Prevent append of trailing slash in cases where path ends with a file…

… extension

Canonical URLs specified in the metadata object are being resolved
incorrectly when the trailing slash config is set to true.  In cases
where the path ends with something like `.html` it will append the slash
resulting in `.html/` which causes issues for SEO.  This will validate
that if the path has an extension, no slash will be appended.

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

@@ -110,6 +110,13 @@ describe('resolveAbsoluteUrlWithPathname', () => {
         'https://example.com/foo?bar'
       )
     })
+
+    it('should not add trailing slash to relative url that ends with a file extension', () => {
+      expect(resolver('/foo.html')).toBe('https://example.com/foo.html')
+      expect(resolver(new URL('/foo.html', metadataBase))).toBe(
+        'https://example.com/foo.html'
+      )
+    })
   })
 })
 

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

@@ -112,6 +112,8 @@ function resolveAbsoluteUrlWithPathname(
     let isRelative = resolvedUrl.startsWith('/')
     let isExternal = false
     let hasQuery = resolvedUrl.includes('?')
+    let hasFileExtension = /\.[0-9a-z]+$/i.test(resolvedUrl)
+
     if (!isRelative) {
       try {
         const parsedUrl = new URL(resolvedUrl)
@@ -121,7 +123,8 @@ function resolveAbsoluteUrlWithPathname(
         // If it's not a valid URL, treat it as external
         isExternal = true
       }
-      if (!isExternal && !hasQuery) return `${resolvedUrl}/`
+      if (!hasFileExtension && !isExternal && !hasQuery)
+        return `${resolvedUrl}/`
     }
   }