Raise warning for unpickable local function

Summary:
Fixes #538
- Improve the validation function to raise warning about unpickable function when either lambda or local function is provided to DataPipe.
- The inner function from functools.partial object is extracted as well for validation
- Mimic the behavior of pickle module for local lambda function: It would only raise Error for the local function rather than lambda function. So, we will raise warning about local function not lambda function.
```py

>>> import pickle
>>> def fn():
...     lf = lambda x: x
...     pickle.dumps(lf)
>>> pickle.dumps(fn)
AttributeError: Can't pickle local object 'fn.<locals>.<lambda>'
```

This Diff also fixes the Error introduced by pytorch/pytorch#79344

Differential Revision: D37417556

fbshipit-source-id: cf1df990b7ba9278d7eb9b62162edf3d573927ff

torchdata/datapipes/iter/transform/callable.py

@@ -7,7 +7,7 @@
 from typing import Callable, Iterator, List, TypeVar
 
 from torch.utils.data import functional_datapipe, IterDataPipe
-from torch.utils.data.datapipes.utils.common import _check_lambda_fn
+from torch.utils.data.datapipes.utils.common import _check_unpickable_fn
 
 T_co = TypeVar("T_co", covariant=True)
 
@@ -59,7 +59,7 @@ def __init__(
     ) -> None:
         self.datapipe = datapipe
 
-        _check_lambda_fn(fn)
+        _check_unpickable_fn(fn)
         self.fn = fn  # type: ignore[assignment]
 
         assert batch_size > 0, "Batch size is required to be larger than 0!"
@@ -118,7 +118,7 @@ class FlatMapperIterDataPipe(IterDataPipe[T_co]):
     def __init__(self, datapipe: IterDataPipe, fn: Callable, input_col=None) -> None:
         self.datapipe = datapipe
 
-        _check_lambda_fn(fn)
+        _check_unpickable_fn(fn)
         self.fn = fn  # type: ignore[assignment]
         self.input_col = input_col
 

torchdata/datapipes/iter/util/cacheholder.py

@@ -27,7 +27,7 @@
     raise
 
 
-from torch.utils.data.datapipes.utils.common import _check_lambda_fn, DILL_AVAILABLE
+from torch.utils.data.datapipes.utils.common import _check_unpickable_fn, DILL_AVAILABLE
 
 from torch.utils.data.graph import traverse
 from torchdata.datapipes import functional_datapipe
@@ -184,7 +184,8 @@ def __init__(
     ):
         self.source_datapipe = source_datapipe
 
-        _check_lambda_fn(filepath_fn)
+        if filepath_fn is not None:
+            _check_unpickable_fn(filepath_fn)
         filepath_fn = _generator_to_list(filepath_fn) if inspect.isgeneratorfunction(filepath_fn) else filepath_fn
 
         if hash_dict is not None and hash_type not in ("sha256", "md5"):

torchdata/datapipes/iter/util/combining.py

@@ -9,7 +9,7 @@
 from typing import Callable, Iterator, Optional, TypeVar
 
 from torch.utils.data import functional_datapipe, IterDataPipe, MapDataPipe
-from torch.utils.data.datapipes.utils.common import _check_lambda_fn
+from torch.utils.data.datapipes.utils.common import _check_unpickable_fn
 
 T_co = TypeVar("T_co", covariant=True)
 
@@ -64,14 +64,14 @@ def __init__(
             raise TypeError(f"ref_datapipe must be a IterDataPipe, but its type is {type(ref_datapipe)} instead.")
         self.source_datapipe = source_datapipe
         self.ref_datapipe = ref_datapipe
-        _check_lambda_fn(key_fn)
+        _check_unpickable_fn(key_fn)
         self.key_fn = key_fn
         if ref_key_fn is not None:
-            _check_lambda_fn(ref_key_fn)
+            _check_unpickable_fn(ref_key_fn)
         self.ref_key_fn = key_fn if ref_key_fn is None else ref_key_fn
         self.keep_key = keep_key
         if merge_fn is not None:
-            _check_lambda_fn(merge_fn)
+            _check_unpickable_fn(merge_fn)
         self.merge_fn = merge_fn
         if buffer_size is not None and buffer_size <= 0:
             raise ValueError("'buffer_size' is required to be either None or a positive integer.")
@@ -185,10 +185,10 @@ def __init__(
             raise TypeError(f"map_datapipe must be a MapDataPipe, but its type is {type(map_datapipe)} instead.")
         self.source_iterdatapipe: IterDataPipe = source_iterdatapipe
         self.map_datapipe: MapDataPipe = map_datapipe
-        _check_lambda_fn(key_fn)
+        _check_unpickable_fn(key_fn)
         self.key_fn: Callable = key_fn
         if merge_fn is not None:
-            _check_lambda_fn(merge_fn)
+            _check_unpickable_fn(merge_fn)
         self.merge_fn: Optional[Callable] = merge_fn
         self.length: int = -1
 

torchdata/datapipes/iter/util/converter.py

@@ -9,7 +9,7 @@
 from typing import Callable, Dict, Optional
 
 from torch.utils.data import IterDataPipe, MapDataPipe
-from torch.utils.data.datapipes.utils.common import _check_lambda_fn, DILL_AVAILABLE
+from torch.utils.data.datapipes.utils.common import _check_unpickable_fn, DILL_AVAILABLE
 
 if DILL_AVAILABLE:
     import dill
@@ -52,7 +52,8 @@ def __init__(self, datapipe: IterDataPipe, key_value_fn: Optional[Callable] = No
         if not isinstance(datapipe, IterDataPipe):
             raise TypeError(f"IterToMapConverter can only apply on IterDataPipe, but found {type(datapipe)}")
         self.datapipe = datapipe
-        _check_lambda_fn(key_value_fn)
+        if key_value_fn is not None:
+            _check_unpickable_fn(key_value_fn)
         self.key_value_fn = key_value_fn  # type: ignore[assignment]
         self._map = None
         self._length = -1

torchdata/datapipes/iter/util/paragraphaggregator.py

@@ -6,7 +6,7 @@
 
 from typing import Callable, Iterator, List, Tuple, TypeVar
 
-from torch.utils.data.datapipes.utils.common import _check_lambda_fn
+from torch.utils.data.datapipes.utils.common import _check_unpickable_fn
 
 from torchdata.datapipes import functional_datapipe
 from torchdata.datapipes.iter import IterDataPipe
@@ -44,7 +44,7 @@ class ParagraphAggregatorIterDataPipe(IterDataPipe[Tuple[str, str]]):
 
     def __init__(self, source_datapipe: IterDataPipe[Tuple[str, T_co]], joiner: Callable = _default_line_join) -> None:
         self.source_datapipe: IterDataPipe[Tuple[str, T_co]] = source_datapipe
-        _check_lambda_fn(joiner)
+        _check_unpickable_fn(joiner)
         self.joiner: Callable = joiner
         self.buffer: List = []