From 4cc60645dd7464b12eaf98f49db1058becb746ec Mon Sep 17 00:00:00 2001
From: Fabien Hertschuh <1091026+hertschuh@users.noreply.github.com>
Date: Mon, 29 Apr 2024 12:14:18 -0700
Subject: [PATCH] Return a tuple from `ops.shape` with the Torch backend.

With Torch, `x.shape` returns a `torch.Size`, which is a subclass of `tuple` but can cause different behaviors. In particular `convert_to_tensor` does not work on `torch.Size`.

This fixes https://github.com/keras-team/keras/issues/18900
---
 keras/src/backend/torch/core.py | 3 ++-
 keras/src/ops/core_test.py      | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/keras/src/backend/torch/core.py b/keras/src/backend/torch/core.py
index 8cc6c5b5b56..68453255b1f 100644
--- a/keras/src/backend/torch/core.py
+++ b/keras/src/backend/torch/core.py
@@ -234,7 +234,8 @@ def is_tensor(x):
 
 
 def shape(x):
-    return x.shape
+    # Convert from `torch.Size` to plain tuple.
+    return tuple(x.shape)
 
 
 def cast(x, dtype):
diff --git a/keras/src/ops/core_test.py b/keras/src/ops/core_test.py
index 31d553853b6..29526c20ad4 100644
--- a/keras/src/ops/core_test.py
+++ b/keras/src/ops/core_test.py
@@ -338,10 +338,12 @@ def test_stop_gradient_return(self):
         self.assertAllClose(x, y)
 
     def test_shape(self):
-        x = np.ones((2, 3, 7, 1))
+        x = ops.ones((2, 3, 7, 1))
+        self.assertEqual(core.shape(x).__class__, tuple)
         self.assertAllEqual(core.shape(x), (2, 3, 7, 1))
 
         x = KerasTensor((None, 3, None, 1))
+        self.assertEqual(core.shape(x).__class__, tuple)
         self.assertAllEqual(core.shape(x), (None, 3, None, 1))
 
     @pytest.mark.skipif(