fix(zod-openapi): infer route middleware env in defineOpenAPIRoute handler

[VihaanAgarwal]

What & why

defineOpenAPIRoute (added in #1752) types its handler with only the app Env, so variables set by route-level middleware are dropped. Inside the handler c.var.* falls back to any:

const requireIdentity = createMiddleware<{
  Variables: { identity: { id: string } }
}>(async (c, next) => {
  c.set('identity', { id: '123' })
  await next()
})

const route = defineOpenAPIRoute({
  route: createRoute({
    method: 'get',
    path: '/me',
    middleware: [requireIdentity] as const,
    responses: { 200: { description: 'ok' } },
  }),
  handler: (c) => {
    c.var.identity // typed as `any`, should be `{ id: string }`
    return c.text('ok')
  },
})

OpenAPIHono.openapi() already covers this case: when a route has middleware it widens the handler env to RouteMiddlewareParams<R>['env'] & E. HandlerFromRoute, which defineOpenAPIRoute relies on, only passed E. This change applies the same widening in HandlerFromRoute, so a route built through defineOpenAPIRoute infers the middleware variables.

Thanks to @Aros for the report and for pointing at the existing openapi() handling.

Test

Added a type test in index.test-d.ts, mirroring the existing openapi() middleware-env test, that asserts the handler's c.var.foo / c.var.bar resolve to the route middleware variable types. It fails on main (Property 'foo' does not exist on type ...) and passes with the fix.

Fixes #1879

The author should do the following, if applicable

• Add tests
• Run tests
• yarn changeset at the top of this repo and push the changeset
• Follow the contribution guide

[changeset-bot]

🦋 Changeset detected

Latest commit: a14bd27

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@hono/zod-openapi	Patch

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.05%. Comparing base (a401fee) to head (a14bd27).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1986   +/-   ##
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  Coverage   92.05%   92.05%           
=======================================
  Files         115      115           
  Lines        4065     4065           
  Branches     1059     1059           
=======================================
  Hits         3742     3742           
  Misses        287      287           
  Partials       36       36           

Flag	Coverage Δ
zod-openapi	94.90% <ø> (ø)

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