Enhance HfArgumentParser functionality and ease of use (#20323)

* Enhance HfArgumentParser

* Fix type hints for older python versions

* Fix and add tests (+formatting)

* Add changes

* doc-builder formatting

* Remove unused import "Call"

src/transformers/hf_argparser.py

@@ -20,11 +20,19 @@ from copy import copy
 from enum import Enum
 from inspect import isclass
 from pathlib import Path
-from typing import Any, Dict, Iterable, NewType, Optional, Tuple, Union, get_type_hints
+from typing import Any, Callable, Dict, Iterable, List, NewType, Optional, Tuple, Union, get_type_hints
 
 import yaml
 
 
+try:
+    # For Python versions <3.8, Literal is not in typing: https://peps.python.org/pep-0586/
+    from typing import Literal
+except ImportError:
+    # For Python 3.7
+    from typing_extensions import Literal
+
+
 DataClass = NewType("DataClass", Any)
 DataClassType = NewType("DataClassType", Any)
 
@@ -43,6 +51,68 @@ def string_to_bool(v):
         )
 
 
+def make_choice_type_function(choices: list) -> Callable[[str], Any]:
+    """
+    Creates a mapping function from each choices string representation to the actual value. Used to support multiple
+    value types for a single argument.
+
+    Args:
+        choices (list): List of choices.
+
+    Returns:
+        Callable[[str], Any]: Mapping function from string representation to actual value for each choice.
+    """
+    str_to_choice = {str(choice): choice for choice in choices}
+    return lambda arg: str_to_choice.get(arg, arg)
+
+
+def HfArg(
+    *,
+    aliases: Union[str, List[str]] = None,
+    help: str = None,
+    default: Any = dataclasses.MISSING,
+    default_factory: Callable[[], Any] = dataclasses.MISSING,
+    metadata: dict = None,
+    **kwargs,
+) -> dataclasses.Field:
+    """Argument helper enabling a concise syntax to create dataclass fields for parsing with `HfArgumentParser`.
+
+    Example comparing the use of `HfArg` and `dataclasses.field`:
+    ```
+    @dataclass
+    class Args:
+        regular_arg: str = dataclasses.field(default="Huggingface", metadata={"aliases": ["--example", "-e"], "help": "This syntax could be better!"})
+        hf_arg: str = HfArg(default="Huggingface", aliases=["--example", "-e"], help="What a nice syntax!")
+    ```
+
+    Args:
+        aliases (Union[str, List[str]], optional):
+            Single string or list of strings of aliases to pass on to argparse, e.g. `aliases=["--example", "-e"]`.
+            Defaults to None.
+        help (str, optional): Help string to pass on to argparse that can be displayed with --help. Defaults to None.
+        default (Any, optional):
+            Default value for the argument. If not default or default_factory is specified, the argument is required.
+            Defaults to dataclasses.MISSING.
+        default_factory (Callable[[], Any], optional):
+            The default_factory is a 0-argument function called to initialize a field's value. It is useful to provide
+            default values for mutable types, e.g. lists: `default_factory=list`. Mutually exclusive with `default=`.
+            Defaults to dataclasses.MISSING.
+        metadata (dict, optional): Further metadata to pass on to `dataclasses.field`. Defaults to None.
+
+    Returns:
+        Field: A `dataclasses.Field` with the desired properties.
+    """
+    if metadata is None:
+        # Important, don't use as default param in function signature because dict is mutable and shared across function calls
+        metadata = {}
+    if aliases is not None:
+        metadata["aliases"] = aliases
+    if help is not None:
+        metadata["help"] = help
+
+    return dataclasses.field(metadata=metadata, default=default, default_factory=default_factory, **kwargs)
+
+
 class HfArgumentParser(ArgumentParser):
     """
     This subclass of `argparse.ArgumentParser` uses type hints on dataclasses to generate arguments.
@@ -84,6 +154,10 @@ class HfArgumentParser(ArgumentParser):
                 "`typing.get_type_hints` method by default"
             )
 
