🧪 @kaapi/validator-arktype

ArkType-powered validation plugin for Kaapi. Validate request params, payload, query, headers, and state using ArkType schemas. Includes built-in documentation helpers for seamless API docs generation.

⚠️ This library is ESM‑only. It requires an environment that supports ESM imports.

🚀 Installation

npm install @kaapi/validator-arktype

📦 Peer Dependency

Requires ArkType:

npm install arktype@^2.1.25

🛠️ Usage

🔌 Register the Plugin

import { Kaapi } from '@kaapi/kaapi';
import { validatorArk } from '@kaapi/validator-arktype';
import { type } from 'arktype';

const app = new Kaapi({
    port: 3000,
    host: 'localhost',
    docs: {
        disabled: false, // explicitly enables documentation generation
    },
});

await app.extend(validatorArk); // register the plugin

📐 Define a Schema

import { ValidatorArkSchema } from '@kaapi/validator-arktype';
import { type } from 'arktype';

const routeSchema: ValidatorArkSchema = {
    payload: type({
        name: 'string',
    }),
};

🧭 Create a Route

app.base()
    .ark(routeSchema)
    .route(
        {
            method: 'POST',
            path: '/items',
        },
        (req) => ({ id: Date.now(), name: req.payload.name })
    );

// or using inline handler
/*
app.base().ark(routeSchema).route({
  method: 'POST',
  path: '/items',
  handler: req => ({ id: Date.now(), name: req.payload.name })
})
*/

🧱 Build Routes Separately with withSchema

You can use withSchema to create validated routes without directly chaining from app.base(). This cleanly separates route construction from app registration.

import { withSchema } from '@kaapi/validator-arktype'
import { type } from 'arktype';

const schema = {
  payload: type({
      name: 'string'
  })
}

const route = withSchema(schema).route({
  method: 'POST',
  path: '/items',
  handler: req => ({ id: Date.now(), name: req.payload.name })
})

// later, during app setup
app.route(route)

This is the most flexible and convenient way to use @kaapi/validator-arktype when building modular APIs.

⚙️ Advanced Configuration

🚨 failAction

Control how validation failures are handled:

| Value | Behavior | Safe? | Description | | ---------- | ---------------------------- | ------------------------- | ------------------------------- | | 'error' | Reject with validation error | ✅ | Default safe behavior | | 'log' | Log and reject | ✅ | Useful for observability | | function | Custom handler | ✅ (developer-controlled) | Must return or throw explicitly | | 'ignore' | ❌ Not supported | ❌ | Unsafe and not implemented |

🧪 Example with Overrides

You can override ArkType validation behavior globally for all routes, or per route as needed.

🔁 Global Override (All Routes)

const app = new Kaapi({
    // ...
    routes: {
        plugins: {
            ark: {
                failAction: 'log',
            },
        },
    },
});

await app.extend(validatorArk);

This logs validation errors before throwing them for all ArkType-validated routes.

🔂 Per-Route Override

app.base()
    .ark({
        query: type({
            name: type(['string', '@', 'Optional name to personalize the greeting response'])
                .pipe((v) => v?.trim() ?? '')
                .to('0 < string <= 10')
                .default('World')
        }),
        failAction: async (request, h, err) => {
            if (Boom.isBoom(err)) {
                return h
                    .response({
                        ...err.output.payload,
                        details: err.data?.validationError?.issues,
                    })
                    .code(err.output.statusCode)
                    .takeover();
            }
            return err;
        },
    })
    .route({
        path: '/greetings',
        method: 'GET',
        handler: ({ query: { name } }) => `Hello ${name}!`,
    });

📤 File Upload Example

Multipart file uploads with ArkType validation is supported. Here's how to validate an uploaded image file and stream it back in the response:

app.base()
    .ark({
        payload: type({
            file: type({
                _data: type.instanceOf(Buffer),
                hapi: type({
                    filename: 'string',
                    headers: {
                        'content-type': '\'image/jpeg\' | \'image/jpg\' | \'image/png\'',
                    },
                }),
            }),
        }),
    })
    .route(
        {
            method: 'POST',
            path: '/upload-image',
            options: {
                description: 'Upload an image',
                payload: {
                    output: 'stream',
                    parse: true,
                    allow: 'multipart/form-data',
                    multipart: { output: 'stream' },
                    maxBytes: 1024 * 3_000,
                },
            },
        },
        (req, h) => h.response(req.payload.file._data).type(req.payload.file.hapi.headers['content-type'])
    );

🧾 Notes

• type({ ... }) is used to accommodate the structure of multipart file metadata.
• The _data: type.instanceOf(Buffer) field is automatically interpreted as a binary field by the documentation generator.
• This ensures correct OpenAPI and Postman documentation is generated, with the file field shown as a binary upload.
• The route streams the uploaded image back with its original content type.

🔄 Flexible API Design

Prefer Joi or migrating gradually? No problem.

You can still use app.route(...) with Joi-based validation while adopting ArkType via app.base().ark(...).route(...). This dual-mode support ensures graceful evolution, allowing traditional and modern routes to coexist without breaking changes.

📚 License

MIT

This package is tested as part of the Kaapi monorepo. See the main Kaapi README for coverage details.

🤝 Contributing

Contributions, issues, and feature requests are welcome! Feel free to open a discussion or submit a pull request.