Issue #1503146: drupal_is_front_page() does not detect Front Page in some cases

core/lib/Drupal/Core/Path/PathMatcher.php

@@ -91,17 +91,27 @@ public function matchPath($path, $patterns) {
   public function isFrontPage() {
     // Cache the result as this is called often.
     if (!isset($this->isCurrentFrontPage)) {
-      $this->isCurrentFrontPage = FALSE;
-      // Ensure that the code can also be executed when there is no active
-      // route match, like on exception responses.
-      if ($this->routeMatch->getRouteName()) {
-        $url = Url::fromRouteMatch($this->routeMatch);
-        $this->isCurrentFrontPage = ($url->getRouteName() && '/' . $url->getInternalPath() === $this->getFrontPagePath());
-      }
+      $this->isCurrentFrontPage = $this->checkFrontPage();
     }
     return $this->isCurrentFrontPage;
   }
 
+  /**
+   * Checks if the current page is the front page, without caching the result.
+   *
+   * @return bool
+   *   TRUE if the current page is the front page.
+   */
+  protected function checkFrontPage() {
+    // Ensure that the code can also be executed when there is no active
+    // route match, like on exception responses.
+    if ($this->routeMatch->getRouteName()) {
+      $url = Url::fromRouteMatch($this->routeMatch);
+      return ($url->getRouteName() && '/' . $url->getInternalPath() === $this->getFrontPagePath());
+    }
+    return FALSE;
+  }
+
   /**
    * Gets the current front page path.
    *