feat: add --open to deno serve to open server in browser (#25340)

Change:
Supported --open flag with deno serve -> (deno serve --open
somescript.ts/js).
The action that takes place is openning the browser on the address that
the server is running on.

Signed-off-by: HasanAlrimawi <141642411+HasanAlrimawi@users.noreply.github.com>

cli/tools/serve.rs

@@ -1,5 +1,6 @@
 // Copyright 2018-2025 the Deno authors. MIT license.
 
+use std::str::FromStr;
 use std::sync::Arc;
 
 use deno_core::error::AnyError;
@@ -46,6 +47,12 @@ pub async fn serve(
 
   let worker_factory =
     Arc::new(factory.create_cli_main_worker_factory().await?);
+
+  if serve_flags.open_site {
+    let url = resolve_serve_url(serve_flags.host, serve_flags.port);
+    let _ = open::that_detached(url);
+  }
+
   let hmr = serve_flags
     .watch
     .map(|watch_flags| watch_flags.hmr)
@@ -180,3 +187,40 @@ async fn serve_with_watch(
   .await?;
   Ok(0)
 }
+
+fn resolve_serve_url(host: String, port: u16) -> String {
+  let host = if matches!(host.as_str(), "0.0.0.0" | "::") {
+    "127.0.0.1".to_string()
+  } else if std::net::Ipv6Addr::from_str(&host).is_ok() {
+    format!("[{}]", host)
+  } else {
+    host
+  };
+  if port == 80 {
+    format!("http://{host}/")
+  } else {
+    format!("http://{host}:{port}/")
+  }
+}
+
+#[cfg(test)]
+mod test {
+  use super::*;
+
+  #[test]
+  fn test_resolve_serve_url() {
+    assert_eq!(
+      resolve_serve_url("localhost".to_string(), 80),
+      "http://localhost/"
+    );
+    assert_eq!(
+      resolve_serve_url("0.0.0.0".to_string(), 80),
+      "http://127.0.0.1/"
+    );
+    assert_eq!(resolve_serve_url("::".to_string(), 80), "http://127.0.0.1/");
+    assert_eq!(
+      resolve_serve_url("::".to_string(), 90),
+      "http://127.0.0.1:90/"
+    );
+  }
+}