Elysia OpenAPI Code Generator

Generate fully-typed React Query hooks and TypeScript interfaces from OpenAPI specifications. Perfect for Elysia.js APIs and any OpenAPI 3.x compliant backend.

Features

- Type-Safe Hooks: Automatically generates React Query hooks with full TypeScript support
- OpenAPI 3.x Compatible: Works with any valid OpenAPI specification
- Multiple Input Sources: Fetch specs from URLs or local files
- Zero Configuration: Simple CLI with sensible defaults
- React Query Integration: Generates useQuery and useMutation hooks ready to use
- Flexible Arguments: Supports both flag-based and positional arguments

Installation

$3

``bash
bun add -d elysia-openapi-codegen
`

$3

`bash
npm install --save-dev elysia-openapi-codegen
`

$3

`bash
yarn add -D elysia-openapi-codegen
`

$3

`bash


Bun

`bash
elysia-codegen -i -o

`

Arguments:
- -i, --input - OpenAPI spec source (URL or file path)
- -o, --output

- Output directory for generated files
- -h, --help - Show help message

$3

#### Using Flag Arguments

`bash


From a URL

`bash


From a URL

`bash


Run directly with bun

The generator creates a single generated.ts file containing all types and hooks.

$3

All request/response types are automatically generated:

`typescript
import type { User, CreateUserBody, GetUsersResponse } from './generated';

// Use types in your components
const user: User = {
id: 1,
name: 'John Doe',
email: 'john@example.com'
};
`

$3

#### Query Hooks (GET requests)

`typescript
import { useGetUsers, useGetUserById } from './api/generated';

function UsersList() {
// Simple query with no parameters
const { data, isLoading, error } = useGetUsers();

if (isLoading) return

`typescript
import { useCreateUser, useUpdateUser, useDeleteUser } from './api/generated';
import { useQueryClient } from '@tanstack/react-query';

function CreateUserForm() {
const queryClient = useQueryClient();

const { mutate, isPending } = useCreateUser({
onSuccess: () => {
// Invalidate and refetch
queryClient.invalidateQueries({ queryKey: ['getUsers'] });
},
});

const handleSubmit = (e: React.FormEvent) => {
e.preventDefault();
const formData = new FormData(e.currentTarget);

mutate({
name: formData.get('name') as string,
email: formData.get('email') as string,
});
};

return (


`typescript
import { useGetUsers } from './api/generated';

function FilteredUsers({ status }: { status: string }) {
const { data } = useGetUsers(
{ status },
{
queryKey: ['users', status], // Custom query key
staleTime: 60000,
refetchOnWindowFocus: false,
}
);

return

`typescript
import { useCreateUser } from './api/generated';

function CreateUserForm() {
const { mutate, error, isError } = useCreateUser({
onError: (error) => {
console.error('Failed to create user:', error);
// Show toast notification, etc.
},
});

return (


`typescript
import { useUpdateUser } from './api/generated';
import { useQueryClient } from '@tanstack/react-query';

function UserEditor({ userId }: { userId: number }) {
const queryClient = useQueryClient();

const { mutate } = useUpdateUser({
onMutate: async (newUser) => {
// Cancel outgoing refetches
await queryClient.cancelQueries({ queryKey: ['getUserById', { id: userId }] });

// Snapshot the previous value
const previousUser = queryClient.getQueryData(['getUserById', { id: userId }]);

// Optimistically update
queryClient.setQueryData(['getUserById', { id: userId }], newUser);

return { previousUser };
},
onError: (err, newUser, context) => {
// Rollback on error
queryClient.setQueryData(
['getUserById', { id: userId }],
context?.previousUser
);
},
onSettled: () => {
queryClient.invalidateQueries({ queryKey: ['getUserById', { id: userId }] });
},
});

return

`
your-project/
├── src/
│ ├── api/
│ │ └── generated.ts # Generated by this tool
│ ├── components/
│ │ └── Users.tsx # Your components using the hooks
│ └── App.tsx
├── openapi.json # Your OpenAPI spec
└── package.json
`

Development

$3

`bash


Install dependencies

`bash


Run directly with Bun during development

`bash


Compile TypeScript to JavaScript

The build outputs JavaScript files to the dist/ folder, which is what gets published to npm.

How It Works

1. Fetches OpenAPI Spec: Reads from a URL or local file
2. Generates TypeScript Types: Creates interfaces from schema definitions
3. Creates React Query Hooks: Generates typed hooks for each endpoint
- GET requests → useQuery hooks
- POST/PUT/PATCH/DELETE → useMutation hooks
4. Outputs Single File: All types and hooks in one generated.ts file

Limitations

- Only supports application/json` content types
- Uses the first server URL as the base URL
- Assumes standard REST conventions for operations

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT

Related Projects

- Elysia - Fast and friendly Bun web framework
- TanStack Query - Powerful data synchronization for React
- OpenAPI - API specification standard