Vercel
Custom preview domain sets NEXT_PUBLIC_VERCEL_ENV to 'production' #775
Replies: 2 comments 10 replies
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Thanks for sharing this writeup @karmaniverous, and I'm sorry you're running into this problem. I was not able to reproduce the issue in my own project with two different custom domains (one using CNAME Record and the other using Vercel nameservers). I have a couple of initial ideas, though you may have already thought of them:
If anyone else has run into this problem with preview environment variables, I hope they will share their experience here as well! This is not something I have seen before. Curious to understand what is happening to cause this behavior. |
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We had this problem too. We're not using Vercel CLI or the GitHub integration to deploy to our preview branch, which we have named "staging." We want to use process.env.VERCEL_ENV while rendering a custom _document.js in our next.js app in order to add a noindex,nofollow meta tag to the tag; however, process.env.VERCEL_ENV was always 'production' in both preview and production. (We added a comment to our inline google-tag-manager script to show the value, seen below in the html snippet.) Now here's the weird part: Our staging subdomain was "signup.staging" when we observed process.env.VERCEL_ENV always being "production." Then on a hunch, we changed the subdomain to "signup-staging" so there were only 3 segments to the hostname (for example, "signup-staging.example.com" For some reason, this change fixed the issue. Now process.env.VERCEL_ENV === 'preview' at signup-staging.example.com and "production" at signup.example.com export default class MyDocument extends Document {
render() {
return (
<Html lang='en'>
<Head>
{process.env.VERCEL_ENV !== 'production' && (
<meta name='robots' content='noindex,nofollow' />
)}
<Script id='google-tag-manager' strategy='beforeInteractive'>
{`
(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','GTM-XXXXXX');
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'UA-99999999-1', {'transport_type': 'image'});
// VERCEL_ENV = "${process.env.VERCEL_ENV}"
`}
</Script> |
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I've submitted a ticket under our Pro plan. The case number is 00108888. |
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Thanks for sharing the ticket number! I'm confused about how your project is being built and deployed. You said that you are not using Vercel CLI, deploy hooks, or the GitHub integration to deploy. Are you using a CI pipeline, Vercel API, or another method? I need to know how the project is being deployed so I can identify possible points of failure for the environment variables. 🙏 |
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As I wrote previously, "To deploy any changes at all, we just push the entire monorepo to main or staging for production and preview respectively." Each project has the monorepo git repo connected to it. |
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Thank you for being patient with all of my questions! I asked the team to help look into this problem and I wanted to be sure we have the right info. Someone on the team responded to your ticket. You'll be able to share deployment information less publicly there and I think that will make detailed debugging conversations a little more comfortable. One idea that was suggested is monorepo caching. Have you tried |
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no we'll try that. thanks! |
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I opened a ticket on this one but there doesn't seem to be a way to link back to it, so I thought I would also add a discussion here. Here's a full writeup of the issue along with my workaround.
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