easier way to separate internal code from oss

Summary: Pull Request resolved: https://github.com/facebookresearch/d2go/pull/90

Reviewed By: zhanghang1989

Differential Revision: D29279123

fbshipit-source-id: d94cea65bd439d54fd14afded0dba066799cedca

d2go/data/__init__.py

 #!/usr/bin/env python3
 # Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
-
-
-import d2go.data.datasets

d2go/data/datasets.py

@@ -7,8 +7,8 @@ import importlib
 import logging
 import os
 
-from d2go.data.fb.adhoc_hive_dataset import COCOHiveLoaderConfig
 from d2go.utils.helper import get_dir_path
+from d2go.utils.misc import fb_overwritable
 from detectron2.data import DatasetCatalog, MetadataCatalog
 
 from .extended_coco import coco_text_load, extended_coco_load
@@ -48,11 +48,16 @@ def _register_extended_coco(dataset_name, split_dict):
     meta_data = split_dict.get("meta_data", {})
     MetadataCatalog.get(dataset_name).set(
         evaluator_type=evaluator_type,
-        auto_hive_loader_config=COCOHiveLoaderConfig,
         json_file=json_file,
         image_root=image_root,
-        **meta_data
+        **meta_data,
     )
+    _add_additional_extended_coco_metadata(dataset_name)
+
+
+@fb_overwritable()
+def _add_additional_extended_coco_metadata(dataset_name):
+    pass
 
 
 def _register_extended_lvis(dataset_name, split_dict):

d2go/utils/launch_environment.py

 #!/usr/bin/env python3
 # Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
+
+from d2go.utils.misc import fb_overwritable
+
+
+@fb_overwritable()
 def get_launch_environment():
     return "local"

d2go/utils/misc.py

@@ -12,6 +12,7 @@ import detectron2.utils.comm as comm
 import torch
 from d2go.config import CfgNode
 from detectron2.utils.file_io import PathManager
+from mobile_cv.common.misc.py import dynamic_import
 from tabulate import tabulate
 
 from .tensorboard_log_util import get_tensorboard_log_dir  # noqa: forwarding
@@ -104,9 +105,31 @@ def mode(net: torch.nn.Module, training: bool) -> Iterator[torch.nn.Module]:
     finally:
         net.train(istrain)
 
+
 def _log_api_usage(identifier: str):
     """
     Internal function used to log the usage of different d2go components
     inside facebook's infra.
     """
     torch._C._log_api_usage_once("d2go." + identifier)
+
+
+def fb_overwritable():
+    """Decorator on function that has alternative internal implementation"""
+    try:
+        import d2go.infra.fb  # NOQA
+
+        is_oss = False
+    except ImportError:
+        is_oss = True
+
+    def deco(oss_func):
+        if is_oss:
+            return oss_func
+        else:
+            oss_module = oss_func.__module__
+            fb_module = oss_module + "_fb"  # xxx.py -> xxx_fb.py
+            fb_func = dynamic_import("{}.{}".format(fb_module, oss_func.__name__))
+            return fb_func
+
+    return deco