Add positional args support for fdl.Config

PiperOrigin-RevId: 549731020

fiddle/_src/building.py

@@ -95,14 +95,21 @@ def _make_message(current_path: daglish.Path, buildable: config_lib.Buildable,
 
 def call_buildable(
     buildable: config_lib.Buildable,
-    arguments: Dict[str, Any],
+    kwargs: Dict[str, Any],
     *,
     current_path: daglish.Path,
 ) -> Any:
-  make_message = functools.partial(_make_message, current_path, buildable,
-                                   arguments)
+  """Run the __build__ method on a Buildable given keyword arguments."""
+  make_message = functools.partial(
+      _make_message, current_path, buildable, kwargs
+  )
+  args = []
+  for name in buildable.__positional_arg_names__:
+    if name in kwargs:
+      args.append(kwargs.pop(name))
+  args.extend(kwargs.pop('__args__', []))
   with reraised_exception.try_with_lazy_message(make_message):
-    return buildable.__build__(**arguments)
+    return buildable.__build__(*args, **kwargs)
 
 
 # Define typing overload for `build(Partial[T])`

fiddle/_src/config.py

@@ -26,7 +26,7 @@
 import itertools
 import logging
 import types
-from typing import Any, Callable, Collection, Dict, FrozenSet, Generic, Iterable, Mapping, NamedTuple, Optional, Set, Tuple, Type, TypeVar, Union
+from typing import Any, Callable, Collection, Dict, FrozenSet, Generic, Iterable, List, Mapping, NamedTuple, Optional, Set, Tuple, Type, TypeVar, Union
 
 from fiddle._src import arg_factory
 from fiddle._src import daglish
@@ -223,6 +223,8 @@ class Buildable(Generic[T], metaclass=abc.ABCMeta):
   __arguments__: Dict[str, Any]
   __argument_history__: history.History
   __argument_tags__: Dict[str, Set[tag_type.TagType]]
+  __positional_arg_names__: List[str]
+  __has_var_positional__: bool
   _has_var_keyword: bool
 
   def __init__(
@@ -245,19 +247,23 @@ def __init__(
     super().__setattr__('__argument_history__', arg_history)
     super().__setattr__('__argument_tags__', collections.defaultdict(set))
 
+    positional_arguments = ()
     arguments = signature.bind_partial(*args, **kwargs).arguments
     for name in list(arguments.keys()):  # Make a copy in case we mutate.
       param = signature.parameters[name]
       if param.kind == param.VAR_POSITIONAL:
-        # TODO(b/197367863): Add *args support.
-        err_msg = (
-            'Variable positional arguments (aka `*args`) not supported. '
-            f'Found param `{name}` in `{fn_or_cls}`.'
-        )
-        raise NotImplementedError(err_msg)
+        positional_arguments = arguments.pop(param.name)
       elif param.kind == param.VAR_KEYWORD:
         arguments.update(arguments.pop(param.name))
 
+    if positional_arguments:
+      self.__arguments__['__args__'] = list(positional_arguments)
+      self.__argument_history__.add_new_value(
+          '__args__', self.__arguments__['__args__']
+      )
+
+    for i, value in enumerate(positional_arguments):
+      self[i] = value
     for name, value in arguments.items():
       setattr(self, name, value)
 
@@ -286,10 +292,25 @@ def __init_callable__(
     super().__setattr__('__arguments__', {})
     signature = signatures.get_signature(fn_or_cls)
     super().__setattr__('__signature__', signature)
-    has_var_keyword = any(
-        param.kind == param.VAR_KEYWORD
-        for param in signature.parameters.values()
-    )
+
+    # If *args exists, we must pass things before it in positional format. This
+    # list tracks those arguments.
+    maybe_positional_args = []
+
+    positional_only_args = []
+    has_var_positional, has_var_keyword = False, False
+    for param in signature.parameters.values():
+      if param.kind == param.VAR_POSITIONAL:
+        has_var_positional = True
+        positional_only_args.extend(maybe_positional_args)
+      elif param.kind == param.VAR_KEYWORD:
+        has_var_keyword = True
+      elif param.kind == param.POSITIONAL_ONLY:
+        positional_only_args.append(param.name)
+      elif param.kind == param.POSITIONAL_OR_KEYWORD:
+        maybe_positional_args.append(param.name)
+    super().__setattr__('__positional_arg_names__', positional_only_args)
+    super().__setattr__('__has_var_positional__', has_var_positional)
     super().__setattr__('_has_var_keyword', has_var_keyword)
     return signature
 
