Add message about ckpt_path hyperparameters when parsing fails

Author: mauvilsa

src/lightning/pytorch/cli.py

@@ -564,7 +564,11 @@ def _parse_ckpt_path(self) -> None:
             hparams.pop("_instantiator", None)
             if hparams:
                 hparams = {self.config.subcommand: {"model": hparams}}
-                self.config = self.parser.parse_object(hparams, self.config)
+                try:
+                    self.config = self.parser.parse_object(hparams, self.config)
+                except SystemExit:
+                    sys.stderr.write("Parsing of ckpt_path hyperparameters failed!\n")
+                    raise
 
     def _dump_config(self) -> None:
         if hasattr(self, "config_dump"):

tests/tests_pytorch/test_cli.py

@@ -17,7 +17,7 @@
 import operator
 import os
 import sys
-from contextlib import ExitStack, contextmanager, redirect_stdout
+from contextlib import ExitStack, contextmanager, redirect_stderr, redirect_stdout
 from io import StringIO
 from pathlib import Path
 from typing import Callable, Optional, Union
@@ -520,6 +520,11 @@ def add_arguments_to_parser(self, parser):
     assert cli.config.predict.model.hidden_dim == 6
     assert cli.config_init.predict.model.layer.out_features == 3
 
+    err = StringIO()
+    with mock.patch("sys.argv", ["any.py"] + cli_args), redirect_stderr(err), pytest.raises(SystemExit):
+        cli = LightningCLI(BoringModel)
+    assert "Parsing of ckpt_path hyperparameters failed" in err.getvalue()
+
 
 def test_lightning_cli_submodules(cleandir):
     class MainModule(BoringModel):