pattern aliases

README.md

@@ -32,6 +32,7 @@ The name mux stands for "HTTP request multiplexer". Like the standard `http.Serv
 * [Serving Single Page Applications](#serving-single-page-applications) (e.g. React, Vue, Ember.js, etc.)
 * [Registered URLs](#registered-urls)
 * [Walking Routes](#walking-routes)
+* [Re-using Regular Expressions](#re-using-regular-expressions)
 * [Graceful Shutdown](#graceful-shutdown)
 * [Middleware](#middleware)
 * [Handling CORS Requests](#handling-cors-requests)
@@ -439,6 +440,32 @@ func main() {
 }
 ```
 
+### Re-using Regular Expressions
+
+There can be a situation when you often need to specify some complex regular expressions inside your paths, e.g. uuid. This can be easily shorthanded:
+
+```go
+
+package main
+
+import (
+    "net/http"
+    "github.com/gorilla/mux"
+)
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	return
+}
+
+func main() {
+    r := mux.NewRouter().RegisterPattern("uuid", "[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-4[a-fA-F0-9]{3}-[8|9|aA|bB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}")
+    r.HandleFunc("/products/{id:uuid}", handler)
+    r.HandleFunc("/articles/{id:uuid}", handler)
+    r.HandleFunc("/authors/{id:uuid}", handler)
+}
+```
+
+
 ### Graceful Shutdown
 
 Go 1.8 introduced the ability to [gracefully shutdown](https://golang.org/doc/go1.8#http_shutdown) a `*http.Server`. Here's how to do that alongside `mux`:

example_router_test.go

@@ -0,0 +1,25 @@
+package mux_test
+
+import (
+	"fmt"
+	"github.com/gorilla/mux"
+	"net/http"
+)
+
+// This example demonstrates alias pattern registration on router
+func ExampleRouter_RegisterPattern() {
+
+	r := mux.NewRouter().RegisterPattern("uuid", "[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-4[a-fA-F0-9]{3}-[8|9|aA|bB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}")
+	route := r.Path("/category/{id:uuid}")
+
+	yes, _ := http.NewRequest("GET", "example.co/category/abe193ed-e0bc-4e1b-8e3c-736d5b381b60", nil)
+	no, _ := http.NewRequest("GET", "example.co/category/42", nil)
+
+	mathInfo := &mux.RouteMatch{}
+	fmt.Printf("Match: %v %q\n", route.Match(yes, mathInfo), yes.URL.Path)
+	fmt.Printf("Match: %v %q\n", route.Match(no, mathInfo), no.URL.Path)
+
+	// Output
+	// Match: true /category/abe193ed-e0bc-4e1b-8e3c-736d5b381b60
+	// Match: false /category/42
+}

mux.go

@@ -94,6 +94,8 @@ type routeConf struct {
 	buildScheme string
 
 	buildVarsFunc BuildVarsFunc
+
+	registeredPatterns map[string]string
 }
 
 // returns an effective deep copy of `routeConf`
@@ -124,6 +126,14 @@ func copyRouteRegexp(r *routeRegexp) *routeRegexp {
 	return &c
 }
 
+func (r *Router) RegisterPattern(alias string, pattern string) *Router {
+	if r.registeredPatterns == nil {
+		r.registeredPatterns = map[string]string{}
+	}
+	r.registeredPatterns[alias] = pattern
+	return r
+}
+
 // Match attempts to match the given request against the router's registered routes.
