Fix broken clone method for classification metrics (#1250)

* fix clone method
* chlog

Co-authored-by: Jirka <[email protected]>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: 3 people

CHANGELOG.md

@@ -16,22 +16,22 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
-- 
+-
 
 
 ### Deprecated
 
-- 
+-
 
 
 ### Removed
 
-- 
+-
 
 
 ### Fixed
 
-- 
+- Fixed broken clone method for classification metrics ([#1250](https://github.com/Lightning-AI/metrics/pull/1250))
 
 
 ## [0.10.0] - 2022-10-04

src/torchmetrics/metric.py

@@ -16,7 +16,7 @@
 from abc import ABC, abstractmethod
 from contextlib import contextmanager
 from copy import deepcopy
-from typing import Any, Callable, Dict, Generator, List, Optional, Sequence, Union
+from typing import Any, Callable, Dict, Generator, List, Optional, Sequence, Tuple, Union
 
 import torch
 from torch import Tensor
@@ -848,6 +848,9 @@ def __pos__(self) -> "Metric":
     def __getitem__(self, idx: int) -> "Metric":
         return CompositionalMetric(lambda x: x[idx], self, None)
 
+    def __getnewargs__(self) -> Tuple:
+        return (Metric.__str__(self),)
+
 
 def _neg(x: Tensor) -> Tensor:
     return -torch.abs(x)

tests/unittests/helpers/testers.py

@@ -165,6 +165,11 @@ def _class_test(
     if check_scriptable:
         torch.jit.script(metric)
 
+    # check that metric can be cloned
+    clone = metric.clone()
+    assert clone is not metric, "Clone is not a different object than the metric"
+    assert type(clone) == type(metric), "Type of clone did not match metric type"
+
     # move to device
     metric = metric.to(device)
     preds = apply_to_collection(preds, Tensor, lambda x: x.to(device))