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@cleverbrush/server-openapi

CI License: BSD-3-Clause

OpenAPI 3.1 specification generation for @cleverbrush/server. Converts endpoint registrations, schema definitions, and authentication configuration into a fully-formed OpenAPI document — no annotations, no decorators. Also generates AsyncAPI 3.0 documents for WebSocket subscription endpoints.

Features

  • generateOpenApiSpec() — converts @cleverbrush/server endpoint registrations into an OpenAPI 3.1 document.
  • generateAsyncApiSpec() — converts @cleverbrush/server WebSocket subscription registrations into an AsyncAPI 3.0 document.
  • serveAsyncApi() — middleware that lazily generates and caches the AsyncAPI spec; serves it at a configurable path (default: /asyncapi.json).
  • Schema conversion — maps @cleverbrush/schema builders to JSON Schema Draft 2020-12 via @cleverbrush/schema-json.
  • Path resolution — converts both colon-style paths (:id) and ParseStringSchemaBuilder templates to OpenAPI {param} format with per-parameter schemas.
  • Security mapping — translates @cleverbrush/auth authentication schemes to OpenAPI securitySchemes; maps per-endpoint authorize() to security arrays. Auto-detects OAuth 2.0 flows (authorizationCodeScheme, clientCredentialsScheme) and OpenID Connect (oidcScheme).
  • Top-level tags — pass tags: [{ name, description?, externalDocs? }] to OpenApiOptions; tag names are also auto-collected from endpoint registrations.
  • Request body examples — emit example / examples on Media Type Objects via .example() and .examples() on EndpointBuilder. Schema-level examples propagate automatically.
  • Binary / file responses — .producesFile(contentType?, description?) emits binary content types instead of JSON schemas for file download endpoints.
  • Multiple content types — .produces({ 'text/csv': {}, 'application/xml': { schema } }) emits a multi-entry content map for content-negotiated endpoints; an optional per-type schema override is supported.
  • Response headers — .responseHeaders(schema) documents response headers (X-Total-Count, rate-limit, cache-control, etc.) across every response code; each property becomes a named header entry with schema and description.
  • External docs — .externalDocs(url, description?) attaches an externalDocs object to the OpenAPI Operation Object.
  • Links — .links(defs) declares follow-up links from a response; emitted under the primary 2xx response's links map. Parameters can be raw runtime expression strings or a type-safe callback (response) => Record<string, unknown> where property accesses are resolved to $response.body#/<pointer> expressions automatically.
  • Callbacks — .callbacks(defs) declares async out-of-band callbacks on the Operation Object. The callback URL can be a raw expression string or a type-safe urlFrom callback resolved from the request body schema via property descriptors.
  • Webhooks — pass webhooks: [defineWebhook('name', options)] to OpenApiOptions (and register via ServerBuilder.webhook(def)) to emit a top-level webhooks map in the OpenAPI document.
  • serveOpenApi() — middleware that lazily generates and caches the spec; serves it at a configurable path (default: /openapi.json).
  • createOpenApiEndpoint() — returns a typed endpoint + handler pair for use with ServerBuilder.handle().
  • CLI / build script — writeOpenApiSpec() writes the spec to a file.

Installation

npm install @cleverbrush/server-openapi @cleverbrush/server @cleverbrush/schema

Quick Start

import { ServerBuilder, endpoint } from '@cleverbrush/server';
import { serveOpenApi } from '@cleverbrush/server-openapi';
import { object, string, number } from '@cleverbrush/schema';

const GetUser = endpoint
    .get('/api/users/:id')
    .summary('Get a user by ID')
    .tags('users');

const server = new ServerBuilder();

server
    .use(serveOpenApi({
        server,
        info: { title: 'My API', version: '1.0.0' }
    }))
    .handle(GetUser, ({ params }) => ({ id: params.id }));

await server.listen(3000);
// GET /openapi.json → OpenAPI 3.1 document

When server is provided, endpoint registrations, authentication config, and webhooks are derived automatically. You can still pass getRegistrations, authConfig, or webhooks explicitly to override any server-derived value.

