feat(client): Add `ApplyGlobalResponse` type helper for RPC Client

[mohankumarelec]

Problem

Hono RPC client doesn't infer response types from global error handlers like app.onError() or global middlewares like app.use("*"). This means developers lose type safety for common error responses like 500 and so on when using the RPC client.

Solution

Added ApplyGlobalResponse<App, ResponseType, StatusCode, Format> helper that merges global error response types into all routes.

Usage:

const app = new Hono()
  .get('/users', (c) => c.json({ users: [...] }))
  .onError((err, c) => c.json({ error: err.message }, 500))

// Apply global error type
type AppWithErrors = ApplyGlobalResponse<typeof app, { error: string }, 500, 'json'>

const client = hc<AppWithErrors>('http://api.example.com')
// Now client knows about both success and error responses

The author should do the following, if applicable

• [x] Add tests
• [x] Run tests
• [x] bun run format:fix && bun run lint:fix to format the code
• [x] Add TSDoc/JSDoc to document the code

[mohankumarelec]

Please let me know if the changes looks good, so that i can create a PR for the honojs/website as well so that the docs are updated. Thanks

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 91.49%. Comparing base (b06005a) to head (580db4b). :warning: Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4556   +/-   ##
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  Coverage   91.49%   91.49%           
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  Files         172      172           
  Lines       11230    11230           
  Branches     3257     3257           
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  Hits        10275    10275           
  Misses        954      954           
  Partials        1        1           

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[yusukebe]

@mohankumarelec Thank you for the PR!

Hey @NamesMT What do you think of this feature? I think this is an interesting idea. But I don't know if the API is best or not.