+        aliases = kwargs.pop("aliases", [])
+        if isinstance(aliases, str):
+            aliases = [aliases]
+
         origin_type = getattr(field.type, "__origin__", field.type)
         if origin_type is Union:
             if str not in field.type.__args__ and (
@@ -108,9 +182,14 @@ class HfArgumentParser(ArgumentParser):
         # A variable to store kwargs for a boolean field, if needed
         # so that we can init a `no_*` complement argument (see below)
         bool_kwargs = {}
-        if isinstance(field.type, type) and issubclass(field.type, Enum):
+        if origin_type is Literal or (isinstance(field.type, type) and issubclass(field.type, Enum)):
+            if origin_type is Literal:
+                kwargs["choices"] = field.type.__args__
+            else:
                 kwargs["choices"] = [x.value for x in field.type]
-            kwargs["type"] = type(kwargs["choices"][0])
+
+            kwargs["type"] = make_choice_type_function(kwargs["choices"])
+
             if field.default is not dataclasses.MISSING:
                 kwargs["default"] = field.default
             else:
@@ -146,7 +225,7 @@ class HfArgumentParser(ArgumentParser):
                 kwargs["default"] = field.default_factory()
             else:
                 kwargs["required"] = True
-        parser.add_argument(field_name, **kwargs)
+        parser.add_argument(field_name, *aliases, **kwargs)
 
         # Add a complement `no_*` argument for a boolean field AFTER the initial field has already been added.
         # Order is important for arguments with the same destination!
@@ -178,7 +257,12 @@ class HfArgumentParser(ArgumentParser):
             self._parse_dataclass_field(parser, field)
 
     def parse_args_into_dataclasses(
-        self, args=None, return_remaining_strings=False, look_for_args_file=True, args_filename=None
+        self,
+        args=None,
+        return_remaining_strings=False,
+        look_for_args_file=True,
+        args_filename=None,
+        args_file_flag=None,
     ) -> Tuple[DataClass, ...]:
         """
         Parse command-line args into instances of the specified dataclass types.
@@ -196,6 +280,9 @@ class HfArgumentParser(ArgumentParser):
                 process, and will append its potential content to the command line args.
             args_filename:
                 If not None, will uses this file instead of the ".args" file specified in the previous argument.
+            args_file_flag:
+                If not None, will look for a file in the command-line args specified with this flag. The flag can be
+                specified multiple times and precedence is determined by the order (last one wins).
 
         Returns:
             Tuple consisting of:
@@ -205,17 +292,36 @@ class HfArgumentParser(ArgumentParser):
                   after initialization.
                 - The potential list of remaining argument strings. (same as argparse.ArgumentParser.parse_known_args)
         """
-        if args_filename or (look_for_args_file and len(sys.argv)):
+
+        if args_file_flag or args_filename or (look_for_args_file and len(sys.argv)):
+            args_files = []
+
             if args_filename:
-                args_file = Path(args_filename)
-            else:
-                args_file = Path(sys.argv[0]).with_suffix(".args")
+                args_files.append(Path(args_filename))
+            elif look_for_args_file and len(sys.argv):
+                args_files.append(Path(sys.argv[0]).with_suffix(".args"))
+
+            # args files specified via command line flag should overwrite default args files so we add them last
+            if args_file_flag:
+                # Create special parser just to extract the args_file_flag values
+                args_file_parser = ArgumentParser()
+                args_file_parser.add_argument(args_file_flag, type=str, action="append")
 
