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test: add locale assertions for middleware handling #2984

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f0d47c1
test: add locale assertions for middleware handling
pieh Jun 27, 2025
a623845
test: adjust fixture to use NextUrl to preserve locale when rewriting
pieh Jun 30, 2025
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28 changes: 24 additions & 4 deletions tests/e2e/edge-middleware.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -63,11 +63,13 @@ test.describe('json data', () => {
describeLabel: 'NextResponse.next() -> getServerSideProps page',
selector: 'NextResponse.next()#getServerSideProps',
jsonPathMatcher: '/link/next-getserversideprops.json',
assertLocale: true,
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Only getServerSideProps and getStaticProps even have access to locale and "fully static page" cases just don't have access to it so asserting locale is optional check enabled to cases when locale is even available to check

},
{
describeLabel: 'NextResponse.next() -> getStaticProps page',
selector: 'NextResponse.next()#getStaticProps',
jsonPathMatcher: '/link/next-getstaticprops.json',
assertLocale: true,
},
{
describeLabel: 'NextResponse.next() -> fully static page',
Expand All @@ -78,11 +80,13 @@ test.describe('json data', () => {
describeLabel: 'NextResponse.rewrite() -> getServerSideProps page',
selector: 'NextResponse.rewrite()#getServerSideProps',
jsonPathMatcher: '/link/rewrite-me-getserversideprops.json',
assertLocale: true,
},
{
describeLabel: 'NextResponse.rewrite() -> getStaticProps page',
selector: 'NextResponse.rewrite()#getStaticProps',
jsonPathMatcher: '/link/rewrite-me-getstaticprops.json',
assertLocale: true,
},
]

Expand Down Expand Up @@ -144,10 +148,22 @@ test.describe('json data', () => {
test.describe('with 18n', () => {
for (const testConfig of testConfigs) {
test.describe(testConfig.describeLabel, () => {
for (const { localeLabel, pageWithLinksPathname } of [
{ localeLabel: 'implicit default locale', pageWithLinksPathname: '/link' },
{ localeLabel: 'explicit default locale', pageWithLinksPathname: '/en/link' },
{ localeLabel: 'explicit non-default locale', pageWithLinksPathname: '/fr/link' },
for (const { localeLabel, pageWithLinksPathname, expectedLocale } of [
{
localeLabel: 'implicit default locale',
pageWithLinksPathname: '/link',
expectedLocale: 'en',
},
{
localeLabel: 'explicit default locale',
pageWithLinksPathname: '/en/link',
expectedLocale: 'en',
},
{
localeLabel: 'explicit non-default locale',
pageWithLinksPathname: '/fr/link',
expectedLocale: 'fr',
},
]) {
test.describe(localeLabel, () => {
test('json data fetch', async ({ middlewareI18n, page }) => {
Expand Down Expand Up @@ -189,6 +205,10 @@ test.describe('json data', () => {

// we expect client navigation to work without browser reload
expect(browserNavigationWorked).toBe(true)

if (testConfig.assertLocale) {
await expect(page.getByTestId('current-locale')).toHaveText(expectedLocale)
}
})
})
}
Expand Down
11 changes: 6 additions & 5 deletions tests/fixtures/middleware-i18n/middleware.js
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Original file line number Diff line number Diff line change
@@ -1,5 +1,8 @@
import { NextResponse } from 'next/server'

/**
* @param {import('next/server').NextRequest} request
*/
export async function middleware(request) {
const url = request.nextUrl

Expand All @@ -17,11 +20,9 @@ export async function middleware(request) {
}

if (url.pathname.startsWith('/link/rewrite-me')) {
const rewriteUrl = new URL(
url.pathname.replace('/link/rewrite-me', '/link/rewrite-target'),
url,
)
return NextResponse.rewrite(rewriteUrl, {
// use NextUrl to rewrite the URL as it does preserve the locale
url.pathname = url.pathname.replace('/link/rewrite-me', '/link/rewrite-target')
return NextResponse.rewrite(url, {
Comment on lines -20 to +25
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Note: previous rewrite was just losing locale url due to using just NextURL.pathname to construct new URL effectively losing locale context in the process.

