Add support for registering handlers for 404 routes

echo.go

@@ -183,6 +183,8 @@ const (
 	PROPFIND = "PROPFIND"
 	// REPORT Method can be used to get information about a resource, see rfc 3253
 	REPORT = "REPORT"
+	// RouteNotFound is special method type for routes handling "route not found" (404) cases
+	RouteNotFound = "echo_route_not_found"
 )
 
 // Headers
@@ -480,6 +482,16 @@ func (e *Echo) TRACE(path string, h HandlerFunc, m ...MiddlewareFunc) *Route {
 	return e.Add(http.MethodTrace, path, h, m...)
 }
 
+// RouteNotFound registers a special-case route which is executed when no other route is found (i.e. HTTP 404 cases)
+// for current request URL.
+// Path supports static and named/any parameters just like other http method is defined. Generally path is ended with
+// wildcard/match-any character (`/*`, `/download/*` etc).
+//
+// Example: `e.RouteNotFound("/*", func(c echo.Context) error { return c.NoContent(http.StatusNotFound) })`
+func (e *Echo) RouteNotFound(path string, h HandlerFunc, m ...MiddlewareFunc) *Route {
+	return e.Add(RouteNotFound, path, h, m...)
+}
+
 // Any registers a new route for all HTTP methods and path with matching handler
 // in the router with optional route-level middleware.
 func (e *Echo) Any(path string, handler HandlerFunc, middleware ...MiddlewareFunc) []*Route {
@@ -515,6 +527,7 @@ func (e *Echo) File(path, file string, m ...MiddlewareFunc) *Route {
 func (e *Echo) add(host, method, path string, handler HandlerFunc, middleware ...MiddlewareFunc) *Route {
 	name := handlerName(handler)
 	router := e.findRouter(host)
+	// FIXME: when handler+middleware are both nil ... make it behave like handler removal
 	router.Add(method, path, func(c Context) error {
 		h := applyMiddleware(handler, middleware...)
 		return h(c)

echo_test.go

@@ -766,6 +766,70 @@ func TestEchoNotFound(t *testing.T) {
 	assert.Equal(t, http.StatusNotFound, rec.Code)
 }
 
+func TestEcho_RouteNotFound(t *testing.T) {
+	var testCases = []struct {
+		name        string
+		whenURL     string
+		expectRoute interface{}
+		expectCode  int
+	}{
+		{
+			name:        "404, route to static not found handler /a/c/xx",
+			whenURL:     "/a/c/xx",
+			expectRoute: "GET /a/c/xx",
+			expectCode:  http.StatusNotFound,
+		},
+		{
+			name:        "404, route to path param not found handler /a/:file",
+			whenURL:     "/a/echo.exe",
+			expectRoute: "GET /a/:file",
+			expectCode:  http.StatusNotFound,
+		},
+		{
+			name:        "404, route to any not found handler /*",
+			whenURL:     "/b/echo.exe",
+			expectRoute: "GET /*",
+			expectCode:  http.StatusNotFound,
+		},
+		{
+			name:        "200, route /a/c/df to /a/c/df",
+			whenURL:     "/a/c/df",
+			expectRoute: "GET /a/c/df",
+			expectCode:  http.StatusOK,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			e := New()
+
+			okHandler := func(c Context) error {
+				return c.String(http.StatusOK, c.Request().Method+" "+c.Path())
+			}
+			notFoundHandler := func(c Context) error {
+				return c.String(http.StatusNotFound, c.Request().Method+" "+c.Path())
+			}
+
+			e.GET("/", okHandler)
+			e.GET("/a/c/df", okHandler)
+			e.GET("/a/b*", okHandler)
+			e.PUT("/*", okHandler)
+
+			e.RouteNotFound("/a/c/xx", notFoundHandler)  // static
+			e.RouteNotFound("/a/:file", notFoundHandler) // param
+			e.RouteNotFound("/*", notFoundHandler)       // any
+
+			req := httptest.NewRequest(http.MethodGet, tc.whenURL, nil)
+			rec := httptest.NewRecorder()
+
+			e.ServeHTTP(rec, req)
+
+			assert.Equal(t, tc.expectCode, rec.Code)
+			assert.Equal(t, tc.expectRoute, rec.Body.String())
+		})
+	}
+}
+
 func TestEchoMethodNotAllowed(t *testing.T) {
 	e := New()
 

group.go

@@ -107,6 +107,13 @@ func (g *Group) File(path, file string) {
 	g.file(path, file, g.GET)
 }
 
