SSG pages re-render if middleware is being used

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System: Platform: win32 Arch: x64 Version: Windows 10 Home Binaries: Node: 14.18.0 npm: N/A Yarn: N/A pnpm: N/A Relevant packages: next: 12.2.1-canary.2 eslint-config-next: 12.2.0 react: 18.2.0 react-dom: 18.2.0

What browser are you using? (if relevant)

Chrome 103.0.5060.66

How are you deploying your application? (if relevant)

next start, Vercel

Describe the Bug

By using the new stable middleware.js at the root of the project, all pages will render twice. With the old _middleware.js, there was no similar problem. Please note that if you rename or remove middleware.js from root, it works without any issues.

Expected Behavior

Pages render only once

Link to reproduction

https://github.com/imangm/nextjs-middleware-rerender

To Reproduce

1. Clone the repo
2. Run npm run build
3. Run npm run start
4. In Chrome DevTools, go to Network tab -> Network conditions
5. Turn on Disable cache, also set Network throttling to Slow 3G to see the issue clearly
6. Open the project in chrome
7. Once the page loads, quickly scroll down, once the page is loaded once, it will load again and will automatically scroll to top
8. In the console, you can see render _app is logged twice
9. Also if you run the project using npm run dev, you can check the chrome console to see the re-render
10. A live version of the repo is available here: https://next-middleware-rerender.vercel.app/

[11koukou]

This should be addressed with high priority

[shuding]

Hi all! I’m going to verify if it’s safe to re-land #37431 and also add a test for this specific issue.

Hi @ijjk the PR above adds a validation on top of the existing feature to prevent this from happening. What is the root cause for the issue? Is it possible to have the root cause fixed instead?

The reason why it was happening in the first place is we can’t easily tell if there’s gonna be a query or not, when accessing to certain routes. If there’s a query, a re-render to update the route state is necessary to avoid hydration mismatch issues.