getInitialProps is called multiple times using Express/Fastify

• [ x] I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

A page’s getInitialProps should only be called once per page load.

Current Behavior

Sometimes getInitialProps is called multiple times in one page load.

Steps to Reproduce (for bugs)

Minimal example app (almost identical to the next example app “custom-server-express”): https://github.com/approots/next-express-issue

To reproduce:

1. Run npm run dev and check the terminal console for multiple outputs of the console.log statement in the getInitialProps function of pages/index.js (“getInitialProps index”).
2. Or click the link to “post 2”, refresh the page, then load the index page again (localhost:3000/), and check the terminal and see multiple console.logs of “getInitialProps index”. This also happens in production.

Context

This means that API calls are being duplicated.

Your Environment

Tech	Version
next	^5.1.0
node	8.9.4
OS	Windows
browser	Chrome
express	^4.16.3

[timneutkens]

getInitialProps is only ran once per render. The only thing that I could see is that sometimes HMR kicks in and reloads the page really fast while booting up. But that’s not unexpected.

Here’s the code: https://github.com/zeit/next.js/blob/canary/server/render.js#L79

Note that the correct way to test per-render is to do curl http://localhost:3000, since then there are no other factors.

[approots]