[Fix] Fix the logic of setting lazy_import

mmengine/config/config.py

@@ -421,11 +421,11 @@ def fromfile(filename: Union[str, Path],
             Config: Config instance built from config file.
         """
         filename = str(filename) if isinstance(filename, Path) else filename
-        if lazy_import is None:
-            lazy_import = Config._is_lazy_import(filename)
-        if not lazy_import:
+        inferred_lazy_import = Config._is_lazy_import(filename)
+        if not inferred_lazy_import or lazy_import is False:
             cfg_dict, cfg_text, env_variables = Config._file2dict(
-                filename, use_predefined_variables, use_environment_variables)
+                filename, use_predefined_variables, use_environment_variables,
+                lazy_import)
             if import_custom_modules and cfg_dict.get('custom_imports', None):
                 try:
                     import_modules_from_strings(**cfg_dict['custom_imports'])
@@ -794,18 +794,22 @@ def _substitute_base_vars(cfg: Any, base_var_dict: dict,
     def _file2dict(
             filename: str,
             use_predefined_variables: bool = True,
-            use_environment_variables: bool = True) -> Tuple[dict, str, dict]:
+            use_environment_variables: bool = True,
+            lazy_import: Optional[bool] = None) -> Tuple[dict, str, dict]:
         """Transform file to variables dictionary.
 
         Args:
             filename (str): Name of config file.
             use_predefined_variables (bool, optional): Whether to use
                 predefined variables. Defaults to True.
+            lazy_import (bool): Whether to load config in `lazy_import` mode.
+                If it is `None`, it will be deduced by the content of the
+                config file. Defaults to None.
 
         Returns:
             Tuple[dict, str]: Variables dictionary and text of Config.
         """
-        if Config._is_lazy_import(filename):
+        if lazy_import is None and Config._is_lazy_import(filename):
             raise RuntimeError(
                 'The configuration file type in the inheritance chain '
                 'must match the current configuration file type, either '
@@ -852,7 +856,9 @@ def _file2dict(
                     _cfg_dict, _cfg_text, _env_variables = Config._file2dict(
                         filename=base_cfg_path,
                         use_predefined_variables=use_predefined_variables,
-                        use_environment_variables=use_environment_variables)
+                        use_environment_variables=use_environment_variables,
+                        lazy_import=lazy_import,
+                    )
                     cfg_text_list.append(_cfg_text)
                     env_variables.update(_env_variables)
                     duplicate_keys = base_cfg_dict.keys() & _cfg_dict.keys()

tests/data/config/lazy_module_config/error_mix_using1.py

@@ -1,2 +1,2 @@
 # Copyright (c) OpenMMLab. All rights reserved.
-_base_ = './toy_model.py'
+_base_ = './error_mix_using3.py'

tests/data/config/lazy_module_config/error_mix_using3.py

@@ -0,0 +1,2 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+import numpy as np

tests/test_config/test_config.py

@@ -1030,6 +1030,12 @@ def _compare_dict(a, b):
                 osp.join(self.data_path,
                          'config/lazy_module_config/error_mix_using1.py'))
 
+        # Force to import in non-lazy-import mode
+        Config.fromfile(
+            osp.join(self.data_path,
+                     'config/lazy_module_config/error_mix_using1.py'),
+            lazy_import=False)
+
         # current lazy-import config, base text config
         with pytest.raises(RuntimeError, match='_base_ ='):
             Config.fromfile(