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Add deprecation warning to Runtime config #84168

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Merged
devjiwonchoi merged 5 commits into from
Oct 8, 2025
Merged

Add deprecation warning to Runtime config #84168

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50a8179
Add deprecation warning to Runtime config
devjiwonchoi Sep 24, 2025
83bac4b
add closing parenthesis to docs link
devjiwonchoi Sep 24, 2025
89d7c0a
add deprecated note to setConfig & getConfig
devjiwonchoi Sep 25, 2025
192ef57
Add warning to the import site
devjiwonchoi Oct 8, 2025
5a50696
Add test
devjiwonchoi Oct 8, 2025
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13 changes: 12 additions & 1 deletion packages/next/config.js
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Original file line number Diff line number Diff line change
@@ -1 +1,12 @@
module.exports = require('./dist/shared/lib/runtime-config.external')
let hasWarned = false

module.exports = (() => {
if (!hasWarned) {
console.warn(
// ANSI code aligns with Next.js warning style from picocolors.
' \x1b[33m\x1b[1m⚠\x1b[22m\x1b[39m Runtime config is deprecated and will be removed in Next.js 16. Please remove the usage of "next/config" from your project.'
)
hasWarned = true
}
return require('./dist/shared/lib/runtime-config.external')
})()
6 changes: 4 additions & 2 deletions packages/next/src/server/config-shared.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1118,14 +1118,16 @@ export interface NextConfig {
/**
* Add public (in browser) runtime configuration to your app
*
* @see [Runtime configuration](https://nextjs.org/docs/pages/api-reference/config/next-config-js/runtime-configuration
* @see [Runtime configuration](https://nextjs.org/docs/pages/api-reference/config/next-config-js/runtime-configuration)
* @deprecated Runtime config is deprecated and will be removed in Next.js 16.
*/
publicRuntimeConfig?: { [key: string]: any }

/**
* Add server runtime configuration to your app
*
* @see [Runtime configuration](https://nextjs.org/docs/pages/api-reference/config/next-config-js/runtime-configuration
* @see [Runtime configuration](https://nextjs.org/docs/pages/api-reference/config/next-config-js/runtime-configuration)
* @deprecated Runtime config is deprecated and will be removed in Next.js 16.
*/
serverRuntimeConfig?: { [key: string]: any }

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13 changes: 13 additions & 0 deletions packages/next/src/server/config.ts
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Expand Up @@ -109,6 +109,19 @@ function checkDeprecations(
silent: boolean,
dir: string
) {
warnOptionHasBeenDeprecated(
userConfig,
'publicRuntimeConfig',
`Runtime config is deprecated and the \`publicRuntimeConfig\` configuration option will be removed in Next.js 16.`,
silent
)
warnOptionHasBeenDeprecated(
userConfig,
'serverRuntimeConfig',
`Runtime config is deprecated and the \`serverRuntimeConfig\` configuration option will be removed in Next.js 16.`,
silent
)
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@ijjk ijjk Sep 24, 2025

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Do we have any tests ensuring these are logged as expected?

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@devjiwonchoi devjiwonchoi Sep 24, 2025

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For deprecation warnings no, can follow up

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@devjiwonchoi devjiwonchoi Sep 25, 2025

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Oh we do have test/e2e/deprecation-warnings/deprecation-warnings.test.ts

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@devjiwonchoi devjiwonchoi Oct 8, 2025

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Added tests


if (userConfig.experimental?.dynamicIO !== undefined) {
warnOptionHasBeenDeprecated(
userConfig,
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6 changes: 6 additions & 0 deletions packages/next/src/shared/lib/runtime-config.external.ts
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Original file line number Diff line number Diff line change
@@ -1,9 +1,15 @@
let runtimeConfig: any

/**
* @deprecated Runtime config is deprecated and will be removed in Next.js 16.
*/
export default () => {
return runtimeConfig
}
Comment on lines +3 to 8
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@eps1lon eps1lon Sep 25, 2025 •
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Can we do a runtime warning here as well?

