[CLI] Save only the configuration used (#11532)

Author: carmocca

CHANGELOG.md

@@ -8,7 +8,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ### Fixed
 
--
+- Fixed the format of the configuration saved automatically by the CLI's `SaveConfigCallback` ([#11532](https://github.com/PyTorchLightning/pytorch-lightning/pull/11532))
+
 
 -
 

tests/utilities/test_cli.py

@@ -1259,6 +1259,10 @@ def test_lightning_cli_config_before_subcommand():
     validate_mock.assert_called_once_with(cli.trainer, cli.model, verbose=False, ckpt_path="barfoo")
     assert cli.trainer.limit_val_batches == 1
 
+    save_config_callback = cli.trainer.callbacks[0]
+    assert save_config_callback.config["trainer"]["limit_val_batches"] == 1
+    assert save_config_callback.parser.subcommand == "validate"
+
 
 @RunIf(min_python="3.7.3")
 def test_lightning_cli_config_before_subcommand_two_configs():