From 773767def0e0f29584a69bd760430167b7479d7d Mon Sep 17 00:00:00 2001
From: Jes Cok <xigua67damn@gmail.com>
Date: Wed, 26 Jun 2024 01:35:13 +0800
Subject: [PATCH] net/http: avoid appending an existing trailing slash to path
 again

This CL is similar to CL 562557, and it takes over CL 594175.

While here, unrelatedly remove mapKeys function, use slices.Sorted(maps.Keys(ms))
to simplify code.

Fixes #67657

Change-Id: Id8b99216f87a6dcfd6d5fa61407b515324c79112
Reviewed-on: https://go-review.googlesource.com/c/go/+/594737
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Joedian Reid <joedian@google.com>
---
 src/net/http/routing_tree_test.go |  5 ++---
 src/net/http/serve_test.go        | 16 ++++++++++++++++
 src/net/http/server.go            | 16 ++++------------
 3 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/src/net/http/routing_tree_test.go b/src/net/http/routing_tree_test.go
index 7de6b19507..f3f216357d 100644
--- a/src/net/http/routing_tree_test.go
+++ b/src/net/http/routing_tree_test.go
@@ -7,6 +7,7 @@ package http
 import (
 	"fmt"
 	"io"
+	"maps"
 	"strings"
 	"testing"
 
@@ -261,9 +262,7 @@ func TestMatchingMethods(t *testing.T) {
 		t.Run(test.name, func(t *testing.T) {
 			ms := map[string]bool{}
 			test.tree.matchingMethods(test.host, test.path, ms)
-			keys := mapKeys(ms)
-			slices.Sort(keys)
-			got := strings.Join(keys, ",")
+			got := strings.Join(slices.Sorted(maps.Keys(ms)), ",")
 			if got != test.want {
 				t.Errorf("got %s, want %s", got, test.want)
 			}
diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index 3ec10c2f14..b2858ba8f2 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -613,6 +613,22 @@ func TestMuxNoSlashRedirectWithTrailingSlash(t *testing.T) {
 	}
 }
 
+// Test that we don't attempt trailing-slash response 405 on a path that already has
+// a trailing slash.
+// See issue #67657.
+func TestMuxNoSlash405WithTrailingSlash(t *testing.T) {
+	mux := NewServeMux()
+	mux.HandleFunc("GET /{x}/", func(w ResponseWriter, r *Request) {
+		fmt.Fprintln(w, "ok")
+	})
+	w := httptest.NewRecorder()
+	req, _ := NewRequest("GET", "/", nil)
+	mux.ServeHTTP(w, req)
+	if g, w := w.Code, 404; g != w {
+		t.Errorf("got %d, want %d", g, w)
+	}
+}
+
 func TestShouldRedirectConcurrency(t *testing.T) { run(t, testShouldRedirectConcurrency) }
 func testShouldRedirectConcurrency(t *testing.T, mode testMode) {
 	mux := NewServeMux()
diff --git a/src/net/http/server.go b/src/net/http/server.go
index a5e98f1d95..1ff72a0455 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -16,6 +16,7 @@ import (
 	"internal/godebug"
 	"io"
 	"log"
+	"maps"
 	"math/rand"
 	"net"
 	"net/textproto"
@@ -2721,19 +2722,10 @@ func (mux *ServeMux) matchingMethods(host, path string) []string {
 	ms := map[string]bool{}
 	mux.tree.matchingMethods(host, path, ms)
 	// matchOrRedirect will try appending a trailing slash if there is no match.
-	mux.tree.matchingMethods(host, path+"/", ms)
-	methods := mapKeys(ms)
-	slices.Sort(methods)
-	return methods
-}
-
-// TODO(jba): replace with maps.Keys when it is defined.
-func mapKeys[K comparable, V any](m map[K]V) []K {
-	var ks []K
-	for k := range m {
-		ks = append(ks, k)
+	if !strings.HasSuffix(path, "/") {
+		mux.tree.matchingMethods(host, path+"/", ms)
 	}
-	return ks
+	return slices.Sorted(maps.Keys(ms))
 }
 
 // ServeHTTP dispatches the request to the handler whose
-- 
2.48.1