fix(resolve-metadata): allow for search params in canonical URL (#65366)

When `alternates.canonical` is provided as a `URL` instance,
`searchParams` are discarded.
When canonical is provided as a string, the same search parameters work.
This behavior may be unintuitive.

#### Unexpected result (`foo=bar` is removed):
```ts
export const generateMetadata = () => {
	const canonical = new URL(`https://example.com/test?foo=bar`);

	return {
		alternates: { canonical: canonical },
	};
};
```

#### Works as expected:
```ts
export const generateMetadata = () => {
	const canonical = new URL(`https://example.com/test?foo=bar`);

	return {
		alternates: { canonical: canonical.toString() },
	};
};
```

Co-authored-by: Shu Ding <g@shud.in>
Co-authored-by: JJ Kasper <jj@jjsweb.site>

packages/next/src/lib/metadata/resolve-metadata.test.ts

@@ -626,6 +626,84 @@ describe('accumulateMetadata', () => {
       })
     })
 
+    it('should support string alternate canonical with search params', async () => {
+      const metadataItems: MetadataItems = [
+        [
+          {
+            alternates: {
+              canonical: 'https://localhost:3000/test?foo=bar',
+              languages: {
+                'en-US': 'https://example.com/en-US',
+                'de-DE': 'https://example.com/de-DE',
+              },
+              media: {
+                'only screen and (max-width: 600px)': '/mobile',
+              },
+              types: {
+                'application/rss+xml': 'https://example.com/rss',
+              },
+            },
+          },
+          null,
+        ],
+      ]
+      const metadata = await accumulateMetadata(metadataItems)
+      expect(metadata).toMatchObject({
+        alternates: {
+          canonical: { url: 'https://localhost:3000/test?foo=bar' },
+          languages: {
+            'en-US': [{ url: 'https://example.com/en-US' }],
+            'de-DE': [{ url: 'https://example.com/de-DE' }],
+          },
+          media: {
+            'only screen and (max-width: 600px)': [{ url: '/mobile' }],
+          },
+          types: {
+            'application/rss+xml': [{ url: 'https://example.com/rss' }],
+          },
+        },
+      })
+    })
+
+    it('should support URL alternate canonical with search params', async () => {
+      const metadataItems: MetadataItems = [
+        [
+          {
+            alternates: {
+              canonical: new URL('https://localhost:3000/test?foo=bar'),
+              languages: {
+                'en-US': 'https://example.com/en-US',
+                'de-DE': 'https://example.com/de-DE',
+              },
+              media: {
+                'only screen and (max-width: 600px)': '/mobile',
+              },
+              types: {
+                'application/rss+xml': 'https://example.com/rss',
+              },
+            },
+          },
+          null,
+        ],
+      ]
+      const metadata = await accumulateMetadata(metadataItems)
+      expect(metadata).toMatchObject({
+        alternates: {
+          canonical: { url: 'https://localhost:3000/test?foo=bar' },
+          languages: {
+            'en-US': [{ url: 'https://example.com/en-US' }],
+            'de-DE': [{ url: 'https://example.com/de-DE' }],
+          },
+          media: {
+            'only screen and (max-width: 600px)': [{ url: '/mobile' }],
+          },
+          types: {
+            'application/rss+xml': [{ url: 'https://example.com/rss' }],
+          },
+        },
+      })
+    })
+
     it('should support alternate descriptors', async () => {
       const metadataItems: MetadataItems = [
         [

packages/next/src/lib/metadata/resolvers/resolve-basics.ts

@@ -24,7 +24,11 @@ function resolveAlternateUrl(
   // If alter native url is an URL instance,
   // we treat it as a URL base and resolve with current pathname
   if (url instanceof URL) {
-    url = new URL(metadataContext.pathname, url)
+    const newUrl = new URL(metadataContext.pathname, url)
+    url.searchParams.forEach((value, key) =>
+      newUrl.searchParams.set(key, value)
+    )
+    url = newUrl
   }
   return resolveAbsoluteUrlWithPathname(url, metadataBase, metadataContext)
 }