fix(serveStatic): add guard to prevent reading empty folders (#3639)

Fixes  #3628

* fix(serveStatic): add guard to prevent reading empty folders

* fix(serveStatic): remove unnecessary Deno.stat

* test(serveStatic): add test cases related to isDir guard

runtime-tests/deno/middleware.test.tsx

@@ -139,6 +139,22 @@ Deno.test('Serve Static middleware', async () => {
   res = await app.request('http://localhost/static-absolute-root/plain.txt')
   assertEquals(res.status, 200)
   assertEquals(await res.text(), 'Deno!')
+
+  res = await app.request('http://localhost/static')
+  assertEquals(res.status, 404)
+  assertEquals(await res.text(), '404 Not Found')
+
+  res = await app.request('http://localhost/static/dir')
+  assertEquals(res.status, 404)
+  assertEquals(await res.text(), '404 Not Found')
+
+  res = await app.request('http://localhost/static/helloworld/nested')
+  assertEquals(res.status, 404)
+  assertEquals(await res.text(), '404 Not Found')
+
+  res = await app.request('http://localhost/static/helloworld/../')
+  assertEquals(res.status, 404)
+  assertEquals(await res.text(), '404 Not Found')
 })
 
 Deno.test('JWT Authentication middleware', async () => {

src/adapter/deno/serve-static.ts

@@ -10,6 +10,10 @@ export const serveStatic = <E extends Env = Env>(
   return async function serveStatic(c, next) {
     const getContent = async (path: string) => {
       try {
+        if (isDir(path)) {
+          return null
+        }
+
         const file = await open(path)
         return file.readable
       } catch (e) {
@@ -30,6 +34,7 @@ export const serveStatic = <E extends Env = Env>(
       } catch {}
       return isDir
     }
+
     return baseServeStatic({
       ...options,
       getContent,