From dab7dae8f2ccf1c0d46b67323a27369aa9f8f719 Mon Sep 17 00:00:00 2001
From: Jan Amann <jan@amann.me>
Date: Tue, 17 Sep 2024 10:54:00 +0200
Subject: [PATCH 1/2] fix: Handle overlapping locale prefixes correctly

---
 .../next-intl/src/middleware/utils.test.tsx   | 20 +++++++++++++++++++
 packages/next-intl/src/middleware/utils.tsx   |  3 +++
 2 files changed, 23 insertions(+)

diff --git a/packages/next-intl/src/middleware/utils.test.tsx b/packages/next-intl/src/middleware/utils.test.tsx
index e2609114b..17b3afb33 100644
--- a/packages/next-intl/src/middleware/utils.test.tsx
+++ b/packages/next-intl/src/middleware/utils.test.tsx
@@ -3,6 +3,7 @@ import {
   formatPathnameTemplate,
   getInternalTemplate,
   getNormalizedPathname,
+  getPathnameMatch,
   getRouteParams
 } from './utils';
 
@@ -168,3 +169,22 @@ describe('getInternalTemplate', () => {
     ]);
   });
 });
+
+describe('getPathnameMatch', () => {
+  it('prioritizes more specific prefixes for overlapping locales', () => {
+    expect(
+      getPathnameMatch('/de/at/test', ['de', 'de-at'], {
+        mode: 'always',
+        prefixes: {
+          'de-at': '/de/at',
+          de: '/de'
+        }
+      })
+    ).toEqual({
+      locale: 'de-at',
+      prefix: '/de/at',
+      exact: true,
+      matchedPrefix: '/de/at'
+    });
+  });
+});
diff --git a/packages/next-intl/src/middleware/utils.tsx b/packages/next-intl/src/middleware/utils.tsx
index 26fda1b75..d70468166 100644
--- a/packages/next-intl/src/middleware/utils.tsx
+++ b/packages/next-intl/src/middleware/utils.tsx
@@ -151,6 +151,9 @@ export function getPathnameMatch<AppLocales extends Locales>(
   | undefined {
   const localePrefixes = getLocalePrefixes(locales, localePrefix);
 
+  // More specific ones first
+  localePrefixes.sort((a, b) => b[1].length - a[1].length);
+
   for (const [locale, prefix] of localePrefixes) {
     let exact, matches;
     if (pathname === prefix || pathname.startsWith(prefix + '/')) {

From 7fe99075355c1502c5ebbe3c6ff2dc46874751a2 Mon Sep 17 00:00:00 2001
From: Jan Amann <jan@amann.me>
Date: Tue, 17 Sep 2024 11:10:28 +0200
Subject: [PATCH 2/2] More tests

---
 .../next-intl/src/middleware/utils.test.tsx   | 34 +++++++++++++------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/packages/next-intl/src/middleware/utils.test.tsx b/packages/next-intl/src/middleware/utils.test.tsx
index 17b3afb33..e322b5538 100644
--- a/packages/next-intl/src/middleware/utils.test.tsx
+++ b/packages/next-intl/src/middleware/utils.test.tsx
@@ -171,20 +171,34 @@ describe('getInternalTemplate', () => {
 });
 
 describe('getPathnameMatch', () => {
-  it('prioritizes more specific prefixes for overlapping locales', () => {
-    expect(
-      getPathnameMatch('/de/at/test', ['de', 'de-at'], {
-        mode: 'always',
-        prefixes: {
-          'de-at': '/de/at',
-          de: '/de'
-        }
-      })
-    ).toEqual({
+  it('prioritizes more specific custom prefixes for overlapping ones', () => {
+    const locales = ['de', 'de-at', 'de-at-x-test'] as const;
+    const localePrefix = {
+      mode: 'always',
+      prefixes: {
+        de: '/de',
+        'de-at': '/de/at',
+        // Longer locale, shorter prefix
+        'de-at-x-test': '/de/a'
+      }
+    } as const;
+
+    expect(getPathnameMatch('/de/at/test', locales, localePrefix)).toEqual({
       locale: 'de-at',
       prefix: '/de/at',
       exact: true,
       matchedPrefix: '/de/at'
     });
   });
+
+  it('does not confuse unrelated parts of the pathname with a locale', () => {
+    expect(
+      getPathnameMatch('/de/ats', ['de', 'de-at'], {mode: 'always'})
+    ).toEqual({
+      locale: 'de',
+      prefix: '/de',
+      exact: true,
+      matchedPrefix: '/de'
+    });
+  });
 });