add deprecation warning for deprecated modules (#1277)

* add deprecation warning for deprecated modules

* fix deprecation warning

* fix formatting

* remove unused var

torchdata/__init__.py

@@ -32,3 +32,23 @@ def __getattr__(name):
                 return globals()[name]
             else:
                 raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+
+_warning_shown = False
+
+
+def deprecation_warning():
+    global _warning_shown
+    if not _warning_shown:
+        _warning_shown = True
+        import warnings
+
+        warnings.warn(
+            "\n################################################################################\n"
+            "WARNING!\n"
+            "The 'datapipes', 'dataloader2' modules are deprecated and will be removed in a\n"
+            "future torchdata release! Please see https://github.com/pytorch/data/issues/1196\n"
+            "to learn more and leave feedback.\n"
+            "################################################################################\n",
+            stacklevel=2,
+        )

torchdata/dataloader2/__init__.py

@@ -34,3 +34,8 @@
 ]
 
 assert __all__ == sorted(__all__)
+
+
+from torchdata import deprecation_warning
+
+deprecation_warning()

torchdata/datapipes/__init__.py

@@ -11,3 +11,8 @@
 from . import iter, map, utils
 
 __all__ = ["DataChunk", "functional_datapipe", "iter", "map", "utils"]
+
+
+from torchdata import deprecation_warning
+
+deprecation_warning()