fix(http): handle HEAD requests in serveFile (#6218)

http/file_server.ts

@@ -179,7 +179,7 @@ export async function serveFile(
   filePath: string,
   options?: ServeFileOptions,
 ): Promise<Response> {
-  if (req.method !== METHOD.Get) {
+  if (req.method !== METHOD.Get && req.method !== METHOD.Head) {
     return createStandardResponse(STATUS_CODE.MethodNotAllowed);
   }
 
@@ -220,6 +220,25 @@ export async function serveFile(
     headers.set(HEADER.ETag, etag);
   }
 
+  // Set mime-type using the file extension in filePath
+  const contentTypeValue = contentType(extname(filePath));
+  if (contentTypeValue) {
+    headers.set(HEADER.ContentType, contentTypeValue);
+  }
+  const fileSize = fileInfo.size;
+
+  if (req.method === METHOD.Head) {
+    // Set content length
+    headers.set(HEADER.ContentLength, `${fileSize}`);
+
+    const status = STATUS_CODE.OK;
+    return new Response(null, {
+      status,
+      statusText: STATUS_TEXT[status],
+      headers,
+    });
+  }
+
   if (etag || fileInfo.mtime) {
     // If a `if-none-match` header is present and the value matches the tag or
     // if a `if-modified-since` header is present and the value is bigger than
@@ -243,14 +262,6 @@ export async function serveFile(
     }
   }
 
-  // Set mime-type using the file extension in filePath
-  const contentTypeValue = contentType(extname(filePath));
-  if (contentTypeValue) {
-    headers.set(HEADER.ContentType, contentTypeValue);
-  }
-
-  const fileSize = fileInfo.size;
-
   const rangeValue = req.headers.get(HEADER.Range);
 
   // handle range request

http/file_server_test.ts

@@ -1137,3 +1137,15 @@ async function readUntilMatch(
   reader.releaseLock();
   return dec.decode(buf);
 }
+
+Deno.test(async function serveFileHeadRequest() {
+  const req = new Request("http://localhost/testdata/test_file.txt", {
+    method: "HEAD",
+  });
+  const res = await serveFile(req, TEST_FILE_PATH);
+  assert(!res.body);
+  assertEquals(res.status, 200);
+  assertEquals(res.statusText, "OK");
+  assertEquals(res.headers.get("content-type"), "text/plain; charset=UTF-8");
+  assertEquals(res.headers.get("content-length"), "10034");
+});