Have multiple notFound handlers

[kevinsimper]

What is the feature you are proposing?

Hi 😄

I am getting pretty far in my Hono server development and like it really! I tried to implement multiple notFound handlers and it seems like you can only have one handler. Tried to make a small example underneath.

import { Hono } from "hono";
import { serve } from "@hono/node-server";

const app = new Hono();

// API routes
const api = new Hono();
api.get("/users/:id", (c) => c.json({ id: c.req.param("id") }));

// Admin routes
const admin = new Hono();
admin.get("/dashboard", (c) => c.text("Admin Dashboard"));

// Mount sub-applications
app.route("/api", api);
app.route("/admin", admin);

// Problem: Only the last notFound handler is used globally
api.notFound((c) => {
  return c.json({ error: "API endpoint not found" }, 404);
});

admin.notFound((c) => {
  return c.html("<h1>Admin page not found</h1>", 404);
});

app.notFound((c) => {
  return c.text("Page not found", 404);
});

// Current behavior:
// GET /api/nonexistent -> "Page not found" (not the API-specific handler)
// GET /admin/nonexistent -> "Page not found" (not the admin-specific handler)
// GET /nonexistent -> "Page not found"

// Desired behavior:
// GET /api/nonexistent -> { "error": "API endpoint not found" }
// GET /admin/nonexistent -> <h1>Admin page not found</h1>
// GET /nonexistent -> "Page not found"

serve(app, (info) => {
  console.log(`Listening on http://localhost:${info.port}`); // Listening on http://localhost:3000
});

[EdamAme-x]

For now, it's necessary to use a fallback handler that corresponds to the "/*" path.