Generating the Spec

As middleware (recommended)

import { serveOpenApi } from '@cleverbrush/server-openapi';

server.use(serveOpenApi({
    server,
    info: { title: 'My API', version: '1.0.0' },
    servers: [{ url: 'https://api.example.com', description: 'Production' }],
    path: '/openapi.json'   // default
}));

As a registered endpoint

import { createOpenApiEndpoint } from '@cleverbrush/server-openapi';

const { endpoint: openApiEp, handler } = createOpenApiEndpoint({
    server,
    info: { title: 'My API', version: '1.0.0' }
});

server.handle(openApiEp, handler);

Generating to a file (build scripts)

import { writeOpenApiSpec } from '@cleverbrush/server-openapi';

await writeOpenApiSpec({
    registrations: server.getRegistrations(),
    info: { title: 'My API', version: '1.0.0' },
    outputPath: './openapi.json'
});

$ref Deduplication (Named Schemas)

When the same schema definition is used by multiple endpoints, you can mark it with .schemaName() from @cleverbrush/schema so that generateOpenApiSpec() extracts it once into components/schemas and replaces every inline occurrence with a $ref pointer.

How it works

  1. Call .schemaName('ComponentName') on any @cleverbrush/schema builder you want to extract.
  2. Export the result as a constant and reuse the same reference wherever the schema is needed.
  3. generateOpenApiSpec() detects all named schemas via a pre-pass walk, emits them under components.schemas, and replaces inline definitions with $ref pointers.
import { object, string, number, array } from '@cleverbrush/schema';
import { endpoint } from '@cleverbrush/server';
import { generateOpenApiSpec } from '@cleverbrush/server-openapi';

// Mark once — reuse everywhere
const UserSchema = object({
    id:   number(),
    name: string(),
}).schemaName('User');

const GetUser   = endpoint.get('/api/users/:id').returns(UserSchema);
const ListUsers = endpoint.get('/api/users').returns(array(UserSchema));

const spec = generateOpenApiSpec({
    registrations: [GetUser.registration, ListUsers.registration],
    info: { title: 'My API', version: '1.0.0' }
});
// components.schemas.User → { type: 'object', properties: { id: …, name: … } }
// GET /api/users/:id  → responses.200.content['application/json'].schema: { $ref: '#/components/schemas/User' }
// GET /api/users      → responses.200.content['application/json'].schema: { type: 'array', items: { $ref: '…/User' } }

Nested named schemas inside request bodies are also resolved:

const AddressSchema = object({ street: string(), city: string() }).schemaName('Address');

// The wrapper is anonymous — inlined. The nested AddressSchema → $ref.
const CreateUserBody = object({ address: AddressSchema, name: string() });

Conflict rule

Registering two different schema instances under the same name throws immediately during spec generation:

const A = object({ x: string() }).schemaName('Thing');
const B = object({ y: number() }).schemaName('Thing'); // different instance!

generateOpenApiSpec({ registrations: [...], info: { … } });
// Error: Schema name "Thing" is already registered by a different schema instance.

Re-registering the same instance (because it appears in multiple endpoints) is a no-op.

SchemaRegistry (advanced)

SchemaRegistry and walkSchemas are also exported from @cleverbrush/server-openapi for custom tooling:

import { SchemaRegistry, walkSchemas } from '@cleverbrush/server-openapi';

const registry = new SchemaRegistry();
walkSchemas(MySchema, registry);

registry.getName(MySchema);    // 'MyComponentName' | null
registry.entries();            // IterableIterator<[name, SchemaBuilder]>
registry.isEmpty;              // boolean

Discriminated Unions

When a request body, response, or parameter schema is a discriminated union — all branches are objects sharing a required property with unique literal values — the generated spec automatically includes the OpenAPI discriminator keyword alongside anyOf.

