Fix login failure in JupyterHub 5.4

Remove the extra leading slash from `X-Reproxy-URL`.

Author: shingo78

auth-proxy/resources/htdocs/php/login.php

@@ -21,9 +21,13 @@
         $_SESSION['username'] = $username;
         $_SESSION['authtype'] = 'local';
 
-        $next_param = isset($_GET['next']) ? '?next=' . urlencode($_GET['next']) : '';
+        $login_params = array();
+        if (isset($_GET['next'])) {
+            $login_params['next'] = $_GET['next'];
+        }
+        $reproxy_url = get_reproxy_url($login_params);
         header("X-Accel-Redirect: /entrance/");
-        header("X-Reproxy-URL: ".HUB_URL.'/'.COURSE_NAME."/hub/login".$next_param);
+        header("X-Reproxy-URL: $reproxy_url");
         header("X-REMOTE-USER: $username");
 
         exit;

auth-proxy/resources/htdocs/php/lti/service.php

@@ -84,13 +84,9 @@
     if ($next) {
         $login_params['next'] = $next;
     }
+    $reproxy_url = get_reproxy_url($login_params);
 
     header("X-Accel-Redirect: /entrance/");
-    $reproxy_url = HUB_URL.'/'.COURSE_NAME."/hub/login";
-    $query = http_build_query($login_params, '', null, PHP_QUERY_RFC3986);
-    if ($query) {
-        $reproxy_url = $reproxy_url.'?'.$query;
-    }
     header("X-Reproxy-URL: $reproxy_url");
     header("X-REMOTE-USER: $username");
 } else if ($launch->is_deep_link_launch()) {

auth-proxy/resources/htdocs/php/sp.php

@@ -20,9 +20,13 @@
     session_regenerate_id(true);
     $_SESSION['authtype'] = 'saml';
     $username = get_username_from_mail_address($mail_address);
-    $next_param = isset($_GET['next']) ? '?next=' . urlencode($_GET['next']) : '';
+    $login_params = array();
+    if (isset($_GET['next'])) {
+        $login_params['next'] = $_GET['next'];
+    }
+    $reproxy_url = get_reproxy_url($login_params);
     header("X-Accel-Redirect: /entrance/");
-    header("X-Reproxy-URL: ".HUB_URL.'/'.COURSE_NAME."/hub/login".$next_param);
+    header("X-Reproxy-URL: $reproxy_url");
     header("X-REMOTE-USER: $username");
 } else {
     // redirect to message page

auth-proxy/resources/lib/functions.php

@@ -121,3 +121,19 @@ function generate_password($length = 10)
     }
     return $password;
 }
+
+function get_reproxy_url($params)
+{
+    $reproxy_url = HUB_URL;
+    if (! empty(COURSE_NAME)) {
+        $reproxy_url .= '/';
+        $reproxy_url .= COURSE_NAME;
+    }
+    $reproxy_url .= '/hub/login';
+    $query = http_build_query($params, '', null, PHP_QUERY_RFC3986);
+    if ($query) {
+        $reproxy_url .= '?';
+        $reproxy_url .= $query;
+    }
+    return $reproxy_url;
+}