Load sub-configs from composite configs (#34410)

* save/load sub-configs

* nit forgot these

* fix copies

* move test to common

* use dict for sub-configs

* add load-save-laod test

* clean up modeling check

* oops this are correct keys

* fix some tests, missed some composite configs

* this model was missed

tests/test_configuration_common.py

@@ -17,12 +17,17 @@ import copy
 import json
 import os
 import tempfile
+from pathlib import Path
 
 from transformers import is_torch_available
+from transformers.utils import direct_transformers_import
 
 from .utils.test_configuration_utils import config_common_kwargs
 
 
+transformers_module = direct_transformers_import(Path(__file__).parent)
+
+
 class ConfigTester:
     def __init__(self, parent, config_class=None, has_text_modality=True, common_properties=None, **kwargs):
         self.parent = parent
@@ -35,9 +40,10 @@ class ConfigTester:
         config = self.config_class(**self.inputs_dict)
         common_properties = (
             ["hidden_size", "num_attention_heads", "num_hidden_layers"]
-            if self.common_properties is None
+            if self.common_properties is None and not self.config_class.sub_configs
             else self.common_properties
         )
+        common_properties = [] if common_properties is None else common_properties
 
         # Add common fields for text models
         if self.has_text_modality:
@@ -110,6 +116,44 @@ class ConfigTester:
 
         self.parent.assertEqual(config_second.to_dict(), config_first.to_dict())
 
+    def create_and_test_config_from_and_save_pretrained_composite(self):
+        """
+        Tests that composite or nested cofigs can be loaded and saved correctly. In case the config
+        has a sub-config, we should be able to call `sub_config.from_pretrained('general_config_file')`
+        and get a result same as if we loaded the whole config and obtained `config.sub_config` from it.
+        """
+        config = self.config_class(**self.inputs_dict)
+
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config.save_pretrained(tmpdirname)
+            general_config_loaded = self.config_class.from_pretrained(tmpdirname)
+            general_config_dict = config.to_dict()
+
+            # Iterate over all sub_configs if there are any and load them with their own classes
+            sub_configs = self.config_class.sub_configs
+            for sub_config_key, sub_class in sub_configs.items():
+                if sub_class.__name__ == "AutoConfig":
+                    sub_class = sub_class.for_model(**general_config_dict[sub_config_key]).__class__
+                    sub_config_loaded = sub_class.from_pretrained(tmpdirname)
+                else:
+                    sub_config_loaded = sub_class.from_pretrained(tmpdirname)
+
+                # Pop `transformers_version`, it never exists when a config is part of a general composite config
+                # Verify that loading with subconfig class results in same dict as if we loaded with general composite config class
+                sub_config_loaded_dict = sub_config_loaded.to_dict()
+                sub_config_loaded_dict.pop("transformers_version", None)
+                self.parent.assertEqual(sub_config_loaded_dict, general_config_dict[sub_config_key])
+
+                # Verify that the loaded config type is same as in the general config
+                type_from_general_config = type(getattr(general_config_loaded, sub_config_key))
+                self.parent.assertTrue(isinstance(sub_config_loaded, type_from_general_config))
+
+                # Now save only the sub-config and load it back to make sure the whole load-save-load pipeline works
+                with tempfile.TemporaryDirectory() as tmpdirname2:
+                    sub_config_loaded.save_pretrained(tmpdirname2)
+                    sub_config_loaded_2 = sub_class.from_pretrained(tmpdirname2)
+                    self.parent.assertEqual(sub_config_loaded.to_dict(), sub_config_loaded_2.to_dict())
+
     def create_and_test_config_with_num_labels(self):
         config = self.config_class(**self.inputs_dict, num_labels=5)
         self.parent.assertEqual(len(config.id2label), 5)
@@ -128,6 +172,9 @@ class ConfigTester:
             self.parent.assertIsNotNone(config)
 
     def check_config_arguments_init(self):
+        if self.config_class.sub_configs:
+            return  # TODO: @raushan composite models are not consistent in how they set general params
+
         kwargs = copy.deepcopy(config_common_kwargs)
         config = self.config_class(**kwargs)
         wrong_values = []
@@ -153,6 +200,7 @@ class ConfigTester:
         self.create_and_test_config_to_json_file()
         self.create_and_test_config_from_and_save_pretrained()
         self.create_and_test_config_from_and_save_pretrained_subfolder()
+        self.create_and_test_config_from_and_save_pretrained_composite()
         self.create_and_test_config_with_num_labels()
         self.check_config_can_be_init_without_params()
         self.check_config_arguments_init()