TanStack Router: Fixing Trailing Slash With Splat Routes

Hey guys! Today, we're diving into a quirky issue in TanStack Router that some of you might have stumbled upon: the curious case of trailing slashes when using splat routes. Specifically, we're talking about when the trailingSlash option doesn't quite behave as expected with splat routes. Let's break down the problem, see how to reproduce it, and understand the expected behavior.

The Bug: Trailing Slashes and Splat Routes

So, what's the deal? Imagine you've defined a route with a splat, something like some-testing.route.$.tsx. You'd expect that the trailingSlash option would consistently enforce your preferred style—either always adding a trailing slash or always removing it. However, there's a snag. When you use a <Link> component like this:

<Link to="/some-testing/route/{{content}}quot; params={{ _splat: "" }} />

You might notice that the generated path stubbornly remains /some-testing/route/, regardless of whether your trailingSlash option is set to never. And if you try to get clever and use {{ _splat: undefined }}, you end up with the even more perplexing /some-testing/route/undefined. Not ideal, right?

Why This Matters

For those unfamiliar, a splat route (or catch-all route) is a route that can match any number of path segments. They're super useful for things like blog posts, documentation pages, or any situation where you have a variable number of segments in your URL. Getting the trailing slash right is crucial for SEO, consistency, and just plain aesthetics. Search engines often treat URLs with and without trailing slashes as different pages, which can lead to duplicate content issues. Plus, a consistent URL structure makes your site look more professional.

Diving Deeper: The Technical Details

The root cause of this issue lies in how TanStack Router handles the _splat parameter when generating the path. When an empty string is passed as the _splat value, the router incorrectly adds a trailing slash, ignoring the trailingSlash configuration. Similarly, when undefined is passed, it's rendered as the string "undefined" in the URL, which is definitely not the intended behavior. This inconsistency can lead to unexpected results and a less-than-ideal user experience.

The Impact on SEO and User Experience

The implications of this bug extend beyond mere aesthetics. Search engine optimization (SEO) can be significantly affected, as search engines may interpret URLs with and without trailing slashes as distinct pages, potentially leading to duplicate content issues and diluted search rankings. From a user experience perspective, inconsistent URL structures can create confusion and a sense of disorganization, undermining the overall credibility of the website. Therefore, addressing this issue is not just about fixing a minor visual glitch but about ensuring a robust and user-friendly navigation system.

Reproducing the Bug

Want to see it in action? Here's how you can reproduce the bug:

1. Open the StackBlitz example: https://stackblitz.com/edit/github-oehqi8ag-yf2ynpjd?file=src%2Froutes%2F__root.tsx
2. Hover over the "Trailing Slash" link: Notice that the href attribute always ends with a slash, even though the trailingSlash option is set to never.

It's a small thing, but it highlights the issue perfectly!

Expected Behavior

Ideally, the trailingSlash option should be respected, no matter what. If it's set to never, the router should always remove the trailing slash. And, of course, passing undefined as the _splat value should result in a clean URL without any "undefined" strings.

The Importance of Consistent URL Structures

Consistency in URL structures is paramount for several reasons. First and foremost, it enhances SEO. Search engines like Google use URLs to understand the content and structure of a website. When URLs are consistent and predictable, it becomes easier for search engines to crawl and index the site effectively. Duplicate content issues, which can negatively impact search rankings, are also minimized. Secondly, a consistent URL structure improves the user experience. Users are more likely to trust and engage with a website that presents a clean and organized appearance. Predictable URLs make it easier for users to navigate the site, share links, and bookmark pages. Additionally, consistent URLs facilitate easier integration with third-party tools and services, such as analytics platforms and social media sharing buttons.

Platform Information

Here's the setup where this bug was observed:

• Router/Start Version: 1.132.33
• OS: macOS
• Browser: Chrome
• Browser Version: 140.0.7339
• Bundler: Vite
• Bundler Version: 7.1.17

Possible Solutions and Workarounds

While we await a fix from the TanStack Router team, here are a few workarounds you can implement to mitigate the issue:

1. Conditional Rendering: You can use conditional rendering to avoid passing an empty string or undefined as the _splat value. For example, you can check if the _splat value is empty and, if so, avoid rendering the <Link> component or use a different route.

   {_splat ? (
   <Link to="/some-testing/route/{{content}}quot; params={{ _splat: _splat }} />
   ) : (
   <Link to="/some-testing/route" />
   )}
   

2. Custom Path Generation: You can create a custom function to generate the path manually, ensuring that the trailing slash is correctly handled based on your trailingSlash option.

   const generatePath = (splatValue: string | undefined) => {
   let path = "/some-testing/route";
   if (splatValue) {
   path += `/${splatValue}`;
   }
   if (trailingSlash === "never" && path.endsWith("/")) {
   path = path.slice(0, -1);
   }
   return path;
   };
   
   <Link to={generatePath(_splat)} />
   

3. Post-Processing: After the path is generated, you can use a function to remove the trailing slash if it exists and the trailingSlash option is set to never.

   const removeTrailingSlash = (path: string) => {
   if (trailingSlash === "never" && path.endsWith("/")) {
   return path.slice(0, -1);
   }
   return path;
   };
   
   <Link to={removeTrailingSlash(router.generatePath("/some-testing/route/{{content}}quot;, { _splat: _splat }))} />
   

These workarounds can help you maintain a consistent URL structure while waiting for a permanent fix.

Wrapping Up

So, there you have it! A little quirk in TanStack Router's handling of trailing slashes with splat routes. While it's a minor issue, understanding these nuances can save you some headaches and ensure your URLs are clean and consistent.

Keep an eye on the TanStack Router repository for updates, and happy routing!

For more information on TanStack Router and its features, visit the official documentation: TanStack Router Documentation.