Decide checkpoint phase-awareness from the checkpoint name only

tests/utils/test_checkpoint.py

@@ -258,6 +258,21 @@ def test_from_str(self) -> None:
                     metric_data=MetricData("eval_loss", 6.486097566010406e18),
                 ),
             ),
+            # phase-naive checkpoints under a dirpath that contains a phase
+            # marker are still phase-naive
+            (
+                "foo/eval_step_sweeps/epoch_2_step_1_acc=0.98",
+                CheckpointPath(
+                    "foo/eval_step_sweeps",
+                    epoch=2,
+                    step={Phase.NONE: 1},
+                    metric_data=MetricData("acc", 0.98),
+                ),
+            ),
+            (
+                "foo/train_step_dir/epoch_2_step_1",
+                CheckpointPath("foo/train_step_dir", epoch=2, step=1),
+            ),
         ]
         for path, expected_ckpt in valid_paths:
             parsed_ckpt = CheckpointPath.from_str(path)

torchtnt/utils/checkpoint.py

@@ -160,9 +160,13 @@ def _populate_from_str(self, checkpoint_path: str) -> None:
         Raises:
             ValueError: If the path is malformed (either non-parsable, or contains wrong data types)
         """
+        # Only the checkpoint name (the final path component) decides this. If we
+        # looked at the whole path, a dirpath that happens to contain
+        # "train_step"/"eval_step"/"predict_step" would flip a phase-naive
+        # checkpoint onto the phase-aware regex.
+        ckpt_name = checkpoint_path.rstrip("/").rsplit("/", 1)[-1]
         is_phase_aware = any(
-            phase in checkpoint_path
-            for phase in ["train_step", "eval_step", "predict_step"]
+            phase in ckpt_name for phase in ["train_step", "eval_step", "predict_step"]
         )
         regex = self.PHASE_AWARE_REGEX if is_phase_aware else self.PHASE_NAIVE_REGEX
         path_match = regex.match(checkpoint_path)