`@hono/zod-openapi`: App `basePath` is not used for OpenAPI route registration

[SimulatedGREG]

Summary

OpenAPIHono#openapi does not take into account a custom basePath. The path provided to openAPIRegistry.registerPath is incorrect when the app instance has a custom basePath defined.

Basic Reproduction

import { OpenAPIHono, createRoute } from '@hono/zod-openapi'
import { swaggerUI } from '@hono/swagger-ui'

// all routes are prefixed with "/foo"
const fooApp = new OpenAPIHono().basePath('/foo')

const route = createRoute({
  method: 'get',
  summary: 'foobar',
  path: '/bar',
  responses: {
    200: {
      description: 'OK'
    }
  }
})

fooApp.doc('/doc', {
  openapi: '3.0.0',
  info: {
    version: '0.0.0',
    title: 'localhost',
  },
})
fooApp.get('/swagger-ui', swaggerUI({ url: '/foo/doc' }))

// This produces the proper endpoint "GET /foo/bar"
// but Swagger UI shows route as "GET /bar"
fooApp.openapi(route, c => c.text('OK'))

// using CF Worker as test environment
export default fooApp

Swagger UI

http://localhost:8787/foo/swagger-ui

Testing "GET /foo/bar"

❯ http http://localhost:8787/foo/bar   
HTTP/1.1 200 OK
Content-Length: 2
Content-Type: text/plain;charset=UTF-8

OK

Proposed Solution

Use mergePath from hono/utils/url to ensure the path provided to registerPath includes the app _basePath.

https://github.com/honojs/middleware/blob/dde9854e51eeab6729050c48a400924dead975c9/packages/zod-openapi/src/index.ts#L268

this.openAPIRegistry.registerPath({
  ...route,
  path: mergePaths(this._basePath, route.path)
})

In local testing this works at one level of routing, but breaks when OpenAPIHono instances are nested. A separate fix would be needed to support Groups that change base or documentation would need to explain that nested app instances must be Grouped without changing base.

[mehdinourollah]

Any update here ? I couldn't use the proposed solution unfortunately...

[a4vg]

I'm using a workaround to make the requests from Swagger work, but it's definitely not a solution for the whole problem and it doesn't display the whole path for the endpoints.

export const app = new OpenAPIHono<{ Bindings: Bindings }>().basePath('/accounts/me');

app.doc('/doc', {
    ...
    servers: [
        {
            url: '/accounts/me'
        }
    ]
});

[leognmotta]

any updates here? this issue is still relevant since it does not generate correct openapi json file