Building Type-Safe APIs with OpenAPI and Code Generation

The Problem with Manual API Typing

When working with REST APIs in TypeScript, we often manually create types based on API documentation. This approach has several issues:

Enter Code Generation

By generating TypeScript types directly from OpenAPI specifications, we can:

Our Approach at Semfi

At Semfi, we built a custom NX plugin that:

// Generated code example
export const useGetUsers = (options?: UseQueryOptions) => {
  return useQuery({
    queryKey: ['users'],
    queryFn: () => api.getUsers(),
    ...options,
  });
};

Results

After implementing this approach:

Getting Started

Check out my open-source plugin openapi-ts-nx-plugin to get started with automatic code generation in your NX monorepo.