Fix #271: Return 405 instead of 404 when request method doesn't match the route

mux.go

@@ -13,6 +13,10 @@ import (
 	"strings"
 )
 
+var (
+	ErrMethodMismatch = errors.New("method is not allowed")
+)
+
 // NewRouter returns a new router instance.
 func NewRouter() *Router {
 	return &Router{namedRoutes: make(map[string]*Route), KeepContext: false}
@@ -39,6 +43,10 @@ func NewRouter() *Router {
 type Router struct {
 	// Configurable Handler to be used when no route matches.
 	NotFoundHandler http.Handler
+
+	// Configurable Handler to be used when the request method does not match the route.
+	MethodNotAllowedHandler http.Handler
+
 	// Parent route, if this is a subrouter.
 	parent parentRoute
 	// Routes to be matched, in order.
@@ -65,6 +73,11 @@ func (r *Router) Match(req *http.Request, match *RouteMatch) bool {
 		}
 	}
 
+	if match.MatchErr == ErrMethodMismatch && r.MethodNotAllowedHandler != nil {
+		match.Handler = r.MethodNotAllowedHandler
+		return true
+	}
+
 	// Closest match for a router (includes sub-routers)
 	if r.NotFoundHandler != nil {
 		match.Handler = r.NotFoundHandler
@@ -105,9 +118,15 @@ func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		req = setVars(req, match.Vars)
 		req = setCurrentRoute(req, match.Route)
 	}
+
+	if handler == nil && match.MatchErr == ErrMethodMismatch {
+		handler = methodNotAllowedHandler()
+	}
+
 	if handler == nil {
 		handler = http.NotFoundHandler()
 	}
+
 	if !r.KeepContext {
 		defer contextClear(req)
 	}
@@ -344,6 +363,11 @@ type RouteMatch struct {
 	Route   *Route
 	Handler http.Handler
 	Vars    map[string]string
+
+	// MatchErr is set to appropriate matching error
+	// It is set to ErrMethodMismatch if there is a mismatch in
+	// the request method and route method
+	MatchErr error
 }
 
 type contextKey int
@@ -545,3 +569,12 @@ func matchMapWithRegex(toCheck map[string]*regexp.Regexp, toMatch map[string][]s
 	}
 	return true
 }
+
+// methodNotAllowed replies to the request with an HTTP status code 405.
+func methodNotAllowed(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusMethodNotAllowed)
+}
+
+// methodNotAllowedHandler returns a simple request handler
+// that replies to each request with a status code 405.
+func methodNotAllowedHandler() http.Handler { return http.HandlerFunc(methodNotAllowed) }