@@ -326,6 +347,14 @@ def __path_elements__(self) -> Tuple[daglish.Attr]:
 
   def __getattr__(self, name: str):
     """Get parameter with given ``name``."""
+    if name == 'posargs':
+      if not self.__has_var_positional__:
+        raise TypeError(
+            "This function doesn't have variadic positional arguments (*args). "
+            'Please set other (including positional-only) arguments by name.'
+        )
+
+      name = '__args__'
     value = self.__arguments__.get(name, _UNSET_SENTINEL)
 
     if value is not _UNSET_SENTINEL:
@@ -387,6 +416,34 @@ def __validate_param_name__(self, name) -> None:
         )
       raise TypeError(err_msg)
 
+  def __setitem__(self, key: Any, value: Any):
+    if not isinstance(key, (int, slice)):
+      raise TypeError(
+          'Setting arguments by index is only supported for variadic '
+          "arguments (*args), like my_config[4] = 'foo'."
+      )
+    if not self.__has_var_positional__:
+      raise TypeError(
+          "This function doesn't have variadic positional arguments (*args). "
+          'Please set other (including positional-only) arguments by name.'
+      )
+
+    # In the future, use a specialized history-tracking list.
+    if '__args__' not in self.__arguments__:
+      self.__arguments__['__args__'] = []
+      self.__argument_history__.add_new_value('__args__', [])
+    args = self.__arguments__['__args__']
+    args[key] = value
+
+  def __getitem__(self, key: Any):
+    if not isinstance(key, slice):
+      raise TypeError(
+          'Getting arguments by index is only supported when using slice, '
+          'for example `v = my_config[:2]`, or using the `posargs` attr '
+          f'instead, like v = my_config[0]. Got {type(key)} type as key.'
+      )
+    return self.posargs[key]
+
   def __setattr__(self, name: str, value: Any):
     """Sets parameter ``name`` to ``value``."""
 
@@ -950,13 +1007,63 @@ def update_callable(
   # will result in duplicate history entries.
   original_args = buildable.__arguments__
   signature = signatures.get_signature(new_callable)
+  # Update the signature early so that we can set arguments by position
+  object.__setattr__(buildable, '__signature__', signature)
+
   if any(
       param.kind == param.VAR_POSITIONAL
       for param in signature.parameters.values()
   ):
-    raise NotImplementedError(
-        'Variable positional arguments (aka `*args`) not supported.'
-    )
+    # Both callables have *args
+    if buildable.__has_var_positional__:
+      args_ptr = -1
+      consumed_args = 0
+      for idx, arg in enumerate(signature.parameters.keys()):
+        if arg not in original_args.keys():
+          args_ptr = idx
+          break
+      all_args_key = list(signature.parameters.keys())
+      while args_ptr < len(all_args_key):
+        key = all_args_key[args_ptr]
+        param = signature.parameters[key]
+        if param.kind == param.VAR_POSITIONAL:
+          break
+        else:
+          value = original_args['__args__'][args_ptr]
+          buildable.__setattr__(key, value)
+          args_ptr += 1
+        consumed_args += 1
+
+      buildable.__arguments__['__args__'] = buildable.__arguments__['__args__'][
+          consumed_args:
+      ]
+    # Only new callable has *args
+    else:
+      object.__setattr__(buildable, '__args__', [])
+      buildable.__argument_history__.add_new_value('__args__', [])
+  else:
+    # If only the original config has *args
+    if buildable.__has_var_positional__:
+      args_start_at = -1
+      for idx, arg in enumerate(signature.parameters.keys()):
+        if arg not in original_args.keys():
+          args_start_at = idx
+          break
+
+      if len(signature.parameters) < args_start_at + len(
+          original_args['__args__']
+      ):
+        if not drop_invalid_args:
+          raise ValueError(
+              'new_callable does not have enough arguments when unpack *args: '
+              f'{original_args["__args__"]} from the original buildable.'
+          )
+      arg_keys = list(signature.parameters.keys())[args_start_at:]
+      for arg, value in zip(arg_keys, original_args['__args__']):
+        buildable.__setattr__(arg, value)
+      del buildable.__args__
+      object.__setattr__(buildable, '__has_var_positional__', False)
+
   has_var_keyword = any(
       param.kind == param.VAR_KEYWORD for param in signature.parameters.values()
   )
@@ -976,7 +1083,6 @@ def update_callable(
         )
 