 //
 // If the request matches a route of this router or one of its subrouters the Route,

mux_test.go

@@ -216,6 +216,16 @@ func TestHost(t *testing.T) {
 			hostTemplate: `{v-1:[a-z]{3}}.{v-2:[a-z]{3}}.{v-3:[a-z]{3}}`,
 			shouldMatch:  true,
 		},
+		{
+			title:        "Host route with alias patterns",
+			route:        new(Route).RegisterPattern("version", "[a-z]{3}").Host("{v-1:version}.{v-2:version}.{v-3:version}"),
+			request:      newRequest("GET", "http://aaa.bbb.ccc/111/222/333"),
+			vars:         map[string]string{"v-1": "aaa", "v-2": "bbb", "v-3": "ccc"},
+			host:         "aaa.bbb.ccc",
+			path:         "",
+			hostTemplate: `{v-1:version}.{v-2:version}.{v-3:version}`,
+			shouldMatch:  true,
+		},
 	}
 	for _, test := range tests {
 		t.Run(test.title, func(t *testing.T) {
@@ -449,6 +459,36 @@ func TestPath(t *testing.T) {
 			pathTemplate: `/{category:a|b/c}/{product}/{id:[0-9]+}`,
 			shouldMatch:  true,
 		},
+		{
+			title:        "Path route with regexp alias patterns",
+			route:        new(Route).RegisterPattern("digits", "[0-9]+").Path("/{id:digits}"),
+			request:      newRequest("GET", "http://localhost/1"),
+			vars:         map[string]string{"id": "1"},
+			host:         "",
+			path:         "/1",
+			pathTemplate: `/{id:digits}`,
+			shouldMatch:  true,
+		},
+		{
+			title:        "Path route with regexp alias patterns",
+			route:        new(Route).RegisterPattern("uuid", "[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-4[a-fA-F0-9]{3}-[8|9|aA|bB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}").Path("/{category:uuid}/{product:uuid}"),
+			request:      newRequest("GET", "http://localhost/dce51145-5cc3-4b54-bfb0-7bdb64a67e4d/a385ddcb-278e-4234-93dd-4d7b0fcb95c1"),
+			vars:         map[string]string{"category": "dce51145-5cc3-4b54-bfb0-7bdb64a67e4d", "product": "a385ddcb-278e-4234-93dd-4d7b0fcb95c1"},
+			host:         "",
+			path:         "/dce51145-5cc3-4b54-bfb0-7bdb64a67e4d/a385ddcb-278e-4234-93dd-4d7b0fcb95c1",
+			pathTemplate: `/{category:uuid}/{product:uuid}`,
+			shouldMatch:  true,
+		},
+		{
+			title:        "Path route with regexp alias patterns passed through router",
+			route:        NewRouter().RegisterPattern("digits", "[0-9]+").Path("/{id:digits}"),
+			request:      newRequest("GET", "http://localhost/1"),
+			vars:         map[string]string{"id": "1"},
+			host:         "",
+			path:         "/1",
+			pathTemplate: `/{id:digits}`,
+			shouldMatch:  true,
+		},
 	}
 
 	for _, test := range tests {

regexp.go

@@ -15,8 +15,9 @@ import (
 )
 
 type routeRegexpOptions struct {
-	strictSlash    bool
-	useEncodedPath bool
+	strictSlash        bool
+	useEncodedPath     bool
+	registeredPatterns map[string]string
 }
 
 type regexpType int
@@ -85,6 +86,9 @@ func newRouteRegexp(tpl string, typ regexpType, options routeRegexpOptions) (*ro
 			return nil, fmt.Errorf("mux: missing name or pattern in %q",
 				tpl[idxs[i]:end])
 		}
+		if registeredPattern, ok := options.registeredPatterns[patt]; ok {
+			patt = registeredPattern
+		}
 		// Build the regexp pattern.
 		fmt.Fprintf(pattern, "%s(?P<%s>%s)", regexp.QuoteMeta(raw), varGroupName(i/2), patt)
 

route.go

@@ -31,6 +31,14 @@ type Route struct {
 	routeConf
 }
 
+func (r *Route) RegisterPattern(alias string, pattern string) *Route {
+	if r.registeredPatterns == nil {
+		r.registeredPatterns = map[string]string{}
+	}
+	r.registeredPatterns[alias] = pattern
+	return r
+}
+
 // SkipClean reports whether path cleaning is enabled for this route via
 // Router.SkipClean.
 func (r *Route) SkipClean() bool {
@@ -184,8 +192,9 @@ func (r *Route) addRegexpMatcher(tpl string, typ regexpType) error {
 		}
 	}
 	rr, err := newRouteRegexp(tpl, typ, routeRegexpOptions{
-		strictSlash:    r.strictSlash,
-		useEncodedPath: r.useEncodedPath,
+		strictSlash:        r.strictSlash,
+		useEncodedPath:     r.useEncodedPath,
+		registeredPatterns: r.registeredPatterns,
 	})
 	if err != nil {
 		return err