OpenAPI Typescript Client Generator

A powerful, highly customizable TypeScript client generator for OpenAPI specifications. Build type-safe API clients for any environment with unprecedented control over generated code.

Features

• Fully-typed: Generates TypeScript models for all schemas and operations
• Environment-agnostic: Generated clients work everywhere - browsers, Node.js, Sandbox environments, and more
• Validation support: Optional runtime validation for requests and responses
• Highly customizable: Control everything from naming conventions to file structure
• Production-ready: Used to build enterprise-grade API clients for Atlassian products
• Flexible schema loading: Load schemas from YAML or JSON, locally or remotely
• Modern specification support: Full support for OpenAPI 3.0 and 3.1
• Zero runtime dependencies: Generated code has no external dependencies unless explicitly configured

Real-world Examples

Built by the team behind production API clients:

• @resolution/jira-api-client - Fully-typed Jira API client
• @resolution/confluence-api-client - Fully-typed Confluence API client

These clients support multiple environments (Atlassian Connect Server/Client, Atlassian Forge Backend/Frontend) from a single codebase - showcasing the flexibility of this generator.

Comparison with Alternatives

| Feature | api-typescript-generator | openapi-typescript | openapi-ts + openapi-fetch | |-----------------------------|--------------------------|--------------------|--------------------------------------------| | Type Generation | ✅ | ✅ | ✅ | | Client Generation | ✅ | ✅ | ❌ (openapi-fetch can use generated types) | | Customizable File Structure | ✅ | ❌ | N/A | | Custom Naming Conventions | ✅ | ❌ | ❌ | | JSDoc Generation | ✅ | ✅ | ✅ | | JSDoc Customization | ✅ | ❌ | ❌ | | Validation | ✅ (configurable) | ❌ | ❌ | | Environment-agnostic | ✅ | ✅ | ✅ | | No runtime dependencies | ✅ | ❌ | ❌ |

Setup

Install using npm:

npm add --save-dev api-typescript-generator 

Or using yarn:

yarn add --dev api-typescript-generator

Configuration

Create a api-typescript-generator.config.ts file in your project root:

import path from 'path';
import {ApiTypescriptGeneratorConfig} from 'api-typescript-generator';

const configuration: ApiTypescriptGeneratorConfig = {
    generates: [
        {
            type: 'openapiClient',
            document: {
                // The source of the OpenAPI document.
                // Can also be { type: 'file', path: 'path/to/file.yaml' }
                // Both YAML and JSON formats are supported.
                source: {
                    type: 'url',
                    url: 'https://raw.githubusercontent.com/readmeio/oas-examples/main/3.1/yaml/petstore.yaml'
                }
            },
            // The output directory for the generated client.
            outputDirPath: path.join(__dirname, 'petstore-api-client'),
            client: {
                // The name of the generated client class.
                name: 'PetStoreApiClient',
                // Overrides the default base URL for the API.
                baseUrl: 'https://petstore.swagger.io/v2'
            }
        }
    ]
};

export default configuration;

Add a script to your package.json:

{
  "scripts": {
    "openapi-codegen": "api-typescript-generator generate api-typescript-generator.config.ts"
  }
}

Run the script:

npm run openapi-codegen

Basic Usage

import {PetStoreApiClient, PetStoreApiClientError} from './petstore-api-client';

const client = new PetStoreApiClient();

// Type-safe API calls
async function getPets() {
    const pets = await client.pet.findByStatus({status: 'available'});
    console.log(pets); // Fully typed response
}

// Error handling with typed errors
try {
    await client.pet.addPet({/* pet data */});
} catch (error) {
    if (error instanceof PetStoreApiClientError) {
        console.error('API Error:', error.response.status, error.message);
    }
}

Advanced Usage

Validation with Zod

Why you might want to enable validation:

• OpenAPI specifications can be incomplete or incorrect.
• Runtime validation can catch issues that static type checking cannot.
• Validation can help ensure that your API client behaves as expected.

// In config:
validation: {
    library: 'zod'
}

// Option 1. Throw validation errors
const client = new PetStoreApiClient();
const result = await client.pet.getPetById({petId: '123'});
// In case of validation error, an exception will be thrown.

// Option 2. Handle validation errors separately (i.e. send to Sentry)
const client = new PetStoreApiClient({
    handleValidationError(error) {
        Sentry.captureException(error);
    }
});
const result = await client.pet.getPetById({petId: '123'});
// In case of validation error, the error will be sent to Sentry, and the execution will continue.

Custom HTTP Client

const client = new PetStoreApiClient({
    fetch: customFetchImplementation,
    baseUrl: 'https://custom-petstore.example.com',
    middlewares: [
        request => {
            request.headers['X-Custom-Header'] = 'value';
            return request;
        }
    ]
});

Retry Logic

You can implement custom retry logic for your API client. This is useful for handling transient errors or rate limiting.

const client = new PetStoreApiClient({
    shouldRetryOnError: (error, attempt) => {
        if (error.status >= 500 && attempt < 3) {
            return new Promise((resolve) => {
                setTimeout(() => resolve(true), 100 * attempt);
            });
        }
        return false;
    }
});

Deprecated API Operations

In case if an operation is marked as deprecated in OpenAPI spec, the generator will add a @deprecated tag to the generated method. When calling a deprecated method, a warning will be logged to the console. You can customize the logging behavior by providing a custom logDeprecationWarning function in the client configuration.

const client = new PetStoreApiClient({
    logDeprecationWarning: ({
       operationName,
       path,
       method
    }) => {
        Sentry.captureMessage(`Deprecated API call: ${operationName} (${method.toUpperCase()} ${path})`);
    }
});

Customization Options

The generator offers unmatched customization:

1. File Structure Control

   • Custom directory structure
   • Configurable file naming patterns
   • Grouped or flat output

2. Naming Conventions

   • Model/interface naming patterns
   • Property naming transformation
   • Service method naming

3. Documentation

   • JSDoc generation with wordwrap control
   • Custom section ordering
   • Description formatting
   • Custom tags and annotations

4. Client Features

   • Response validation
   • Error handling strategies
   • Binary data processing
   • Custom fetch implementation
   • Custom request/response interceptors
   • Custom retry logic

Documentation

For full configuration options, see:

• OpenApiClientGeneratorConfig - Main configuration interface
• Models Configuration - Model generation options
• Services Configuration - Service generation options
• Validation Configuration - Validation options

Modules

Types are exported from three modules:

1. api-typescript-generator - Common API Generator types
2. api-typescript-generator/openapi-client - OpenAPI Client types
3. api-typescript-generator/openapi - OpenAPI Document types

Contributors

• Marat Dulin
• Mikhail Davydov

References

1. OpenAPI Specification
2. JSON Schema

License

This project is licensed under the MIT License. See the LICENSE file for details.