Fix use-regex nginx annotation

Co-authored-by: Kevin Pollet <pollet.kevin@gmail.com>

pkg/provider/kubernetes/ingress-nginx/fixtures/ingresses/10-ingress-with-use-regex.yml

@@ -0,0 +1,22 @@
+---
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: ingress-with-use-regex
+  namespace: default
+  annotations:
+    nginx.ingress.kubernetes.io/use-regex: "true"
+
+spec:
+  ingressClassName: nginx
+  rules:
+    - host: use-regex.localhost
+      http:
+        paths:
+          - path: /test(.*)
+            pathType: ImplementationSpecific
+            backend:
+              service:
+                name: whoami
+                port:
+                  number: 80

pkg/provider/kubernetes/ingress-nginx/kubernetes.go

@@ -1060,7 +1060,7 @@ func buildRule(host string, pa netv1.HTTPIngressPath, config ingressConfig) stri
 			rules = append(rules, fmt.Sprintf("Path(`%s`)", pa.Path))
 		case netv1.PathTypePrefix:
 			if ptr.Deref(config.UseRegex, false) {
-				rules = append(rules, fmt.Sprintf("PathRegexp(`^%s`)", regexp.QuoteMeta(pa.Path)))
+				rules = append(rules, fmt.Sprintf("PathRegexp(`^%s`)", pa.Path))
 			} else {
 				rules = append(rules, buildPrefixRule(pa.Path))
 			}

pkg/provider/kubernetes/ingress-nginx/kubernetes_test.go

@@ -533,6 +533,51 @@ func TestLoadIngresses(t *testing.T) {
 				TLS: &dynamic.TLSConfiguration{},
 			},
 		},
+		{
+			desc: "Use Regex",
+			paths: []string{
+				"services.yml",
+				"ingressclasses.yml",
+				"ingresses/10-ingress-with-use-regex.yml",
+			},
+			expected: &dynamic.Configuration{
+				TCP: &dynamic.TCPConfiguration{
+					Routers:  map[string]*dynamic.TCPRouter{},
+					Services: map[string]*dynamic.TCPService{},
+				},
+				HTTP: &dynamic.HTTPConfiguration{
+					Routers: map[string]*dynamic.Router{
+						"default-ingress-with-use-regex-rule-0-path-0": {
+							Rule:       "Host(`use-regex.localhost`) && PathRegexp(`^/test(.*)`)",
+							RuleSyntax: "default",
+							Service:    "default-ingress-with-use-regex-whoami-80",
+						},
+					},
+					Middlewares: map[string]*dynamic.Middleware{},
+					Services: map[string]*dynamic.Service{
+						"default-ingress-with-use-regex-whoami-80": {
+							LoadBalancer: &dynamic.ServersLoadBalancer{
+								Servers: []dynamic.Server{
+									{
+										URL: "http://10.10.0.1:80",
+									},
+									{
+										URL: "http://10.10.0.2:80",
+									},
+								},
+								Strategy:       "wrr",
+								PassHostHeader: ptr.To(true),
+								ResponseForwarding: &dynamic.ResponseForwarding{
+									FlushInterval: dynamic.DefaultFlushInterval,
+								},
+							},
+						},
+					},
+					ServersTransports: map[string]*dynamic.ServersTransport{},
+				},
+				TLS: &dynamic.TLSConfiguration{},
+			},
+		},
 		{
 			desc:                           "Default Backend",
 			defaultBackendServiceName:      "whoami",