fix(ext/http): do not set localhost to hostname unnecessarily (#24777)

This commit changes when to cause the hostname substition of `0.0.0.0` ->
`localhost`.

Currently we substitute `localhost` to the hostname on windows before
calling `options.onListen`, which prevents the users to do more advanced
thing using hostname string like
https://github.com/denoland/std/issues/5558. This PR changes it not to
substitute it when the user provide `onListen` callback.

closes #24776
unblocks https://github.com/denoland/std/issues/5558

2 files changed, 17 insertions, 0 deletions

diff --git a/tests/unit/serve_test.ts b/tests/unit/serve_test.ts
index fde6c7bee..19a8ccad1 100644
--- a/tests/unit/serve_test.ts
+++ b/tests/unit/serve_test.ts
@@ -4191,3 +4191,19 @@ Deno.test({
     'Operation `"op_net_listen_unix"` not supported on non-unix platforms.',
   );
 });
+
+Deno.test({
+  name: "onListen callback gets 0.0.0.0 hostname as is",
+}, async () => {
+  const { promise, resolve } = Promise.withResolvers<{ hostname: string }>();
+
+  const server = Deno.serve({
+    handler: (_) => new Response("ok"),
+    hostname: "0.0.0.0",
+    port: 0,
+    onListen: resolve,
+  });
+  const { hostname } = await promise;
+  assertEquals(hostname, "0.0.0.0");
+  await server.shutdown();
+});
diff --git a/tests/unit_node/net_test.ts b/tests/unit_node/net_test.ts
index f49ff0ef0..708d06386 100644
--- a/tests/unit_node/net_test.ts
+++ b/tests/unit_node/net_test.ts
@@ -79,6 +79,7 @@ Deno.test("[node/net] net.connect().unref() works", async () => {
     port: 0, // any available port will do
     handler: () => new Response("hello"),
     onListen: async ({ port, hostname }) => {
+      hostname = Deno.build.os === "windows" ? "localhost" : hostname;
       const { stdout, stderr } = await new Deno.Command(Deno.execPath(), {
         args: [
           "eval",