Implemented test for cli

It shows the inconsitency that is required to cli arguments depending on how you set up the model and data module

Author: MrWhatZitToYaa

tests/tests_pytorch/test_cli.py

@@ -597,42 +597,47 @@ def add_arguments_to_parser(self, parser):
     assert cli.model.num_classes == 5
 
 
+# Notes:
+# - if variable is class attribute, it will only be present after instantiation -> apply_on="instantiate"
+# If you link argumetns and then try to pass them additionally, it will raise an error
+
+
 def test_lightning_cli_link_arguments_init():
     # Will not work without init_args ("--data.init_args.batch_size=12")
     class MyLightningCLI(LightningCLI):
         def add_arguments_to_parser(self, parser):
-            parser.link_arguments("data.batch_size", "model.init_args.batch_size")
+            parser.link_arguments("data.batch_size", "model.batch_size")
+            parser.link_arguments("data.num_classes", "model.num_classes", apply_on="instantiate")
 
     cli_args = [
-        "--data=tests_pytorch.test_cli.BoringDataModuleBatchSizeAndClasses",
-        "--model=tests_pytorch.test_cli.BoringModelRequiredClasses",
-        "--data.init_args.batch_size=12",
-        "--model.init_args.num_classes=5",
+        "--data.batch_size=12",
     ]
 
     with mock.patch("sys.argv", ["any.py"] + cli_args):
-        cli = MyLightningCLI(run=False)
+        cli = MyLightningCLI(BoringModelRequiredClasses, BoringDataModuleBatchSizeAndClasses, run=False)
 
+    assert cli.model.batch_size == 12
     assert cli.datamodule.batch_size == 12
+    assert cli.model.num_classes == 5
+    assert cli.datamodule.num_classes == 5
 
     # Will work without init_args ("--data.batch_size=12")
     class MyLightningCLI(LightningCLI):
         def add_arguments_to_parser(self, parser):
-            pass
+            parser.link_arguments("data.batch_size", "model.batch_size")
+            parser.link_arguments("data.num_classes", "model.num_classes", apply_on="instantiate")
 
     cli_args = [
         "--data=tests_pytorch.test_cli.BoringDataModuleBatchSizeAndClasses",
         "--model=tests_pytorch.test_cli.BoringModelRequiredClasses",
         "--data.batch_size=12",
-        "--model.num_classes=12",
     ]
 
     with mock.patch("sys.argv", ["any.py"] + cli_args):
         cli = MyLightningCLI(run=False)
 
-    print(cli.config)
-
     assert cli.datamodule.batch_size == 12
+    assert cli.model.batch_size == 12
 
 
 class EarlyExitTestModel(BoringModel):