fix: getFileExtension returns raw URL path instead of null for URLs without file extensions

[cax6505]

Description

In @dub/utils, the getFileExtension(url) helper function incorrectly returns the full URL pathname (e.g. "/AVATAR" or "/API/V1/USERS") when given a URL that does not contain a file extension.

Reproduction

import { getFileExtension } from "@dub/utils";

console.log(getFileExtension("https://dub.co/avatar")); 
// Output: "/AVATAR" (Expected: null)

console.log(getFileExtension("https://dub.co/api/v1/users")); 
// Output: "/API/V1/USERS" (Expected: null)

Cause

In packages/utils/src/functions/urls.ts:

export const getFileExtension = (url: string): string | null => {
  try {
    const pathname = new URL(url).pathname;
    const extension = pathname.split(".").pop(); // When pathname has no ".", returns entire pathname
    return extension ? extension.toUpperCase() : null;
  } catch { ... }
};

When pathname has no dot (.), pathname.split(".") yields ["/avatar"]. Calling .pop() returns "/avatar", which is truthy, so it returns "/AVATAR".

Impact

In ResourceCard (resources/page.tsx), brand logos with extensionless asset URLs display badge labels like "/LOGO · 24 KB" instead of "Unknown · 24 KB".

Proposed Fix

Verify that the extracted filename actually contains a dot before returning the extension:

export const getFileExtension = (url: string): string | null => {
  try {
    const pathname = new URL(url).pathname;
    const filename = pathname.split("/").pop() || "";
    if (!filename.includes(".")) return null;
    const extension = filename.split(".").pop();
    return extension && extension !== filename ? extension.toUpperCase() : null;
  } catch {
    return null;
  }
};

[linear]

ENG-1724

[cax6505]

I've implemented the fix and added unit tests for this issue on my fork branch:

https://github.com/cax6505/dub/tree/fix/get-file-extension-null-check

Since PR creation is currently restricted to collaborators, please let me know if you can assign this to me or invite me to submit the PR!

[ankit-pandit07]

Hi! I’ve implemented a fix for this issue in my fork.

The fix:

• returns null when a URL has no file extension
• only treats the final filename segment as the extension
• handles query strings/hashes correctly
• adds tests for the relevant edge cases

All targeted tests are passing.

My branch is ready:
https://github.com/ankit-pandit07/dub/tree/fix/get-file-extension

However, GitHub is currently preventing me from opening a PR because PR creation is restricted to repository collaborators.

Could you please enable PRs from forks for me, or let me know how you’d like me to submit the change?

Thanks!