Fix last checkpoint finding in filtered files with correct extension

src/lightning/pytorch/CHANGELOG.md

@@ -44,6 +44,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed checks for local file protocol due to fsspec changes in 2023.10.0 ([#19023](https://github.com/Lightning-AI/lightning/pull/19023))
 
 
+- Fixed automatic detection of 'last.ckpt' files to respect the extension when filtering ([#17072](https://github.com/Lightning-AI/lightning/pull/17072))
+
+
 
 ## [2.1.2] - 2023-11-15
 

src/lightning/pytorch/callbacks/model_checkpoint.py

@@ -631,6 +631,7 @@ def _find_last_checkpoints(self, trainer: "pl.Trainer") -> Set[str]:
                 os.path.normpath(p)
                 for p in self._fs.ls(ckpt_path, detail=False)
                 if self.CHECKPOINT_NAME_LAST in os.path.split(p)[1]
+                and os.path.split(p)[1].endswith(self.FILE_EXTENSION)
             }
         return set()
 

tests/tests_pytorch/checkpointing/test_model_checkpoint.py

@@ -1509,3 +1509,22 @@ def test_resume_and_old_checkpoint_files_remain(same_resume_folder, tmp_path):
     else:
         assert set(os.listdir(first)) == {"epoch=0-step=2.ckpt", "epoch=0-step=4.ckpt"}  # no files deleted
         assert set(os.listdir(second)) == {"epoch=0-step=6.ckpt", "epoch=0-step=8.ckpt"}
+
+
+@pytest.mark.parametrize(
+    "folder_contents,expected",
+    [
+        ([], []),
+        (["last"], []),
+        (["last", "last.ckpt"], ["last.ckpt"]),
+        (["log.txt", "last-v0.ckpt", "last-v1.ckpt"], ["last-v0.ckpt", "last-v1.ckpt"]),
+    ],
+)
+def test_find_last_checkpoints(folder_contents, expected, tmp_path):
+    for file in folder_contents:
+        (tmp_path / file).touch()
+
+    trainer = Trainer()
+    callback = ModelCheckpoint(dirpath=tmp_path)
+    files = callback._find_last_checkpoints(trainer)
+    assert files == {str(tmp_path / p) for p in expected}