Propagate StrictSlash to subrouters instead of rudely turning it off

mux.go

@@ -119,9 +119,10 @@ func (r *Router) GetRoute(name string) *Route {
 // When false, if the route path is "/path", accessing "/path/" will not match
 // this route and vice versa.
 //
-// Special case: when a route sets a path prefix, strict slash is
-// automatically set to false for that route because the redirect behavior
-// can't be determined for prefixes.
+// Special case: when a route sets a path prefix using the PathPrefix() method,
+// strict slash is ignored for that route because the redirect behavior can't
+// be determined from a prefix alone. However, any subrouters created from that
+// route inherit the original StrictSlash setting.
 func (r *Router) StrictSlash(value bool) *Router {
 	r.strictSlash = value
 	return r

mux_test.go

@@ -660,6 +660,16 @@ func TestStrictSlash(t *testing.T) {
 			shouldMatch:    true,
 			shouldRedirect: false,
 		},
+		{
+			title:          "Propagate StrictSlash to subrouters",
+			route:          r.NewRoute().PathPrefix("/static/").Subrouter().Path("/images/"),
+			request:        newRequest("GET", "http://localhost/static/images"),
+			vars:           map[string]string{},
+			host:           "",
+			path:           "/static/images/",
+			shouldMatch:    true,
+			shouldRedirect: true,
+		},
 		{
 			title:          "Ignore StrictSlash for path prefix",
 			route:          r.NewRoute().PathPrefix("/static/"),

regexp.go

@@ -100,6 +100,7 @@ func newRouteRegexp(tpl string, matchHost, matchPrefix, strictSlash bool) (*rout
 	return &routeRegexp{
 		template:    template,
 		matchHost:   matchHost,
+		strictSlash: strictSlash,
 		regexp:      reg,
 		reverse:     reverse.String(),
 		varsN:       varsN,
@@ -114,6 +115,8 @@ type routeRegexp struct {
 	template string
 	// True for host match, false for path match.
 	matchHost bool
+	// The strictSlash value defined on the route, but disabled if PathPrefix was used.
+	strictSlash bool
 	// Expanded regexp.
 	regexp *regexp.Regexp
 	// Reverse template.
@@ -216,7 +219,7 @@ func (v *routeRegexpGroup) setMatch(req *http.Request, m *RouteMatch, r *Route)
 				m.Vars[v] = pathVars[k+1]
 			}
 			// Check if we should redirect.
-			if r.strictSlash {
+			if v.path.strictSlash {
 				p1 := strings.HasSuffix(req.URL.Path, "/")
 				p2 := strings.HasSuffix(v.path.template, "/")
 				if p1 != p2 {

route.go

@@ -294,7 +294,6 @@ func (r *Route) Path(tpl string) *Route {
 // Also note that the setting of Router.StrictSlash() has no effect on routes
 // with a PathPrefix matcher.
 func (r *Route) PathPrefix(tpl string) *Route {
-	r.strictSlash = false
 	r.err = r.addRegexpMatcher(tpl, false, true)
 	return r
 }