NormalizePath in actix-web-3 is not compatible with that in actix-web-2

[SuperHacker-liuan]

Expected Behavior

In actix-web-2.0.0, NormalizePath will convert the paths as following:

1. // => /
2. //v1// => /v1/
3. //v1//something => /v1/something

Current Behavior

When using TrailingSlash::Trim

1. // => /
2. //v1// => /v1
3. //v1//something => /v1/something

When using TrailingSlash::Always

1. // => /
2. //v1// => /v1/
3. //v1//something => /v1/something/

Possible Solution

Add an option called MergeOnly in TrailingSlash, which keeps the trailing slash's existance as it is.
This option should make NormalizePath compatible w/ actix-web-2.

Steps to Reproduce (for bugs)

#[actix_rt::test]
async fn keep_trailing_slash_unchange() {
    let mut app = init_service(
        App::new()
            .wrap(NormalizePath(TrailingSlash::MergeOnly))
            .service(web::resource("/").to(HttpResponse::Ok))
            .service(web::resource("/v1/something").to(HttpResponse::Ok))
            .service(web::resource("/v1/").to(HttpResponse::Ok)),
    )
    .await;

    let tests = vec![
        ("/", true), // root paths should still work
        ("/?query=test", true),
        ("///", true),
        ("/v1/something////", false),
        ("/v1/something/", false),
        ("//v1//something", true),
        ("/v1/", true),
        ("/v1", false),
        ("/v1////", true),
        ("//v1//", true),
        ("///v1", false),
    ];

    for (path, success) in tests {
        let req = TestRequest::with_uri(path).to_request();
        let res = call_service(&mut app, req).await;
        assert_eq!(res.status().is_success(), success);
    }
}

Context

I wanna migrate from actix-web-2.0 to 3.0, but failed to access some of my resource.

Your Environment

• Rust Version: rustc 1.46.0 (04488afe3 2020-08-24)
• Actix Web Version: 3.0.2