Allow list index keys in Config.merge_from_dict (#696)

* Allow list keys in Config merge from dict

* Reformat

* Set allow_list_keys default as True in merge_from_dict

* Fix docstring

* fix a small typo

mmcv/fileio/file_client.py

 import inspect
-import warnings
 from abc import ABCMeta, abstractmethod
 
 
@@ -32,7 +31,6 @@ class CephBackend(BaseStorageBackend):
     def __init__(self, path_mapping=None):
         try:
             import ceph
-            warnings.warn('Ceph is deprecate in favor of Petrel.')
         except ImportError:
             raise ImportError('Please install ceph to enable CephBackend.')
 

mmcv/utils/config.py

@@ -190,20 +190,55 @@ class Config:
         return cfg_dict, cfg_text
 
     @staticmethod
-    def _merge_a_into_b(a, b):
-        # merge dict `a` into dict `b` (non-inplace). values in `a` will
-        # overwrite `b`.
-        # copy first to avoid inplace modification
+    def _merge_a_into_b(a, b, allow_list_keys=False):
+        """merge dict ``a`` into dict ``b`` (non-inplace).
+
+        Values in ``a`` will overwrite ``b``. ``b`` is copied first to avoid
+        in-place modifications.
+
+        Args:
+            a (dict): The source dict to be merged into ``b``.
+            b (dict): The origin dict to be fetch keys from ``a``.
+            allow_list_keys (bool): If True, int string keys (e.g. '0', '1')
+              are allowed in source ``a`` and will replace the element of the
+              corresponding index in b if b is a list. Default: False.
+
+        Returns:
+            dict: The modified dict of ``b`` using ``a``.
+
+        Examples:
+            # Normally merge a into b.
+            >>> Config._merge_a_into_b(
+            ...     dict(obj=dict(a=2)), dict(obj=dict(a=1)))
+            {'obj': {'a': 2}}
+
+            # Delete b first and merge a into b.
+            >>> Config._merge_a_into_b(
+            ...     dict(obj=dict(_delete_=True, a=2)), dict(obj=dict(a=1)))
+            {'obj': {'a': 2}}
+
+            # b is a list
+            >>> Config._merge_a_into_b(
+            ...     {'0': dict(a=2)}, [dict(a=1), dict(b=2)], True)
+            [{'a': 2}, {'b': 2}]
+        """
         b = b.copy()
         for k, v in a.items():
-            if isinstance(v, dict) and k in b and not v.pop(DELETE_KEY, False):
-                if not isinstance(b[k], dict):
+            if allow_list_keys and k.isdigit() and isinstance(b, list):
+                k = int(k)
+                if len(b) <= k:
+                    raise KeyError(f'Index {k} exceeds the length of list {b}')
+                b[k] = Config._merge_a_into_b(v, b[k], allow_list_keys)
+            elif isinstance(v,
+                            dict) and k in b and not v.pop(DELETE_KEY, False):
+                allowed_types = (dict, list) if allow_list_keys else dict
+                if not isinstance(b[k], allowed_types):
                     raise TypeError(
                         f'{k}={v} in child config cannot inherit from base '
                         f'because {k} is a dict in the child config but is of '
                         f'type {type(b[k])} in base config. You may set '
                         f'`{DELETE_KEY}=True` to ignore the base config')
-                b[k] = Config._merge_a_into_b(v, b[k])
+                b[k] = Config._merge_a_into_b(v, b[k], allow_list_keys)
             else:
                 b[k] = v
         return b
@@ -403,7 +438,7 @@ class Config:
             else:
                 mmcv.dump(cfg_dict, file)
 
-    def merge_from_dict(self, options):
+    def merge_from_dict(self, options, allow_list_keys=True):
         """Merge list into cfg_dict.
 
         Merge the dict parsed by MultipleKVAction into this cfg.
@@ -417,8 +452,21 @@ class Config:
             >>> assert cfg_dict == dict(
             ...     model=dict(backbone=dict(depth=50, with_cp=True)))
 
+            # Merge list element
+            >>> cfg = Config(dict(pipeline=[
+            ...     dict(type='LoadImage'), dict(type='LoadAnnotations')]))
+            >>> options = dict(pipeline={'0': dict(type='SelfLoadImage')})
+            >>> cfg.merge_from_dict(options, allow_list_keys=True)
+            >>> cfg_dict = super(Config, self).__getattribute__('_cfg_dict')
+            >>> assert cfg_dict == dict(pipeline=[
+            ...     dict(type='SelfLoadImage'), dict(type='LoadAnnotations')])
+
         Args:
             options (dict): dict of configs to merge from.
+            allow_list_keys (bool): If True, int string keys (e.g. '0', '1')
+              are allowed in ``options`` and will replace the element of the
+              corresponding index in the config if the config is a list.
+              Default: True.
         """
         option_cfg_dict = {}
         for full_key, v in options.items():
@@ -432,7 +480,9 @@ class Config:
 
         cfg_dict = super(Config, self).__getattribute__('_cfg_dict')
         super(Config, self).__setattr__(
-            '_cfg_dict', Config._merge_a_into_b(option_cfg_dict, cfg_dict))
+            '_cfg_dict',
+            Config._merge_a_into_b(
+                option_cfg_dict, cfg_dict, allow_list_keys=allow_list_keys))
 
 
 class DictAction(Action):

tests/data/config/s.py

+item = [{'a': 0}, {'b': 0, 'c': 0}]

tests/test_fileclient.py

@@ -70,9 +70,6 @@ class TestFileClient:
 
     @patch('ceph.S3Client', MockS3Client)
     def test_ceph_backend(self):
-        with pytest.warns(
-                Warning, match='Ceph is deprecate in favor of Petrel.'):
-            FileClient('ceph')
         ceph_backend = FileClient('ceph')
 
         # input path is Path object

tests/test_utils/test_config.py

@@ -219,6 +219,24 @@ def test_merge_from_dict():
     assert cfg.item2 == dict(a=1, b=0.1)
     assert cfg.item3 is False
 
+    cfg_file = osp.join(data_path, 'config/s.py')
+    cfg = Config.fromfile(cfg_file)
+
+    # Allow list keys
+    input_options = {'item.0.a': 1, 'item.1.b': 1}
+    cfg.merge_from_dict(input_options, allow_list_keys=True)
+    assert cfg.item == [{'a': 1}, {'b': 1, 'c': 0}]
+
+    # allow_list_keys is False
+    input_options = {'item.0.a': 1, 'item.1.b': 1}
+    with pytest.raises(TypeError):
+        cfg.merge_from_dict(input_options, allow_list_keys=False)
+
+    # Overflowed index number
+    input_options = {'item.2.a': 1}
+    with pytest.raises(KeyError):
+        cfg.merge_from_dict(input_options, allow_list_keys=True)
+
 
 def test_merge_delete():
     cfg_file = osp.join(data_path, 'config/delete.py')