Add edge case for root path with rewrite-target

provider/kubernetes/fixtures/ingressAnnotations_ingresses.yml

@@ -161,6 +161,23 @@ spec:
           servicePort: 80
         path: /api
 
+---
+  apiVersion: extensions/v1beta1
+  kind: Ingress
+  metadata:
+    annotations:
+      ingress.kubernetes.io/rewrite-target: /app
+    namespace: testing
+  spec:
+    rules:
+    - host: rewritetargetrootpath
+      http:
+        paths:
+        - backend:
+            serviceName: service1
+            servicePort: 80
+          path: /
+
 ---
 apiVersion: extensions/v1beta1
 kind: Ingress

provider/kubernetes/kubernetes.go

@@ -674,6 +674,12 @@ func getRuleForPath(pa extensionsv1beta1.HTTPIngressPath, i *extensionsv1beta1.I
 			return "", fmt.Errorf("rewrite-target must not be used together with annotation %q", annotationKubernetesRuleType)
 		}
 		rewriteTargetRule := fmt.Sprintf("ReplacePathRegex: ^%s(.*) %s$1", pa.Path, strings.TrimRight(rewriteTarget, "/"))
+		if pa.Path == "/" {
+			// If path = /, then just append the cap group, as if we don't cap the path as part of the regex,
+			// then when we strip the right / from the rewrite target, it ends up being missed, as removed but never returned
+			// this only happens when path = / because it is the only case where TrimRight will catch a leading /.
+			rewriteTargetRule = fmt.Sprintf("ReplacePathRegex: ^(.*) %s$1", strings.TrimRight(rewriteTarget, "/"))
+		}
 		rules = append(rules, rewriteTargetRule)
 	}
 

provider/kubernetes/kubernetes_test.go

@@ -415,6 +415,12 @@ func TestProvider_loadIngresses(t *testing.T) {
 							server("http://example.com", weight(1))),
 						lbMethod("wrr"),
 					),
+					backend("rewritetargetrootpath/",
+						servers(
+							server("http://example.com", weight(1)),
+							server("http://example.com", weight(1))),
+						lbMethod("wrr"),
+					),
 					backend("error-pages/errorpages",
 						servers(
 							server("http://example.com", weight(1)),
@@ -523,6 +529,12 @@ func TestProvider_loadIngresses(t *testing.T) {
 							route("/whitelist-source-range", "PathPrefix:/whitelist-source-range"),
 							route("test", "Host:test")),
 					),
+					frontend("rewritetargetrootpath/",
+						passHostHeader(),
+						routes(
+							route("/", "PathPrefix:/;ReplacePathRegex: ^(.*) /app$1"),
+							route("rewritetargetrootpath", "Host:rewritetargetrootpath")),
+					),
 					frontend("rewrite/api",
 						passHostHeader(),
 						routes(
@@ -596,7 +608,7 @@ func TestProvider_loadIngresses(t *testing.T) {
 						passHostHeader(),
 						redirectRegex("root2/$", "root2/root2"),
 						routes(
-							route("/", "PathPrefix:/;ReplacePathRegex: ^/(.*) /abc$1"),
+							route("/", "PathPrefix:/;ReplacePathRegex: ^(.*) /abc$1"),
 							route("root2", "Host:root2"),
 						),
 					),