   object.__setattr__(buildable, '__fn_or_cls__', new_callable)
-  object.__setattr__(buildable, '__signature__', signature)
   object.__setattr__(buildable, '_has_var_keyword', has_var_keyword)
   buildable.__argument_history__.add_new_value('__fn_or_cls__', new_callable)
 

fiddle/_src/config_test.py

@@ -224,6 +224,84 @@ def test_config_for_functions_with_var_args_and_kwargs(self):
         'kwargs': 'kwarg_called_kwarg'
     })
 
+  # "args" below refer to positional arguments, typcally `*args``
+  def test_args_config_access(self):
+    fn_config = fdl.Config(fn_with_var_args, 'foo', 'bar', 'baz')
+
+    with self.subTest('ordered_arguments'):
+      self.assertEqual(
+          fdl.ordered_arguments(fn_config),
+          {
+              'arg1': 'foo',
+              '__args__': ['bar', 'baz'],
+          },
+      )
+
+    with self.subTest('posargs_access'):
+      self.assertEqual(fn_config.posargs[0], 'bar')
+      self.assertEqual(fn_config.posargs[1], 'baz')
+      self.assertSequenceEqual(fn_config.posargs, ['bar', 'baz'])
+
+    with self.subTest('index_access'):
+      with self.assertRaisesRegex(
+          TypeError,
+          'Getting arguments by index is only supported when using slice',
+      ):
+        _ = fn_config[0]
+
+    with self.subTest('slice_access'):
+      self.assertEmpty(fn_config[:0])
+      self.assertSequenceEqual(fn_config[:1], ['bar'])
+      self.assertSequenceEqual(fn_config[:], ['bar', 'baz'])
+
+  def test_args_config_posargs_append(self):
+    fn_config = fdl.Config(fn_with_var_args, 'foo', 'bar', 'baz')
+    fn_config.posargs.append('foo')
+    self.assertSequenceEqual(fn_config.posargs, ['bar', 'baz', 'foo'])
+
+  def test_args_config_slice_mutation(self):
+    fn_config = fdl.Config(fn_with_var_args, 'foo', 'bar', 'baz')
+    self.assertSequenceEqual(fn_config[:], ['bar', 'baz'])
+    fn_config[:1] = ['zero', 'one']
+    self.assertSequenceEqual(fn_config[:], ['zero', 'one', 'baz'])
+
+  def test_args_config_shallow_copy(self):
+    fn_config = fdl.Config(fn_with_var_args, 'foo', 'bar', 'baz')
+    self.assertLen(fn_config[:], 2)
+    a_copy = fn_config[:]
+    a_copy.append('foo')
+    self.assertLen(fn_config[:], 2)
+    self.assertLen(a_copy, 3)
+
+  def test_index_mutation(self):
+    fn_config = fdl.Config(fn_with_var_args, 'foo', 'bar', 'baz')
+    fn_config[0] = 'foo'
+    self.assertEqual(fn_config.posargs[0], 'foo')
+    fn_config[-1] = 'last'
+    self.assertLen(fn_config.posargs, 2)
+    self.assertEqual(fn_config.posargs[1], 'last')
+    self.assertEqual(fn_config.posargs[-1], 'last')
+
+  def test_index_out_of_range(self):
+    fn_config = fdl.Config(fn_with_var_args, 'foo', 'bar', 'baz')
+    self.assertLen(fn_config[:], 2)
+    with self.assertRaisesRegex(
+        IndexError, 'list assignment index out of range'
+    ):
+      fn_config[2] = 'index-2'
+
+  def test_args_config_build(self):
+    fn_config = fdl.Config(fn_with_var_args, 'foo', 'bar', 'baz')
+    fn_args = fdl.build(fn_config)
+    self.assertEqual(
+        fn_args,
+        {
+            'arg1': 'foo',
+            'args': ('bar', 'baz'),
+            'kwarg1': None,
+        },
+    )
+
   def test_config_for_dicts(self):
     dict_config = fdl.Config(dict, a=1, b=2)
     dict_config.c = 3
@@ -858,12 +936,6 @@ def test_nonexistent_var_args_parameter_error(self):
     with self.assertRaisesRegex(TypeError, expected_msg):
       fn_config.args = (1, 2, 3)
 
