Fix: pth files don't load on Windows (#1661)

* Don't treat zip path as OS path

* Add a test case

* Add code to generate test pth data

candle-core/src/pickle.rs

@@ -227,13 +227,11 @@ impl Object {
             _ => return Ok(None),
         };
         let (layout, dtype, file_path, storage_size) = rebuild_args(args)?;
-        let mut path = dir_name.to_path_buf();
-        path.push(file_path);
         Ok(Some(TensorInfo {
             name,
             dtype,
             layout,
-            path: path.to_string_lossy().into_owned(),
+            path: format!("{}/{}", dir_name.to_string_lossy(), file_path),
             storage_size,
         }))
     }

candle-core/tests/pth.py

@@ -0,0 +1,8 @@
+import torch
+from collections import OrderedDict
+
+# Write a trivial tensor to a pt file
+a= torch.tensor([[1,2,3,4], [5,6,7,8]])
+o = OrderedDict()
+o["test"] = a
+torch.save(o, "test.pt")

candle-core/tests/pth_tests.rs

@@ -0,0 +1,6 @@
+/// Regression test for pth files not loading on Windows.
+#[test]
+fn test_pth() {   
+    let tensors = candle_core::pickle::PthTensors::new("tests/test.pt").unwrap();
+    tensors.get("test").unwrap().unwrap();
+}