Example code from today's decorators presentation! Uses the older Stage 2 decorators API - look for the Stage 3 decorators API to release in Deno 1.40.

hono_decorators.ts

// deno-lint-ignore-file no-explicit-any
import { Hono } from "https://deno.land/x/hono@v3.12.0/mod.ts";
import { Context } from "https://deno.land/x/hono@v3.12.0/context.ts";
import * as dejs from "https://deno.land/x/dejs@0.10.3/mod.ts";

// Initialize class routes by instantiating a version of them
export function register(...args: any) {
  args.forEach((C: any) => {
    console.log("Mounting routes for", C.name);
    new C();
  });
}

// Create a single, module-scoped Hono application
export const app = new Hono();

export function route(path = "/", method = "get"): any {
  return function (proto: any, _methodName: any, context: any): any {
    // Register a route that calls the given method.
    app.all(path, async (c, next) => {
      if (c.req.method.toLowerCase() !== method.toLowerCase()) {
        return next();
      }

      // Call original function
      const originalValue = await context.value.call(proto, c);

      // Render JSON or HTML body
      if (typeof originalValue === "string") {
        return c.html(originalValue);
      } else {
        return c.json(originalValue);
      }
    });

    // Pass back wrapped function (unchanged)
    return {
      value: context.value,
    };
  };
}

export function template(templateName: string): any {
  return function (
    proto: any,
    _methodName: any,
    context: any,
  ): any {
    async function wrapped(c: Context): Promise<any> {
      const originalValue = await context.value.call(proto, c);
      return dejs.renderFileToString(templateName, {
        data: originalValue,
      });
    }

    // Pass back wrapped function
    return {
      value: wrapped,
    };
  };
}

list.ejs

<h1>Todos</h1>
<ul>
<% data.forEach(val => { %>
  <li><%= val.value.todo %></li>
<% }); %>
</ul>

main.ts

import { app, register } from "./hono_decorators.ts";
import { TodoResource } from "./todo.ts";

// Register route handlers through static initialization
register(TodoResource);

// Mount Hono app to serve incoming requests
Deno.serve(app.fetch);

todo.ts

import { Context } from "https://deno.land/x/hono@v3.12.0/context.ts";
import { route, template } from "./hono_decorators.ts";

// Create a persistent KV database
const kv = await Deno.openKv();

export class TodoResource {
  @route("/todos", "GET")
  @template("list.ejs")
  async listTodos() {
    const iter = await kv.list({ prefix: ["todos"] });
    const todos = [];
    for await (const res of iter) todos.push(res);
    return todos;
  }

  @route("/todos", "POST")
  async createTodo(c: Context) {
    const { todo, done } = await c.req.json();
    const id = crypto.randomUUID();
    return await kv.set(["todos", id], { id, todo, done });
  }

  @route("/todos/:id", "GET")
  async getTodo(c: Context) {
    const id = c.req.param("id");
    return await kv.get(["todos", id]);
  }

  @route("/todos/:id", "POST")
  async updateTodo(c: Context) {
    const id = c.req.param("id");
    const { todo, done } = await c.req.json();
    return await kv.set(["todos", id], { id, todo, done });
  }
}