-  def test_unsupported_var_args_error(self):
-    expected_msg = (r'Variable positional arguments \(aka `\*args`\) not '
-                    r'supported\.')
-    with self.assertRaisesRegex(NotImplementedError, expected_msg):
-      fdl.Config(fn_with_var_args, 1, 2, 3)
-
   def test_build_inside_build(self):
 
     def inner_build(x: int) -> str:
@@ -1211,11 +1283,37 @@ def test_update_callable_new_kwargs(self):
         }
     }, fdl.build(cfg))
 
-  def test_update_callable_varargs(self):
-    cfg = fdl.Config(fn_with_var_kwargs, 1, 2)
-    with self.assertRaisesRegex(NotImplementedError,
-                                'Variable positional arguments'):
-      fdl.update_callable(cfg, fn_with_var_args_and_kwargs)
+  def test_update_args_to_args(self):
+    cfg = fdl.Config(fn_with_var_args, 1, 2, kwarg1=3)
+    fdl.update_callable(cfg, fn_with_var_args_and_kwargs)
+    self.assertEqual(
+        cfg.__arguments__, {'arg1': 1, '__args__': [2], 'kwarg1': 3}
+    )
+    self.assertEqual(
+        {'arg1': 1, 'args': (2,), 'kwarg1': 3, 'kwargs': {}}, fdl.build(cfg)
+    )
+
+  def test_update_args_to_no_args(self):
+    cfg = fdl.Config(fn_with_var_args, 1, 2, kwarg1=3)
+    fdl.update_callable(cfg, basic_fn)
+    cfg.arg2 = 22
+    self.assertEqual(cfg.__arguments__, {'arg1': 1, 'arg2': 22, 'kwarg1': 3})
+    self.assertEqual(
+        {'arg1': 1, 'arg2': 22, 'kwarg1': 3, 'kwarg2': None}, fdl.build(cfg)
+    )
+
+  def test_update_args_kwargs(self):
+    def my_fn(*args, **kwargs):
+      del args, kwargs
+
+    cfg = fdl.Config(my_fn, 1, 2, 3, kwarg1=4, kwarg2=5)
+    cfg.posargs[0] = 10
+    cfg.kwarg1 = 40
+    config_lib.update_callable(cfg, fn_with_var_args_and_kwargs)
+    self.assertEqual(
+        cfg.__arguments__,
+        {'arg1': 10, '__args__': [2, 3], 'kwarg1': 40, 'kwarg2': 5},
+    )
 
   def test_get_callable(self):
     cfg = fdl.Config(basic_fn)

fiddle/_src/mutate_buildable.py

@@ -17,9 +17,16 @@
 
 from fiddle._src import config
 
-_buildable_internals_keys = ('__fn_or_cls__', '__signature__', '__arguments__',
-                             '_has_var_keyword', '__argument_tags__',
-                             '__argument_history__')
+_buildable_internals_keys = (
+    '__fn_or_cls__',
+    '__signature__',
+    '__arguments__',
+    '_has_var_keyword',
+    '__argument_tags__',
+    '__argument_history__',
+    '__has_var_positional__',
+    '__positional_arg_names__',
+)
 
 
 def move_buildable_internals(*, source: config.Buildable,