[Bug]: NextJS server page query param is not an array as expected

[ericpias]

Summary

I am using NextJs 13.4 with page routing. Using useRouter to get url query params. Specifying a query param twice and expect that param to be an array in code. Using a NextJS prod optimized build locally, it works as expected. When deployed in netlify, the param is a string (comma separated list) in a SERVER page. In a client page it is an array as expected, even when netlify deployed.

I have so far not come up with a work-around so kind of stuck. Need to use a server page here. Thanks.

Fastest replication steps are to deploy my public repo below. Then try the following. It will display the results.
https://your_deploy_id.netlify.app/?testParam=Test123&testParam=Testabc&testParam=890
https://your_deploy_id.netlify.app/clientpage?testParam=Test123&testParam=Testabc&testParam=890

My active deployment is:
https://main--coruscating-starlight-6bfcb7.netlify.app/?testParam=Test123&testParam=Testabc&testParam=890

Which shows:
Server Page
testParam should be a string if only supplied once in the URL query params. Otherwise, it should be an array.
(Server Page) testParam is a string: Test123, Testabc, 890
Client Component
(Client Component) testParam is a string: Test123, Testabc, 890

Whereas
https://main--coruscating-starlight-6bfcb7.netlify.app/clientpage?testParam=Test123&testParam=Testabc&testParam=890

Shows:
Client Page

testParam should be a string if only supplied once in the URL query params. Otherwise, it should be an array.
(Client page) testParam is an array: [Test123, Testabc, 890]
Client Component
(Client Component) testParam is an array: [Test123, Testabc, 890]

A link to a reproduction repository

https://github.com/ericpias/nextjs-query-param-bug

Expected Result

The param specified twice on the url should always be an array.

Actual Result

The param specified twice on the url is a string (comma separated list) in a SERVER page (netlify deployment only).

Steps to reproduce

Deploy the repo above and then hit the two urls above.

Next Runtime version

13.4.8

Is your issue related to the app directory?

• Yes, I am using the app directory

More information about your build

• I am building using the CLI
• I am building using file-based configuration (netlify.toml)

What OS are you using?

None

Your netlify.toml file

`netlify.toml`

# Paste content of your `netlify.toml` file here

Your public/_redirects file

`_redirects`

# Paste content of your `_redirects` file here

Your next.config.js file

/** @type {import('next').NextConfig} */
const nextConfig = {
reactStrictMode: true,
}

module.exports = nextConfig

Builds logs (or link to your logs)

8:08:16 AM: build-image version: 3ffff9df3d5419545acc1b673a54de348174406d (focal)
8:08:16 AM: buildbot version: b7c750d620b9b2152f8e19c422dafe43d6369c47
8:08:16 AM: Building without cache
8:08:16 AM: Starting to prepare the repo for build
8:08:16 AM: No cached dependencies found. Cloning fresh repo
8:08:16 AM: git clone --filter=blob:none https://github.com/ericpias/nextjs-query-param-bug
8:08:17 AM: Preparing Git Reference refs/heads/main
8:08:18 AM: Starting to install dependencies
8:08:18 AM: Python version set to 3.8
8:08:18 AM: Attempting Ruby version 2.7.2, read from environment
8:08:19 AM: Using Ruby version 2.7.2
8:08:19 AM: Started restoring cached go cache
8:08:19 AM: Finished restoring cached go cache
8:08:20 AM: go version go1.19.13 linux/amd64
8:08:21 AM: Using PHP version 8.0
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8:08:22 AM: Finished restoring cached build plugins
8:08:22 AM: Started restoring cached corepack dependencies
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8:08:22 AM: No yarn workspaces detected
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8:08:22 AM: Finished restoring cached node modules
8:08:23 AM: Installing npm packages using Yarn version 1.22.19
8:08:23 AM: yarn install v1.22.19
8:08:23 AM: warning package-lock.json found. Your project contains lock files generated by tools other than Yarn. It is advised not to mix package managers in order to avoid resolution inconsistencies caused by unsynchronized lock files. To clear this warning, remove package-lock.json.
8:08:23 AM: [1/4] Resolving packages...
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8:08:32 AM: [3/4] Linking dependencies...
8:08:34 AM: [4/4] Building fresh packages...
8:08:34 AM: Done in 11.33s.
8:08:34 AM: npm packages installed using Yarn
8:08:35 AM: Successfully installed dependencies
8:08:35 AM: Starting build script
8:08:36 AM: Detected 1 framework(s)
8:08:36 AM: "next" at version "13.4.8"
8:08:36 AM: Section completed: initializing
8:08:37 AM: ​
8:08:37 AM: Netlify Build
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8:08:37 AM: ​
8:08:37 AM: ❯ Version
8:08:37 AM: @netlify/build 29.28.2
8:08:37 AM: ​
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8:08:37 AM: buildId: 6560a03fa9a7b11f62e3ac7b
8:08:37 AM: deployId: 6560a03fa9a7b11f62e3ac7d
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8:08:37 AM: ❯ Current directory
8:08:37 AM: /opt/build/repo
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8:08:37 AM: ❯ Config file
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8:08:37 AM: ​
8:08:37 AM: ❯ Context
8:08:37 AM: production
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8:08:37 AM: ❯ Installing plugins
8:08:37 AM: - @netlify/[email protected]
8:08:50 AM: ​
8:08:50 AM: ❯ Using Next.js Runtime - v4.41.2
8:08:51 AM: ​
8:08:51 AM: @netlify/plugin-nextjs (onPreBuild event)
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8:08:52 AM: No Next.js cache to restore.
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8:08:52 AM: Build command from Netlify app
8:08:52 AM: ────────────────────────────────────────────────────────────────
8:08:52 AM: ​
8:08:52 AM: $ npm run build
8:08:52 AM: > [email protected] build
8:08:52 AM: > next build
8:08:52 AM: - warn No build cache found. Please configure build caching for faster rebuilds. Read more: https://nextjs.org/docs/messages/no-cache
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8:08:59 AM: - info Compiled successfully
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8:09:10 AM: ┌ λ / 842 B 75.5 kB
8:09:10 AM: ├ /_app 0 B 74.6 kB
8:09:10 AM: ├ ○ /404 182 B 74.8 kB
8:09:10 AM: ├ λ /api/hello 0 B 74.6 kB
8:09:10 AM: └ ○ /clientPage 826 B 75.4 kB
8:09:10 AM: + First Load JS shared by all 74.6 kB
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8:09:10 AM: ​
8:09:10 AM: (build.command completed in 18s)
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8:09:10 AM: @netlify/plugin-nextjs (onBuild event)
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8:09:10 AM: ​
8:09:10 AM: Moving static page files to serve from CDN...
8:09:10 AM: Moved 3 files to CDN
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Function logs

Function logs

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.next JSON files

generated .next JSON files

# Paste file contents here. Please check there isn't any private info in them
# You can either build locally, or download the deploy from Netlify by clicking the arrow next to the deploy time.

[pozhega]

@ericpias Have you managed to solve this issue? I have the same problem but using Next.js 12.3.1.

[serhalp]

Hi @ericpias @pozhega

The team at Netlify have now released the new v5 Next.js runtime which has support for both pages and app router, on-demand and time-based revalidation, automatic fine-grained cache control, and automatic image optimization using Netlify's image CDN.

You can find the documentation and additional information on the new runtime here: Next.js on Netlify

The v4 runtime is now in the maintenance support phase with no new features being added. Occasional bug fixes and security patches will be applied when needed.

Thanks!