From 1856953e530eab2cb8793c42c7e9c1e6b1dc2709 Mon Sep 17 00:00:00 2001
From: Bulat Gaifullin <gaifullinbf@gmail.com>
Date: Tue, 18 Apr 2017 09:50:17 +0300
Subject: [PATCH] Added method Route.GetPathRegexp

---
 mux_test.go | 21 +++++++++++++++++++++
 route.go    | 14 ++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/mux_test.go b/mux_test.go
index 1dec7ab..1ccc920 100644
--- a/mux_test.go
+++ b/mux_test.go
@@ -35,6 +35,7 @@ type routeTest struct {
 	path           string            // the expected path of the match
 	pathTemplate   string            // the expected path template to match
 	hostTemplate   string            // the expected host template to match
+	pathRegexp     string            // the expected path regexp
 	shouldMatch    bool              // whether the request is expected to match the route at all
 	shouldRedirect bool              // whether the request should result in a redirect
 }
@@ -270,6 +271,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/111",
 			pathTemplate: `/111/`,
+			pathRegexp:   `^/111/$`,
 			shouldMatch:  false,
 		},
 		{
@@ -290,6 +292,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/",
 			pathTemplate: `/`,
+			pathRegexp:   `^/$`,
 			shouldMatch:  true,
 		},
 		{
@@ -333,6 +336,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/111/222/333",
 			pathTemplate: `/111/{v1:[0-9]{3}}/333`,
+			pathRegexp:   `^/111/(?P<v0>[0-9]{3})/333$`,
 			shouldMatch:  false,
 		},
 		{
@@ -343,6 +347,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/111/222/333",
 			pathTemplate: `/{v1:[0-9]{3}}/{v2:[0-9]{3}}/{v3:[0-9]{3}}`,
+			pathRegexp:   `^/(?P<v0>[0-9]{3})/(?P<v1>[0-9]{3})/(?P<v2>[0-9]{3})$`,
 			shouldMatch:  true,
 		},
 		{
@@ -353,6 +358,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/111/222/333",
 			pathTemplate: `/{v1:[0-9]{3}}/{v2:[0-9]{3}}/{v3:[0-9]{3}}`,
+			pathRegexp:   `^/(?P<v0>[0-9]{3})/(?P<v1>[0-9]{3})/(?P<v2>[0-9]{3})$`,
 			shouldMatch:  false,
 		},
 		{
@@ -363,6 +369,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/a/product_name/1",
 			pathTemplate: `/{category:a|(?:b/c)}/{product}/{id:[0-9]+}`,
+			pathRegexp:   `^/(?P<v0>a|(?:b/c))/(?P<v1>[^/]+)/(?P<v2>[0-9]+)$`,
 			shouldMatch:  true,
 		},
 		{
@@ -373,6 +380,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/111/222/333",
 			pathTemplate: `/111/{v-1:[0-9]{3}}/333`,
+			pathRegexp:   `^/111/(?P<v0>[0-9]{3})/333$`,
 			shouldMatch:  true,
 		},
 		{
@@ -383,6 +391,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/111/222/333",
 			pathTemplate: `/{v-1:[0-9]{3}}/{v-2:[0-9]{3}}/{v-3:[0-9]{3}}`,
+			pathRegexp:   `^/(?P<v0>[0-9]{3})/(?P<v1>[0-9]{3})/(?P<v2>[0-9]{3})$`,
 			shouldMatch:  true,
 		},
 		{
@@ -393,6 +402,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/a/product_name/1",
 			pathTemplate: `/{product-category:a|(?:b/c)}/{product-name}/{product-id:[0-9]+}`,
+			pathRegexp:   `^/(?P<v0>a|(?:b/c))/(?P<v1>[^/]+)/(?P<v2>[0-9]+)$`,
 			shouldMatch:  true,
 		},
 		{
@@ -403,6 +413,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/daily-2016-01-01",
 			pathTemplate: `/{type:(?i:daily|mini|variety)}-{date:\d{4,4}-\d{2,2}-\d{2,2}}`,
+			pathRegexp:   `^/(?P<v0>(?i:daily|mini|variety))-(?P<v1>\d{4,4}-\d{2,2}-\d{2,2})$`,
 			shouldMatch:  true,
 		},
 		{
@@ -413,6 +424,7 @@ func TestPath(t *testing.T) {
 			host:         "",
 			path:         "/111/222",
 			pathTemplate: `/{v1:[0-9]*}{v2:[a-z]*}/{v3:[0-9]*}`,
+			pathRegexp:   `^/(?P<v0>[0-9]*)(?P<v1>[a-z]*)/(?P<v2>[0-9]*)$`,
 			shouldMatch:  true,
 		},
 	}
@@ -421,6 +433,7 @@ func TestPath(t *testing.T) {
 		testRoute(t, test)
 		testTemplate(t, test)
 		testUseEscapedRoute(t, test)
+		testRegexp(t, test)
 	}
 }
 
@@ -1499,6 +1512,14 @@ func testTemplate(t *testing.T, test routeTest) {
 	}
 }
 
+func testRegexp(t *testing.T, test routeTest) {
+	route := test.route
+	routePathRegexp, regexpErr := route.GetPathRegexp()
+	if test.pathRegexp != "" && regexpErr == nil && routePathRegexp != test.pathRegexp {
+		t.Errorf("(%v) GetPathRegexp not equal: expected %v, got %v", test.title, test.pathRegexp, routePathRegexp)
+	}
+}
+
 type TestA301ResponseWriter struct {
 	hh     http.Header
 	status int
diff --git a/route.go b/route.go
index 5544c1f..d3ba6cd 100644
--- a/route.go
+++ b/route.go
@@ -558,6 +558,20 @@ func (r *Route) GetPathTemplate() (string, error) {
 	return r.regexp.path.template, nil
 }
 
+// GetPathRegexp returns the expanded regular expression used to match route path.
+// This is useful for building simple REST API documentation and for instrumentation
+// against third-party services.
+// An error will be returned if the route does not define a path.
+func (r *Route) GetPathRegexp() (string, error) {
+	if r.err != nil {
+		return "", r.err
+	}
+	if r.regexp == nil || r.regexp.path == nil {
+		return "", errors.New("mux: route does not have a path")
+	}
+	return r.regexp.path.regexp.String(), nil
+}
+
 // GetHostTemplate returns the template used to build the
 // route match.
 // This is useful for building simple REST API documentation and for instrumentation