This change keeps using NextURL and just mutate pathname portion of it which preserve locale context and resulting in seemingly working as expected rewrites

headers: {
'x-middleware-test': 'link-rewrite',
},
Expand Down
15 changes: 12 additions & 3 deletions tests/fixtures/middleware-i18n/pages/link/next-getserversideprops.js
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Original file line number Diff line number Diff line change
@@ -1,15 +1,24 @@
export default function Page() {
export default function Page({ locale, locales }) {
return (
<div data-page="NextResponse.next()#getServerSideProps">
<h1>
<code>getServerSideProps</code> page
</h1>
<dt>Current locale:</dt>
<dd data-testid="current-locale">{locale ?? 'N/A'}</dd>
<dt>All locales:</dt>
<dd data-testid="all-locales">{locales ? locales.join(',') : 'N/A'}</dd>
</div>
)
}

export function getServerSideProps() {
/** @type {import('next').GetServerSideProps} */
export function getServerSideProps({ locale, locales }) {
console.log('NextResponse.next()#getServerSideProps', { locale, locales })
return {
props: {},
props: {
locale,
locales,
},
}
}
16 changes: 13 additions & 3 deletions tests/fixtures/middleware-i18n/pages/link/next-getstaticprops.js
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Original file line number Diff line number Diff line change
@@ -1,15 +1,25 @@
export default function Page() {
export default function Page({ locale, locales }) {
return (
<div data-page="NextResponse.next()#getStaticProps">
<h1>
<code>getStaticProps</code> page
</h1>
<dt>Current locale:</dt>
<dd data-testid="current-locale">{locale ?? 'N/A'}</dd>
<dt>All locales:</dt>
<dd data-testid="all-locales">{locales ? locales.join(',') : 'N/A'}</dd>
</div>
)
}

export function getStaticProps() {
/** @type {import('next').GetStaticProps} */
export function getStaticProps({ locale, locales }) {
console.log('NextResponse.next()#getStaticProps', { locale, locales })
return {
props: {},
props: {
locale,
locales,
},
revalidate: 5,
}
}
15 changes: 12 additions & 3 deletions tests/fixtures/middleware-i18n/pages/link/rewrite-target-getserversideprops.js
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Original file line number Diff line number Diff line change
@@ -1,15 +1,24 @@
export default function Page() {
export default function Page({ locale, locales }) {
return (
<div data-page="NextResponse.rewrite()#getServerSideProps">
<h1>
<code>getServerSideProps</code> page
</h1>
<dt>Current locale:</dt>
<dd data-testid="current-locale">{locale ?? 'N/A'}</dd>
<dt>All locales:</dt>
<dd data-testid="all-locales">{locales ? locales.join(',') : 'N/A'}</dd>
</div>
)
}

export function getServerSideProps() {
/** @type {import('next').GetServerSideProps} */
export function getServerSideProps({ locale, locales }) {
console.log('NextResponse.rewrite()#getServerSideProps', { locale, locales })
return {
props: {},
props: {
locale,
locales,
},
}
}
16 changes: 13 additions & 3 deletions tests/fixtures/middleware-i18n/pages/link/rewrite-target-getstaticprops.js
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Original file line number Diff line number Diff line change
@@ -1,15 +1,25 @@
export default function Page() {
export default function Page({ locale, locales }) {
return (
<div data-page="NextResponse.rewrite()#getStaticProps">
<h1>
<code>getStaticProps</code> page
</h1>
<dt>Current locale:</dt>
<dd data-testid="current-locale">{locale ?? 'N/A'}</dd>
<dt>All locales:</dt>
<dd data-testid="all-locales">{locales ? locales.join(',') : 'N/A'}</dd>
</div>
)
}

export function getStaticProps() {
/** @type {import('next').GetStaticProps} */
export function getStaticProps({ locale, locales }) {
console.log('NextResponse.rewrite()#getStaticProps', { locale, locales })
return {
props: {},
props: {
locale,
locales,
},
revalidate: 5,
}
}
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