Fixing problem for silently supporting jsonnet.

src/lightning/pytorch/cli.py

@@ -554,7 +554,9 @@ def parse_arguments(self, parser: LightningArgumentParser, args: ArgsType) -> No
     def _dump_config(self) -> None:
         if hasattr(self, "config_dump"):
             return
-        self.config_dump = yaml.safe_load(self.parser.dump(self.config, skip_link_targets=False, skip_none=False))
+        self.config_dump = yaml.safe_load(
+            self.parser.dump(self.config, skip_link_targets=False, skip_none=False, format="yaml")
+        )
         if "subcommand" in self.config:
             self.config_dump = self.config_dump[self.config.subcommand]
 

tests/tests_pytorch/test_cli.py

@@ -1858,3 +1858,23 @@ def test_lightning_cli_with_args_given(args):
 def test_lightning_cli_args_and_sys_argv_warning():
     with mock.patch("sys.argv", ["", "--model.foo=456"]), pytest.warns(Warning, match="LightningCLI's args parameter "):
         LightningCLI(TestModel, run=False, args=["--model.foo=789"])
+
+
+def test_lightning_cli_jsonnet(cleandir):
+    class MainModule(BoringModel):
+        def __init__(self, main_param: int = 1):
+            super().__init__()
+
+    config = """{
+        "model":{
+            "main_param": 2
+        }
+    }"""
+    config_path = Path("config.jsonnet")
+    config_path.write_text(config)
+
+    cli_args = [f"--config={config_path}"]
+    with mock.patch("sys.argv", ["any.py"] + cli_args):
+        cli = LightningCLI(MainModule, run=False, parser_kwargs={"parser_mode": "jsonnet"})
+
+    assert cli.config["model"]["main_param"] == 2