If the union branches use .schemaName() and are extracted as $ref components, the discriminator also includes a mapping from each literal value to its $ref path:

const Cat = object({ type: string('cat'), name: string() }).schemaName('Cat');
const Dog = object({ type: string('dog'), breed: string() }).schemaName('Dog');
const PetBody = union(Cat).or(Dog);

const CreatePet = endpoint.post('/api/pets').body(PetBody);

// Generated spec:
// requestBody.content['application/json'].schema:
// {
//   anyOf: [{ $ref: '#/components/schemas/Cat' }, { $ref: '#/components/schemas/Dog' }],
//   discriminator: { propertyName: 'type', mapping: { cat: '#/components/schemas/Cat', dog: '#/components/schemas/Dog' } }
// }

Code generators like openapi-generator and orval use the discriminator to produce proper tagged union types.

Recursive Schemas

Self-referential schemas (tree nodes, nested menus, threaded comments) are supported via lazy() from @cleverbrush/schema. Call .schemaName() on the root schema and generateOpenApiSpec will:

  1. Register the named schema in components.schemas, expanding its definition exactly once.
  2. Replace every recursive reference inside the definition with the appropriate $ref pointer — breaking the cycle automatically.
import { object, number, array, lazy } from '@cleverbrush/schema';

type TreeNode = { value: number; children: TreeNode[] };

// TypeScript needs an explicit annotation for recursive types
const treeNode: ReturnType<typeof object> = object({
    value: number(),
    children: array(lazy(() => treeNode))
}).schemaName('TreeNode');

// Use treeNode as a body / response schema — no extra configuration needed
const CreateTree = endpoint.post('/api/tree').body(treeNode);

Generated spec (abbreviated):

components:
  schemas:
    TreeNode:
      type: object
      properties:
        value:  { type: integer }
        children:
          type: array
          items: { $ref: '#/components/schemas/TreeNode' }
paths:
  /api/tree:
    post:
      requestBody:
        content:
          application/json:
            schema: { $ref: '#/components/schemas/TreeNode' }

Request Body Examples

Pre-fill the Try it out panel in Swagger UI by attaching examples to endpoints.

Single example

const CreateUser = endpoint
    .post('/api/users')
    .body(UserSchema)
    .example({ name: 'Alice', email: 'alice@example.com' });

Emits example on the OpenAPI Media Type Object:

requestBody:
  content:
    application/json:
      schema: { ... }
      example: { name: Alice, email: alice@example.com }

Named examples

const CreateUser = endpoint
    .post('/api/users')
    .body(UserSchema)
    .examples({
        minimal: { summary: 'Minimal', value: { name: 'Alice' } },
        full: {
            summary: 'Complete',
            description: 'A fully populated user',
            value: { name: 'Alice', email: 'alice@example.com', age: 30 }
        }
    });

Schema-level examples

Examples attached directly to schemas via .example() propagate to parameter and response schemas in the generated spec:

const PageParam = number().example(1);
const UserResponse = object({ id: number(), name: string() }).example({ id: 1, name: 'Alice' });

Binary / File Responses

Use .producesFile() to declare that an endpoint returns a binary file instead of JSON. The generated spec emits the appropriate binary content type.

const ExportCsv = endpoint
    .get('/api/export')
    .producesFile('text/csv', 'CSV export');

const Download = endpoint
    .get('/api/download')
    .producesFile(); // defaults to application/octet-stream

Produces:

responses:
  '200':
    description: CSV export
    content:
      text/csv:
        schema: { type: string, format: binary }

When both .returns() and .producesFile() are set, the binary response takes precedence.

Authentication & Security Schemes

When you pass the server option, authentication configuration is picked up automatically from server.getAuthenticationConfig(). Security schemes and per-operation security arrays are generated without any extra configuration:

import { jwtScheme } from '@cleverbrush/auth';

const server = new ServerBuilder()
    .useAuthentication({
        defaultScheme: 'jwt',
        schemes: [jwtScheme({ secret: '...', mapClaims: c => c })]
    })
    .useAuthorization();

server.use(serveOpenApi({
    server,
    info: { title: 'My API', version: '1.0.0' }
}));

You can also pass authConfig explicitly (useful when not using the server option):

server.use(serveOpenApi({
    getRegistrations: () => server.getRegistrations(),
    info: { title: 'My API', version: '1.0.0' },
    authConfig: server.getAuthenticationConfig()
}));

JWT schemes generate { type: 'http', scheme: 'bearer', bearerFormat: 'JWT' }; cookie schemes generate { type: 'apiKey', in: 'cookie' }.

