Test for cache extraction to /dev/fd/{n}

Author: myzhang1029

src/cache/cache.rs

@@ -867,4 +867,38 @@ mod test {
         let result = runtime.block_on(cache_read.extract_objects(objects, pool));
         assert!(result.is_ok(), "Extracting to /dev/null should succeed");
     }
+
+    #[cfg(unix)]
+    #[test]
+    fn test_extract_object_to_dev_fd_something() {
+        // Open a pipe, write to `/dev/fd/{fd}` and check the other end that the correct data was written.
+        use std::os::fd::AsRawFd;
+        use tokio::io::AsyncReadExt;
+        let runtime = tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .worker_threads(1)
+            .build()
+            .unwrap();
+        let pool = runtime.handle();
+        let mut cache_data = CacheWrite::new();
+        let data = b"test data";
+        cache_data.put_bytes("test_key", data).unwrap();
+        let cache_read = CacheRead::from(io::Cursor::new(cache_data.finish().unwrap())).unwrap();
+        runtime.block_on(async {
+            let (sender, mut receiver) = tokio::net::unix::pipe::pipe().unwrap();
+            let sender_fd = sender.into_blocking_fd().unwrap();
+            let raw_fd = sender_fd.as_raw_fd();
+            let objects = vec![FileObjectSource {
+                key: "test_key".to_string(),
+                path: PathBuf::from(format!("/dev/fd/{}", raw_fd)),
+                optional: false,
+            }];
+            let result = cache_read.extract_objects(objects, pool).await;
+            assert!(result.is_ok(), "Extracting to /dev/fd/{} should succeed", raw_fd);
+            let mut buf = vec![0; data.len()];
+            let n = receiver.read_exact(&mut buf).await.unwrap();
+            assert_eq!(n, data.len(), "Read the correct number of bytes");
+            assert_eq!(buf, data, "Read the correct data from /dev/fd/{}", raw_fd);
+        });
+    }
 }