/
    healthcheck/
      index.ts
      schema.yaml
    anotherEndpoint/
      index.ts
      schema.yaml
    ...

Running npx fastify-schema-to-typescript will convert schema.yaml to schema.ts that you can then import in your apps like that

app.ts

import fastify from "fastify";
import { healthcheck } from "./api";

export async function run() {
  const app = fastify();
  await app.register(healthcheck);

  await app.listen(3000);
}

run();

api/index.ts

export * from "./healthcheck";

api/healthcheck/schema.yaml

headers:
  type: object
  properties: ...

body:
  type: object
  properties: ...

query:
  type: object
  properties: ...

params:
  type: object
  properties: ...

api/healthcheck/index.ts

import { FastifyPluginAsync } from "fastify";
import { RouteGeneric, schema } from "./schema";

export const getHealthcheck: FastifyPluginAsync = async (app) => {
  app.get<RouteGeneric>("/healthcheck", { schema }, async () => {
    return { ok: true };
  });
};

I usually add the following in my package.json so I'm sure the code is in sync with the schemas

package.json

...
"scripts": {
  ...
  "build": "npm run clean && npm run generate && npm run compile",
  "compile": "tsc",
  "clean": "rimraf dist",
  "generate": "npx fastify-schema-to-typescript",
  ...
}

and I also update .gitignore to not include the generated schema.ts

.gitignore

...
schema.ts
...