Top-Level Tags

OpenAPI supports a top-level tags array where each entry can carry a description and optional externalDocs. Pass a tags array to generateOpenApiSpec() (or any serving helper) to define them:

generateOpenApiSpec({
    registrations,
    info: { title: 'My API', version: '1.0.0' },
    tags: [
        {
            name: 'users',
            description: 'User management endpoints',
            externalDocs: { url: 'https://docs.example.com/users' }
        },
        { name: 'orders', description: 'Order management endpoints' }
    ]
});

When tags is omitted, unique tag names are automatically collected from all registered endpoints and emitted as name-only entries — so Swagger UI and Redoc still group operations correctly. Any endpoint tag not present in the explicit list is appended alphabetically.

OpenAPI Info

const info: OpenApiInfo = {
    title: 'My API',
    version: '2.0.0',
    description: 'Full description of my API.',
    termsOfService: 'https://example.com/tos',
    contact: { name: 'Support', email: 'support@example.com' },
    license: { name: 'MIT', url: 'https://opensource.org/licenses/MIT' }
};

Path Parameters

Both path styles are supported:

// Colon style — converted to {id}
endpoint.get('/api/users/:id');

// ParseStringSchemaBuilder — type-safe, with schema
import { route } from '@cleverbrush/server';
import { object, number } from '@cleverbrush/schema';

endpoint.get(route(object({ id: number().coerce() }), $t => $t`/api/users/${t => t.id}`));
// produces path "/api/users/{id}" with schema { type: 'number' }

AsyncAPI 3.0 (WebSocket Subscriptions)

generateAsyncApiSpec() and serveAsyncApi() convert @cleverbrush/server WebSocket subscription registrations into an AsyncAPI 3.0 document — no annotations required.

Middleware (recommended)

import { serveAsyncApi } from '@cleverbrush/server-openapi';

server.use(serveAsyncApi({
    server,
    info: { title: 'My API', version: '1.0.0' },
    // Optional: document the WebSocket servers
    servers: {
        production: { host: 'api.example.com', protocol: 'wss' },
        local: { host: 'localhost:3000', protocol: 'ws' },
    },
    path: '/asyncapi.json',  // default
}));
// GET /asyncapi.json → AsyncAPI 3.0 document (lazily generated, cached)

Programmatic use

import { generateAsyncApiSpec } from '@cleverbrush/server-openapi';

const spec = generateAsyncApiSpec({
    subscriptions: server.getSubscriptionRegistrations(),
    info: { title: 'My API', version: '1.0.0' },
    servers: {
        production: { host: 'api.example.com', protocol: 'wss' },
    },
});

// write to file, validate, upload to AsyncAPI Studio, etc.
await fs.writeFile('asyncapi.json', JSON.stringify(spec, null, 2));

Document structure

Each subscription endpoint becomes:

  • A channel (keyed by the subscription's operationId or a sanitised form of its path) with an address containing the WebSocket URL path.
  • A send operation if the endpoint has an outgoing schema (server → client events).
  • A receive operation if the endpoint has an incoming schema (client → server messages).

Named schemas (registered via .schemaName()) are collected into components.schemas and referenced via $ref pointers in the channel messages.

AsyncApiOptions

Field Type Default Description
subscriptions readonly SubscriptionRegistration[] — From server.getSubscriptionRegistrations()
info AsyncApiInfo — { title, version, description?, ... }
servers Record<string, AsyncApiServerEntry> {} Named WebSocket server entries
defaultHost string — Fallback host when servers is empty

License

BSD-3-Clause — see LICENSE.