test: fix load-custom-routes test

Author: Netail

packages/next/src/lib/load-custom-routes.test.ts

@@ -144,12 +144,25 @@ describe('loadCustomRoutes', () => {
 
       it('does not insert assetPrefix rewrite for /_next/ paths when assetPrefix is absolute URL', async () => {
         const customRoutes = await loadCustomRoutes({
-          assetPrefix: 'https://example.com/custom-asset-prefix',
+          assetPrefix: 'https://example.com',
         })
         expect(customRoutes.rewrites.beforeFiles).toEqual([])
         expect(customRoutes.rewrites.afterFiles).toEqual([])
       })
 
+      it('automatically insert assetPrefix rewrite for /_next/ paths when assetPrefix is absolute URL with a path', async () => {
+        const customRoutes = await loadCustomRoutes({
+          assetPrefix: 'https://example.com/custom-asset-prefix',
+        })
+        expect(customRoutes.rewrites.beforeFiles).toEqual([
+          {
+            destination: '/_next/:path+',
+            source: '/custom-asset-prefix/_next/:path+',
+          },
+        ])
+        expect(customRoutes.rewrites.afterFiles).toEqual([])
+      })
+
       it('does not add rewrite when assetPrefix === basePath', async () => {
         const customRoutes = await loadCustomRoutes({
           assetPrefix: '/base',

packages/next/src/lib/load-custom-routes.ts

@@ -608,14 +608,16 @@ async function loadRewrites(config: NextConfig) {
       prefix = new URL(config.assetPrefix).pathname
     }
 
-    const assetPrefix = prefix.startsWith('/') ? prefix : `/${prefix}`
-    const basePath = config.basePath || ''
-    // If these are the same, then this would result in an infinite rewrite.
-    if (assetPrefix !== basePath) {
-      maybeAssetPrefixRewrite.push({
-        source: `${assetPrefix}/_next/:path+`,
-        destination: `${basePath}/_next/:path+`,
-      })
+    if (prefix && prefix !== '/') {
+      const assetPrefix = prefix.startsWith('/') ? prefix : `/${prefix}`
+      const basePath = config.basePath || ''
+      // If these are the same, then this would result in an infinite rewrite.
+      if (assetPrefix !== basePath) {
+        maybeAssetPrefixRewrite.push({
+          source: `${assetPrefix}/_next/:path+`,
+          destination: `${basePath}/_next/:path+`,
+        })
+      }
     }
   }