+// RouteNotFound implements `Echo#RouteNotFound()` for sub-routes within the Group.
+//
+// Example: `g.RouteNotFound("/*", func(c echo.Context) error { return c.NoContent(http.StatusNotFound) })`
+func (g *Group) RouteNotFound(path string, h HandlerFunc, m ...MiddlewareFunc) *Route {
+	return g.Add(RouteNotFound, path, h, m...)
+}
+
 // Add implements `Echo#Add()` for sub-routes within the Group.
 func (g *Group) Add(method, path string, handler HandlerFunc, middleware ...MiddlewareFunc) *Route {
 	// Combine into a new slice to avoid accidentally passing the same slice for

group_test.go

@@ -119,3 +119,68 @@ func TestGroupRouteMiddlewareWithMatchAny(t *testing.T) {
 	assert.Equal(t, "/*", m)
 
 }
+
+func TestGroup_RouteNotFound(t *testing.T) {
+	var testCases = []struct {
+		name        string
+		whenURL     string
+		expectRoute interface{}
+		expectCode  int
+	}{
+		{
+			name:        "404, route to static not found handler /group/a/c/xx",
+			whenURL:     "/group/a/c/xx",
+			expectRoute: "GET /group/a/c/xx",
+			expectCode:  http.StatusNotFound,
+		},
+		{
+			name:        "404, route to path param not found handler /group/a/:file",
+			whenURL:     "/group/a/echo.exe",
+			expectRoute: "GET /group/a/:file",
+			expectCode:  http.StatusNotFound,
+		},
+		{
+			name:        "404, route to any not found handler /group/*",
+			whenURL:     "/group/b/echo.exe",
+			expectRoute: "GET /group/*",
+			expectCode:  http.StatusNotFound,
+		},
+		{
+			name:        "200, route /group/a/c/df to /group/a/c/df",
+			whenURL:     "/group/a/c/df",
+			expectRoute: "GET /group/a/c/df",
+			expectCode:  http.StatusOK,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			e := New()
+			g := e.Group("/group")
+
+			okHandler := func(c Context) error {
+				return c.String(http.StatusOK, c.Request().Method+" "+c.Path())
+			}
+			notFoundHandler := func(c Context) error {
+				return c.String(http.StatusNotFound, c.Request().Method+" "+c.Path())
+			}
+
+			g.GET("/", okHandler)
+			g.GET("/a/c/df", okHandler)
+			g.GET("/a/b*", okHandler)
+			g.PUT("/*", okHandler)
+
+			g.RouteNotFound("/a/c/xx", notFoundHandler)  // static
+			g.RouteNotFound("/a/:file", notFoundHandler) // param
+			g.RouteNotFound("/*", notFoundHandler)       // any
+
+			req := httptest.NewRequest(http.MethodGet, tc.whenURL, nil)
+			rec := httptest.NewRecorder()
+
+			e.ServeHTTP(rec, req)
+
+			assert.Equal(t, tc.expectCode, rec.Code)
+			assert.Equal(t, tc.expectRoute, rec.Body.String())
+		})
+	}
+}

router.go

@@ -28,6 +28,9 @@ type (
 		isLeaf bool
 		// isHandler indicates that node has at least one handler registered to it
 		isHandler bool
+
+		// notFoundHandler is handler registered with RouteNotFound method and is executed for 404 cases
+		notFoundHandler HandlerFunc
 	}
 	kind          uint8
 	children      []*node
@@ -68,6 +71,7 @@ func (m *methodHandler) isHandler() bool {
 		m.put != nil ||
 		m.trace != nil ||
 		m.report != nil
+	// RouteNotFound/404 is not considered as a handler
 }
 
 func (m *methodHandler) updateAllowHeader() {
@@ -369,14 +373,12 @@ func (n *node) addHandler(method string, h HandlerFunc) {
 		n.methodHandler.trace = h
 	case REPORT:
 		n.methodHandler.report = h
+	case RouteNotFound:
+		n.notFoundHandler = h
 	}
 
 	n.methodHandler.updateAllowHeader()
-	if h != nil {
-		n.isHandler = true
-	} else {
-		n.isHandler = n.methodHandler.isHandler()
-	}
+	n.isHandler = n.methodHandler.isHandler()
 }
 
