trailing-slash middleware should handle HEAD request

[sushichan044]

What version of Hono are you using?

4.7.5

What runtime/platform is your app running on? (with version if possible)

Cloudflare Workers

What steps can reproduce the bug?

1. run this hono app

    import { Hono } from "hono";
    import { trimTrailingSlash } from "hono/trailing-slash";
   
    const app = new Hono();
    app.use(trimTrailingSlash());
   
    app.get("/", (c) => {
      return c.text("Hello Hono!");
    });
   
    app.get("/foo", (c) => {
      return c.text("Hello Foo!");
    });
   
    export default app;

2. try GET / HEAD request with trailing slash

   ❯ curl -sSfL http://localhost:8787/foo/
   Hello Foo!%                                                                                                                                                                                                                                    
   ❯ curl -sSfL -I http://localhost:8787/foo/
   HTTP/1.1 404 Not Found
   Content-Type: text/plain; charset=UTF-8
   
   curl: (22) The requested URL returned error: 404 # UNEXPECTED!
   

See this repository for reproduction: https://github.com/sushichan044/hono-trailing-slash-head

What is the expected behavior?

The hono application should handle HEAD requests, same as GET requests

What do you see instead?

In the case of a HEAD request, the trailing-slash middleware is not invoked, so a 404 will be returned only for HEAD requests.

Additional information

In Hono, the GET handler implicitly handles HEAD requests as well.
ref: #1142

However, since the trailingSlash middleware only handles GET requests, the GET and HEAD methods behave differently when accessing the same endpoint.

[sushichan044]

prepared patch: #4049

[sushichan044]

Hello @yusukebe
Since the Hono implicitly routes HEAD requests to GET handlers, I think this fix will result in more consistent behavior.
I would like to know your opinion on this.

[yusukebe]

@sushichan044

Resolving this issue by PR #4049 is good! If you think this issue is a "bug," I think we can treat the PR as a fix and include the change in the patch version. Anyway, I'll review it later.

[sushichan044]

Yes, PR should be treated as fix, not feat. I will fix it. Thank you!