[5.2.x] Fixed #36298 -- Truncated the overwritten file content in file_move_safe().

Regression in 58cd4902a71a3695dd6c21dc957f59c333db364c.

Thanks Baptiste Mispelon for the report.

Backport of 8ad3e80e88201f4c557f6fa79fcfc0f8a0961830 from main.

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/files/tests.py b/tests/files/tests.py
index 4f6d1fa74b..7e365aae39 100644
--- a/tests/files/tests.py
+++ b/tests/files/tests.py
@@ -496,6 +496,27 @@ class FileMoveSafeTests(unittest.TestCase):
             os.close(handle_b)
             os.close(handle_c)
 
+    def test_file_move_ensure_truncation(self):
+        with tempfile.NamedTemporaryFile(delete=False) as src:
+            src.write(b"content")
+            src_name = src.name
+        self.addCleanup(
+            lambda: os.remove(src_name) if os.path.exists(src_name) else None
+        )
+
+        with tempfile.NamedTemporaryFile(delete=False) as dest:
+            dest.write(b"This is a longer content.")
+            dest_name = dest.name
+        self.addCleanup(os.remove, dest_name)
+
+        with mock.patch("django.core.files.move.os.rename", side_effect=OSError()):
+            file_move_safe(src_name, dest_name, allow_overwrite=True)
+
+        with open(dest_name, "rb") as f:
+            content = f.read()
+
+        self.assertEqual(content, b"content")
+
 
 class SpooledTempTests(unittest.TestCase):
     def test_in_memory_spooled_temp(self):