 func (n *node) findHandler(method string) HandlerFunc {
@@ -403,7 +405,7 @@ func (n *node) findHandler(method string) HandlerFunc {
 		return n.methodHandler.trace
 	case REPORT:
 		return n.methodHandler.report
-	default:
+	default: // RouteNotFound/404 is not considered as a handler
 		return nil
 	}
 }
@@ -506,7 +508,7 @@ func (r *Router) Find(method, path string, c Context) {
 			// No matching prefix, let's backtrack to the first possible alternative node of the decision path
 			nk, ok := backtrackToNextNodeKind(staticKind)
 			if !ok {
-				return // No other possibilities on the decision path
+				return // No other possibilities on the decision path, handler will be whatever context is reset to.
 			} else if nk == paramKind {
 				goto Param
 				// NOTE: this case (backtracking from static node to previous any node) can not happen by current any matching logic. Any node is end of search currently
@@ -522,15 +524,21 @@ func (r *Router) Find(method, path string, c Context) {
 		search = search[lcpLen:]
 		searchIndex = searchIndex + lcpLen
 
-		// Finish routing if no remaining search and we are on a node with handler and matching method type
-		if search == "" && currentNode.isHandler {
-			// check if current node has handler registered for http method we are looking for. we store currentNode as
-			// best matching in case we do no find no more routes matching this path+method
-			if previousBestMatchNode == nil {
-				previousBestMatchNode = currentNode
-			}
-			if h := currentNode.findHandler(method); h != nil {
-				matchedHandler = h
+		// Finish routing if is no request path remaining to search
+		if search == "" {
+			// in case of node that is handler we have exact method type match or something for 405 to use
+			if currentNode.isHandler {
+				// check if current node has handler registered for http method we are looking for. we store currentNode as
+				// best matching in case we do no find no more routes matching this path+method
+				if previousBestMatchNode == nil {
+					previousBestMatchNode = currentNode
+				}
+				if h := currentNode.findHandler(method); h != nil {
+					matchedHandler = h
+					break
+				}
+			} else if currentNode.notFoundHandler != nil {
+				matchedHandler = currentNode.notFoundHandler
 				break
 			}
 		}
@@ -550,7 +558,8 @@ func (r *Router) Find(method, path string, c Context) {
 			i := 0
 			l := len(search)
 			if currentNode.isLeaf {
-				// when param node does not have any children then param node should act similarly to any node - consider all remaining search as match
+				// when param node does not have any children (path param is last piece of route path) then param node should
+				// act similarly to any node - consider all remaining search as match
 				i = l
 			} else {
 				for ; i < l && search[i] != '/'; i++ {
@@ -575,13 +584,16 @@ func (r *Router) Find(method, path string, c Context) {
 			searchIndex += +len(search)
 			search = ""
 
-			// check if current node has handler registered for http method we are looking for. we store currentNode as
-			// best matching in case we do no find no more routes matching this path+method
+			if h := currentNode.findHandler(method); h != nil {
+				matchedHandler = h
+				break
+			}
+			// we store currentNode as best matching in case we do not find more routes matching this path+method. Needed for 405
 			if previousBestMatchNode == nil {
 				previousBestMatchNode = currentNode
 			}
-			if h := currentNode.findHandler(method); h != nil {
-				matchedHandler = h
+			if currentNode.notFoundHandler != nil {
+				matchedHandler = currentNode.notFoundHandler
 				break
 			}
 		}
@@ -604,6 +616,8 @@ func (r *Router) Find(method, path string, c Context) {
 		return // nothing matched at all
 	}
 
+	// matchedHandler could be method+path handler that we matched or notFoundHandler from node with matching path
+	// user provided not found (404) handler has priority over generic method not found (405) handler or global 404 handler
 	if matchedHandler != nil {
 		ctx.handler = matchedHandler
 	} else {
@@ -612,7 +626,9 @@ func (r *Router) Find(method, path string, c Context) {
 		currentNode = previousBestMatchNode
 
 		ctx.handler = NotFoundHandler
-		if currentNode.isHandler {
+		if currentNode.notFoundHandler != nil {
+			ctx.handler = currentNode.notFoundHandler
+		} else if currentNode.isHandler {
 			ctx.Set(ContextKeyHeaderAllow, currentNode.methodHandler.allowHeader)
 			ctx.handler = MethodNotAllowedHandler
 			if method == http.MethodOptions {