fix(backend): redirect to slash

If listen.prefix is set to /foo we should redirect /foo => /foo/

Fixes 3084

cmd/karma/main.go

@@ -60,15 +60,14 @@ var (
 func getViewURL(sub string) string {
 	var fixedSub string
 	fixedSub = sub
-	if !strings.HasPrefix(sub, "/") {
+	if sub != "" && !strings.HasPrefix(sub, "/") {
 		fixedSub = "/" + sub
 	}
 
 	var fixedPrefix string
-	fixedPrefix = config.Config.Listen.Prefix
-	if config.Config.Listen.Prefix != "" && !strings.HasPrefix(config.Config.Listen.Prefix, "/") {
-		fixedPrefix = "/" + config.Config.Listen.Prefix
-	}
+	fixedPrefix = strings.TrimPrefix(config.Config.Listen.Prefix, "/")
+	fixedPrefix = strings.TrimSuffix(fixedPrefix, "/")
+	fixedPrefix = "/" + fixedPrefix + "/"
 
 	u := path.Join(fixedPrefix, fixedSub)
 	if strings.HasSuffix(fixedSub, "/") && !strings.HasSuffix(u, "/") {
@@ -127,6 +126,9 @@ func setupRouter(router *chi.Mux, historyPoller *historyPoller) {
 		router.Use(basicAuth(users, allowAuthBypass))
 	}
 
+	if config.Config.Listen.Prefix != "/" {
+		router.Get(getViewURL(""), redirectIndex)
+	}
 	router.Get(getViewURL("/"), index)
 	router.Get(getViewURL("/health"), pong)
 	router.Get(getViewURL("/robots.txt"), robots)

cmd/karma/views.go

@@ -94,6 +94,10 @@ func pushPath(w http.ResponseWriter, path string) {
 	}
 }
 
+func redirectIndex(w http.ResponseWriter, r *http.Request) {
+	http.Redirect(w, r, r.URL.Path+"/", http.StatusMovedPermanently)
+}
+
 func index(w http.ResponseWriter, r *http.Request) {
 	noCache(w)
 	pushPath(w, getViewURL("/custom.css"))

cmd/karma/views_test.go

@@ -103,28 +103,102 @@ func TestHealthPrefix(t *testing.T) {
 }
 
 func TestIndex(t *testing.T) {
-	mockConfig()
-	r := testRouter()
-	setupRouter(r, nil)
-	req := httptest.NewRequest("GET", "/", nil)
-	resp := httptest.NewRecorder()
-	r.ServeHTTP(resp, req)
-	if resp.Code != http.StatusOK {
-		t.Errorf("GET / returned status %d", resp.Code)
+	type testCaseT struct {
+		prefix   string
+		request  string
+		status   int
+		redirect string
 	}
-}
 
-func TestIndexPrefix(t *testing.T) {
-	os.Setenv("LISTEN_PREFIX", "/prefix")
-	defer os.Unsetenv("LISTEN_PREFIX")
-	mockConfig()
-	r := testRouter()
-	setupRouter(r, nil)
-	req := httptest.NewRequest("GET", "/prefix/", nil)
-	resp := httptest.NewRecorder()
-	r.ServeHTTP(resp, req)
-	if resp.Code != http.StatusOK {
-		t.Errorf("GET /prefix/ returned status %d", resp.Code)
+	testCases := []testCaseT{
+		{
+			prefix:  "",
+			request: "/",
+			status:  200,
+		},
+		{
+			prefix:  "",
+			request: "/alerts.json",
+			status:  200,
+		},
+		{
+			prefix:  "/",
+			request: "/",
+			status:  200,
+		},
+		{
+			prefix:  "/",
+			request: "/alerts.json",
+			status:  200,
+		},
+		{
+			prefix:  "/prefix",
+			request: "/",
+			status:  404,
+		},
+		{
+			prefix:  "/prefix",
+			request: "/alerts.json",
+			status:  404,
+		},
+		{
+			prefix:  "/prefix",
+			request: "/prefix/",
+			status:  200,
+		},
+		{
+			prefix:  "/prefix",
+			request: "/prefix/alerts.json",
+			status:  200,
+		},
+		{
+			prefix:   "/prefix",
+			request:  "/prefix",
+			status:   301,
+			redirect: "/prefix/",
+		},
+		{
+			prefix:   "/prefix/",
+			request:  "/prefix",
+			status:   301,
+			redirect: "/prefix/",
+		},
+		{
+			prefix:  "/prefix/",
+			request: "/prefix/",
+			status:  200,
+		},
+		{
+			prefix:  "/prefix/",
+			request: "/prefix/alerts.json",
+			status:  200,
+		},
+	}
+
+	defer func() {
+		config.Config.Listen.Prefix = "/"
+	}()
+
+	for _, tc := range testCases {
+		t.Run(fmt.Sprintf("prefix=%s request=%s status=%d", tc.prefix, tc.request, tc.status), func(t *testing.T) {
+			os.Setenv("LISTEN_PREFIX", tc.prefix)
+			defer os.Unsetenv("LISTEN_PREFIX")
+			mockConfig()
+			r := testRouter()
+			setupRouter(r, nil)
+			req := httptest.NewRequest("GET", tc.request, nil)
+			resp := httptest.NewRecorder()
+			r.ServeHTTP(resp, req)
+			if resp.Code != tc.status {
+				t.Errorf("GET %s returned status %d, expected %d", tc.request, resp.Code, tc.status)
+				return
+			}
+			if resp.Code/100 == 3 && tc.status/100 == 3 {
+				if resp.Header().Get("Location") != tc.redirect {
+					t.Errorf("GET %s returned redirect to %s, expected %s", tc.request, resp.Header().Get("Location"), tc.redirect)
+				}
+			}
+		})
 	}
 }