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@devjiwonchoi devjiwonchoi Sep 25, 2025

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We have internals that call this resulting warning regardless of whether the users set the value on the config. 🤔

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@devjiwonchoi devjiwonchoi Sep 25, 2025

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We can do

if (!process.env.__NEXT_TEST_MODE) {

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@eps1lon eps1lon Sep 25, 2025

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Where do we export these methods? Can the publicly available function just wrap this one with a runtime warning? There we should set the @deprecated instead of on the internal one that we want to continue using anyway.

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@devjiwonchoi devjiwonchoi Sep 25, 2025 •
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We can modify from here

next.js/packages/next/config.d.ts

Lines 1 to 3 in f9248ea

import getConfig from './dist/shared/lib/runtime-config.external'
export * from './dist/shared/lib/runtime-config.external'
export default getConfig

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@devjiwonchoi devjiwonchoi Oct 8, 2025 •
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There we should set the @deprecated instead of on the internal one that we want to continue using anyway.

We're not going to use it when we remove; the internal usages are setConfig for the user to use when getConfig.


/**
* @deprecated Runtime config is deprecated and will be removed in Next.js 16.
*/
export function setConfig(configValue: any): void {
runtimeConfig = configValue
}
8 changes: 8 additions & 0 deletions test/e2e/app-dir/deprecation-warning-runtime-config/app/layout.tsx
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@@ -0,0 +1,8 @@
import { ReactNode } from 'react'
export default function Root({ children }: { children: ReactNode }) {
return (
<html>
<body>{children}</body>
</html>
)
}
6 changes: 6 additions & 0 deletions test/e2e/app-dir/deprecation-warning-runtime-config/app/page.tsx
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@@ -0,0 +1,6 @@
import getConfig from 'next/config'

export default function Page() {
getConfig()
return <p>hello world</p>
}
16 changes: 16 additions & 0 deletions ...e2e/app-dir/deprecation-warning-runtime-config/deprecation-warning-runtime-config.test.ts
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@@ -0,0 +1,16 @@
import { nextTestSetup } from 'e2e-utils'

describe('deprecation-warning-runtime-config', () => {
const { next } = nextTestSetup({
files: __dirname,
})

it('should warn when imported "next/config" module', async () => {
// Navigate to "/" for dev server to execute the code
await next.browser('/')

expect(next.cliOutput).toContain(
'Runtime config is deprecated and will be removed in Next.js 16. Please remove the usage of "next/config" from your project.'
)
})
})
13 changes: 13 additions & 0 deletions test/e2e/app-dir/deprecation-warning-runtime-config/next.config.js
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@@ -0,0 +1,13 @@
/**
* @type {import('next').NextConfig}
*/
const nextConfig = {
publicRuntimeConfig: {
foo: 'bar',
},
serverRuntimeConfig: {
foo: 'bar',
},
}

module.exports = nextConfig
8 changes: 8 additions & 0 deletions test/e2e/deprecation-warnings/deprecation-warnings.test.ts
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Expand Up @@ -32,6 +32,14 @@ describe('deprecation-warnings', () => {
// Should warn about experimental.instrumentationHook
expect(logs).toContain('experimental.instrumentationHook')
expect(logs).toContain('no longer needed')

// Should warn about publicRuntimeConfig
expect(logs).toContain('publicRuntimeConfig')
expect(logs).toContain('will be removed in Next.js 16')

// Should warn about serverRuntimeConfig
expect(logs).toContain('serverRuntimeConfig')
expect(logs).toContain('will be removed in Next.js 16')
})
})
})
7 changes: 7 additions & 0 deletions test/e2e/deprecation-warnings/fixtures/with-deprecated-config/next.config.js
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@@ -1,6 +1,13 @@
/** @type {import('next').NextConfig} */
module.exports = {
// Explicitly configure deprecated options
experimental: {
instrumentationHook: true,
},
publicRuntimeConfig: {
foo: 'bar',
},
serverRuntimeConfig: {
foo: 'bar',
},
}
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