From 3bda7d852b6b3d2602f14ab2f61cdeab9298f7d2 Mon Sep 17 00:00:00 2001
From: Kristian Svalland <kristian.svalland@gmail.com>
Date: Tue, 3 Jan 2023 10:37:25 +0100
Subject: [PATCH] tree: Fix bug where loop index is not decremented.

Also add test to validate fix.

fixes https://github.com/gin-gonic/gin/issues/3459

Signed-off-by: Kristian Svalland <kristian.svalland@gmail.com>
---
 routes_test.go | 19 +++++++++++++++++++
 tree.go        |  6 +++---
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/routes_test.go b/routes_test.go
index cd8cf14145..ada8e1e457 100644
--- a/routes_test.go
+++ b/routes_test.go
@@ -670,3 +670,22 @@ func TestRouteContextHoldsFullPath(t *testing.T) {
 	w := PerformRequest(router, http.MethodGet, "/not-found")
 	assert.Equal(t, http.StatusNotFound, w.Code)
 }
+
+func TestEngineHandleMethodNotAllowedCornerCase(t *testing.T) {
+	r := New()
+	r.HandleMethodNotAllowed = true
+
+	base := r.Group("base")
+	base.GET("/metrics", handlerTest1)
+
+	v1 := base.Group("v1")
+
+	v1.GET("/:id/devices", handlerTest1)
+	v1.GET("/user/:id/groups", handlerTest1)
+
+	v1.GET("/orgs/:id", handlerTest1)
+	v1.DELETE("/orgs/:id", handlerTest1)
+
+	w := PerformRequest(r, "GET", "/base/v1/user/groups")
+	assert.Equal(t, http.StatusNotFound, w.Code)
+}
diff --git a/tree.go b/tree.go
index 3f34b8ee82..eccb3e6a16 100644
--- a/tree.go
+++ b/tree.go
@@ -459,7 +459,7 @@ walk: // Outer loop for walking the tree
 					// If the path at the end of the loop is not equal to '/' and the current node has no child nodes
 					// the current node needs to roll back to last valid skippedNode
 					if path != "/" {
-						for l := len(*skippedNodes); l > 0; {
+						for l := len(*skippedNodes); l > 0; l-- {
 							skippedNode := (*skippedNodes)[l-1]
 							*skippedNodes = (*skippedNodes)[:l-1]
 							if strings.HasSuffix(skippedNode.path, path) {
@@ -576,7 +576,7 @@ walk: // Outer loop for walking the tree
 			// If the current path does not equal '/' and the node does not have a registered handle and the most recently matched node has a child node
 			// the current node needs to roll back to last valid skippedNode
 			if n.handlers == nil && path != "/" {
-				for l := len(*skippedNodes); l > 0; {
+				for l := len(*skippedNodes); l > 0; l-- {
 					skippedNode := (*skippedNodes)[l-1]
 					*skippedNodes = (*skippedNodes)[:l-1]
 					if strings.HasSuffix(skippedNode.path, path) {
@@ -633,7 +633,7 @@ walk: // Outer loop for walking the tree
 
 		// roll back to last valid skippedNode
 		if !value.tsr && path != "/" {
-			for l := len(*skippedNodes); l > 0; {
+			for l := len(*skippedNodes); l > 0; l-- {
 				skippedNode := (*skippedNodes)[l-1]
 				*skippedNodes = (*skippedNodes)[:l-1]
 				if strings.HasSuffix(skippedNode.path, path) {