PORT env var is not respected when set in .env file

[mbohgard]

What version of Next.js are you using?

12.0.7

What version of Node.js are you using?

14.17.6

What browser are you using?

Chrome

What operating system are you using?

macOS

How are you deploying your application?

N/A

Describe the Bug

Setting PORT=4000 for ex is not respected when set in .env, .env-development etc .env files.
Loggin out process.env.PORT in next.config.js is reporting the correct port (4000) but the server is still starting on port 3000 (default).
The behaviour is the same with next dev and next start.

Expected Behavior

The server should use PORT from .env files as when started with PORT=4000 next dev.

To Reproduce

1. Have a .env file in the root of the Next project with the content PORT=4000.
2. Start the Next dev server with next dev.
3. Server is starting on port 3000.

[timneutkens]

This is actually not a bug, booting the http server asap has the highest priority in next dev / next start so it happens before loading next.config.js / dotenv files. Looks like the documentation is not clear on that so we'll document it 👍

[mbohgard]

Ok, yeah, especially since you have a .env file example with PORT=8080 in it 🥴 Thanks for the quick response!

[timneutkens]

That example is constructing an external API url. But can be changed

[kachkaev]

Reading all .env* files should take less than few milliseconds, which should not be noticeable both in next dev and next start.

start server
read .env*
read next.config.js

↓

read .env*
start server
read next.config.js

I just ran PORT=4242 yarn dev to avoid clashes with another server. It worked, so I moved PORT=4242 to .env.local as I typically do for other vars. The server launched at 3000, so I got confused and ended up here 🙂

What’s the practical benefit of launching the server before loading .env? How many milliseconds do we save?

[timneutkens]

Reading all .env* files should take less than few milliseconds, which should not be noticeable both in next dev and next start.

With normal file reading in Node.js we already see it taking upward of 10ms+ per-file depending on how much is going on in the main thread, so it'll significantly slow down bootup.

[LSafer]

Will, I don't care about 1000ms so would you please add an option for those like me who don't care 😕

Also, I don't think anybody would care about 1000ms in ((production))

For development you could cache it or something like that or make it a production thing

[LSafer]

Sorry for the tuff language but I am not a native speaker and I don't know how to deliver my thoughts better than that 😅

[SCG82]

Reading all .env* files should take less than few milliseconds, which should not be noticeable both in next dev and next start.

With normal file reading in Node.js we already see it taking upward of 10ms+ per-file depending on how much is going on in the main thread, so it'll significantly slow down bootup.

@timneutkens How about adding an option to read .env before starting? #44392

[manovotny]

Good callout,@mbohgard. I've made a PR (#51063) for removing PORT=8080 from an .env example to avoid any confusion.

The documentation regarding port customization has already been updated with a note that using .env is not currently possible, as seen below.

[github-actions]

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