Add Cloudflare Pages middleware to handle trailing slash redirects

[mdlinville]

Problem

Cloudflare Pages has a limitation where:

• /wandb/config/ → redirects correctly to /ref/python/sdk/functions/init/ (via _redirects)
• /wandb/config → returns 404 (doesn't match the redirect rule)

Recently, we discovered that this results in a Google Search Console report with over 1000 404s that never hit the Cloudflare redirects at all.

Solution

We've implemented a Cloudflare Pages Function middleware that automatically adds trailing slashes to URLs before they're processed by the redirect rules.

How it works

1. The middleware intercepts all GET/HEAD requests
2. For URLs without trailing slashes (and not file extensions or system files):
   • It checks if adding a slash would match a redirect rule
   • If yes, it redirects to the URL with a trailing slash
3. The browser then follows the redirect and hits the actual redirect rule

Example flow

1. User visits: /wandb/config
2. Middleware redirects to: /wandb/config/ (301)
3. _redirects rule matches and redirects to: /ref/python/sdk/functions/init/ (301)
4. Final destination served: /ref/python/sdk/functions/init/

Implementation

Files created/modified:

1. /functions/_middleware.js - The edge function that handles trailing slash redirects
2. /public/_routes.json - Configuration to ensure the middleware runs on all routes

Tested Scenarios

✅ Working correctly:

1. Redirect rules without trailing slashes

   • /wandb/config → /wandb/config/ → /ref/python/sdk/functions/init/
   • Preserves query parameters: /wandb/config?test=param → /wandb/config/?test=param

2. Files with extensions (not redirected)

   • /wandb/config.html → 404 (no redirect)
   • /style.css → served as-is
   • /script.js → served as-is

3. Paths already with trailing slashes (passed through)

   • /index/ → processed normally
   • /wandb/config/ → triggers redirect rule directly

4. System files (not redirected)

   • /robots.txt → served as-is
   • /favicon.ico → served as-is

5. Directory paths

   • /guides → /guides/ (when directory exists)

6. Special paths

   • / → works correctly (already has slash)
   • /path.with.dots → processed normally (no common file extension)

Edge cases handled:

• Query parameters are preserved during redirect
• Hash fragments are preserved during redirect
• Only common file extensions skip the middleware (.html, .css, .js, etc.)
• Paths with dots but uncommon extensions are processed normally

Deployment Instructions

The middleware will be automatically deployed to production when this PR is merged. These files are the key:

• /functions/_middleware.js - The middleware code
• /public/_routes.json - Routes configuration (optional, but recommended)

Testing

This has been tested locally by using Wrangler, since it's not so easy to test it in the Hugo layer.

The middleware is deployed in this PR's preview build for easy testing. The Cloudflare build logs in this PR show:

13:33:47.656 | Successfully read wrangler.toml file.
-- | --
13:33:47.657 | Found Functions directory at /functions. Uploading.
13:33:47.665 | ⛅️ wrangler 3.101.0
13:33:47.665 | -------------------
13:33:48.705 | ✨ Compiled Worker successfully

Test these URLs without the trailing slash, and they should redirect as described:

From	To
https://cloudflare-trailing-slash-ed.docodile.pages.dev/wandb/config	https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/python/sdk/functions/init/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/library/init	https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/python/sdk/functions/init/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/artifacts/api	https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/python/artifact/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/sweeps/quickstart	https://cloudflare-trailing-slash-ed.docodile.pages.dev/guides/sweeps/walkthrough/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/frameworks/pytorch	https://cloudflare-trailing-slash-ed.docodile.pages.dev/guides/integrations/pytorch/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/library/hyperparameter-sweeps	https://cloudflare-trailing-slash-ed.docodile.pages.dev/guides/sweeps/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/guides/self-hosted	https://cloudflare-trailing-slash-ed.docodile.pages.dev/guides/hosting/hosting-options/self-managed/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/company/company-faq	https://cloudflare-trailing-slash-ed.docodile.pages.dev/support/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/data_types	https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/python/data-types/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/weave/boards	https://cloudflare-trailing-slash-ed.docodile.pages.dev/guides/app/features/panels/query-panels/
https://cloudflare-trailing-slash-ed.docodile.pages.dev/wandb/config?test=param	https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/python/sdk/functions/init/?test=param (is a no-op but preserves the query parameter
https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/release-notes/0.73#v0731	https://cloudflare-trailing-slash-ed.docodile.pages.dev/ref/release-notes/0.73/#v0731 (preeserves the anchor)

If you are observing in the browser inspector or the Cloudflare logs, each test should result in two redirects:

1. 301 redirect adding the trailing slash (example: /wandb/config → /wandb/config/)
2. 301 redirect to the final destination (example: /wandb/config/ → /ref/python/sdk/functions/init/)

[cloudflare-workers-and-pages]

Deploying docs with    Cloudflare Pages

Latest commit:	1cef038
Status:	✅  Deploy successful!
Preview URL:	https://7cf51575.docodile.pages.dev
Branch Preview URL:	https://cloudflare-trailing-slash-ed.docodile.pages.dev

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