From 9b85d4722a8760f2e2aec5e16ba4cc2ddc9898bc Mon Sep 17 00:00:00 2001
From: Derrick Hammer <derrick@derrickhammer.com>
Date: Sun, 12 Jan 2025 21:32:40 -0500
Subject: [PATCH] fix: https://github.com/gorilla/mux/pull/517

---
 mux_test.go | 157 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 route.go    |   9 ++-
 2 files changed, 163 insertions(+), 3 deletions(-)

diff --git a/mux_test.go b/mux_test.go
index bac758bc..1b01721a 100644
--- a/mux_test.go
+++ b/mux_test.go
@@ -3137,6 +3137,163 @@ func BenchmarkPopulateContext(b *testing.B) {
 	}
 }
 
+// testOptionsMiddleWare returns 200 on an OPTIONS request
+func testOptionsMiddleWare(inner http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == http.MethodOptions {
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+		inner.ServeHTTP(w, r)
+	})
+}
+
+// TestRouterOrder Should Pass whichever order route is defined
+func TestRouterOrder(t *testing.T) {
+	type requestCase struct {
+		request *http.Request
+		expCode int
+	}
+
+	tests := []struct {
+		name             string
+		routes           []*Route
+		customMiddleware MiddlewareFunc
+		requests         []requestCase
+	}{
+		{
+			name: "Routes added with same method and intersecting path regex",
+			routes: []*Route{
+				new(Route).Path("/a/b").Handler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					w.WriteHeader(http.StatusNotFound)
+				})).Methods(http.MethodGet),
+				new(Route).Path("/a/{a}").Handler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					w.WriteHeader(http.StatusOK)
+				})).Methods(http.MethodGet),
+			},
+			requests: []requestCase{
+				{
+					request: newRequest(http.MethodGet, "/a/b"),
+					expCode: http.StatusNotFound,
+				},
+				{
+					request: newRequest(http.MethodGet, "/a/a"),
+					expCode: http.StatusOK,
+				},
+			},
+		},
+		{
+			name: "Routes added with same method and intersecting path regex, path with pathVariable first",
+			routes: []*Route{
+				new(Route).Path("/a/{a}").Handler(http.HandlerFunc(
+					func(w http.ResponseWriter, r *http.Request) {
+						w.WriteHeader(http.StatusOK)
+					})).Methods(http.MethodGet),
+				new(Route).Path("/a/b").Handler(http.HandlerFunc(
+					func(w http.ResponseWriter, r *http.Request) {
+						w.WriteHeader(http.StatusNotFound)
+					})).Methods(http.MethodGet),
+			},
+			requests: []requestCase{
+				{
+					request: newRequest(http.MethodGet, "/a/b"),
+					expCode: http.StatusOK,
+				},
+				{
+					request: newRequest(http.MethodGet, "/a/a"),
+					expCode: http.StatusOK,
+				},
+			},
+		},
+		{
+			name: "Routes added same path - different methods, no path variables",
+			routes: []*Route{
+				new(Route).Path("/a/b").Handler(http.HandlerFunc(
+					func(w http.ResponseWriter, r *http.Request) {
+						w.WriteHeader(http.StatusOK)
+					})).Methods(http.MethodGet),
+				new(Route).Path("/a/b").Handler(http.HandlerFunc(
+					func(w http.ResponseWriter, r *http.Request) {
+						w.WriteHeader(http.StatusNotFound)
+					})).Methods(http.MethodOptions),
+			},
+			requests: []requestCase{
+				{
+					request: newRequest(http.MethodGet, "/a/b"),
+					expCode: http.StatusOK,
+				},
+				{
+					request: newRequest(http.MethodOptions, "/a/b"),
+					expCode: http.StatusNotFound,
+				},
+			},
+		},
+		{
+			name: "Routes added same path - different methods, with path variables and middleware",
+			routes: []*Route{
+				new(Route).Path("/a/{a}").Handler(http.HandlerFunc(
+					func(w http.ResponseWriter, r *http.Request) {
+						w.WriteHeader(http.StatusNotFound)
+					})).Methods(http.MethodGet),
+				new(Route).Path("/a/b").Handler(nil).Methods(http.MethodOptions),
+			},
+			customMiddleware: testOptionsMiddleWare,
+			requests: []requestCase{
+				{
+					request: newRequest(http.MethodGet, "/a/b"),
+					expCode: http.StatusNotFound,
+				},
+				{
+					request: newRequest(http.MethodOptions, "/a/b"),
+					expCode: http.StatusOK,
+				},
+			},
+		},
+		{
+			name: "Routes added same path - different methods, with path variables and middleware order reversed",
+			routes: []*Route{
+				new(Route).Path("/a/b").Handler(nil).Methods(http.MethodOptions),
+				new(Route).Path("/a/{a}").Handler(http.HandlerFunc(
+					func(w http.ResponseWriter, r *http.Request) {
+						w.WriteHeader(http.StatusNotFound)
+					})).Methods(http.MethodGet),
+			},
+			customMiddleware: testOptionsMiddleWare,
+			requests: []requestCase{
+				{
+					request: newRequest(http.MethodGet, "/a/b"),
+					expCode: http.StatusNotFound,
+				},
+				{
+					request: newRequest(http.MethodOptions, "/a/b"),
+					expCode: http.StatusOK,
+				},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			router := NewRouter()
+
+			if test.customMiddleware != nil {
+				router.Use(test.customMiddleware)
+			}
+
+			router.routes = test.routes
+			w := NewRecorder()
+
+			for _, requestCase := range test.requests {
+				router.ServeHTTP(w, requestCase.request)
+
+				if w.Code != requestCase.expCode {
+					t.Fatalf("Expected status code %d (got %d)", requestCase.expCode, w.Code)
+				}
+			}
+		})
+	}
+}
+
 // mapToPairs converts a string map to a slice of string pairs
 func mapToPairs(m map[string]string) []string {
 	var i int
diff --git a/route.go b/route.go
index 4eba5343..cee0a44c 100644
--- a/route.go
+++ b/route.go
@@ -103,11 +103,14 @@ func (r *Route) Match(req *http.Request, match *RouteMatch) bool {
 		return false
 	}
 
-	if match.MatchErr != nil && r.handler != nil {
+	// If a route matches, but the HTTP method does not, we do one of two (2) things:
+	// 1. Reset the match error if we find a matching method later.
+	// 2. Else, we override the matched handler in the event we have a possible fallback handler for that route.
+	//
+	// This prevents propagation of ErrMethodMismatch once a suitable match is found for a Method-Path combination
+	if match.MatchErr == ErrMethodMismatch {
 		// We found a route which matches request method, clear MatchErr
 		match.MatchErr = nil
-		// Then override the mis-matched handler
-		match.Handler = r.handler
 	}
 
 	// Yay, we have a match. Let's collect some info about it.