+                # Use only remaining args for further parsing (remove the args_file_flag)
+                cfg, args = args_file_parser.parse_known_args(args=args)
+                cmd_args_file_paths = vars(cfg).get(args_file_flag.lstrip("-"), None)
+
+                if cmd_args_file_paths:
+                    args_files.extend([Path(p) for p in cmd_args_file_paths])
+
+            file_args = []
+            for args_file in args_files:
                 if args_file.exists():
-                fargs = args_file.read_text().split()
-                args = fargs + args if args is not None else fargs + sys.argv[1:]
-                # in case of duplicate arguments the first one has precedence
-                # so we append rather than prepend.
+                    file_args += args_file.read_text().split()
+
+            # in case of duplicate arguments the last one has precedence
+            # args specified via the command line should overwrite args from files, so we add them last
+            args = file_args + args if args is not None else file_args + sys.argv[1:]
         namespace, remaining_args = self.parse_known_args(args=args)
         outputs = []
         for dtype in self.dataclass_types:

tests/utils/test_hf_argparser.py

@@ -25,7 +25,15 @@ from typing import List, Optional
 
 import yaml
 from transformers import HfArgumentParser, TrainingArguments
-from transformers.hf_argparser import string_to_bool
+from transformers.hf_argparser import make_choice_type_function, string_to_bool
+
+
+try:
+    # For Python versions <3.8, Literal is not in typing: https://peps.python.org/pep-0586/
+    from typing import Literal
+except ImportError:
+    # For Python 3.7
+    from typing_extensions import Literal
 
 
 def list_field(default=None, metadata=None):
@@ -58,6 +66,12 @@ class BasicEnum(Enum):
     toto = "toto"
 
 
+class MixedTypeEnum(Enum):
+    titi = "titi"
+    toto = "toto"
+    fourtytwo = 42
+
+
 @dataclass
 class EnumExample:
     foo: BasicEnum = "toto"
@@ -66,6 +80,14 @@ class EnumExample:
         self.foo = BasicEnum(self.foo)
 
 
+@dataclass
+class MixedTypeEnumExample:
+    foo: MixedTypeEnum = "toto"
+
+    def __post_init__(self):
+        self.foo = MixedTypeEnum(self.foo)
+
+
 @dataclass
 class OptionalExample:
     foo: Optional[int] = None
@@ -111,6 +133,14 @@ class HfArgumentParserTest(unittest.TestCase):
         for x, y in zip(a._actions, b._actions):
             xx = {k: v for k, v in vars(x).items() if k != "container"}
             yy = {k: v for k, v in vars(y).items() if k != "container"}
+
+            # Choices with mixed type have custom function as "type"
+            # So we need to compare results directly for equality
+            if xx.get("choices", None) and yy.get("choices", None):
+                for expected_choice in yy["choices"] + xx["choices"]:
+                    self.assertEqual(xx["type"](expected_choice), yy["type"](expected_choice))
+                del xx["type"], yy["type"]
+
             self.assertEqual(xx, yy)
 
     def test_basic(self):
@@ -163,21 +193,56 @@ class HfArgumentParserTest(unittest.TestCase):
         self.assertEqual(args, Namespace(foo=False, baz=False, opt=False))
 
     def test_with_enum(self):
-        parser = HfArgumentParser(EnumExample)
+        parser = HfArgumentParser(MixedTypeEnumExample)
 
         expected = argparse.ArgumentParser()
-        expected.add_argument("--foo", default="toto", choices=["titi", "toto"], type=str)
+        expected.add_argument(
+            "--foo",
+            default="toto",
+            choices=["titi", "toto", 42],
+            type=make_choice_type_function(["titi", "toto", 42]),
+        )
         self.argparsersEqual(parser, expected)
 
         args = parser.parse_args([])
         self.assertEqual(args.foo, "toto")
         enum_ex = parser.parse_args_into_dataclasses([])[0]
-        self.assertEqual(enum_ex.foo, BasicEnum.toto)
+        self.assertEqual(enum_ex.foo, MixedTypeEnum.toto)
 
         args = parser.parse_args(["--foo", "titi"])
         self.assertEqual(args.foo, "titi")
         enum_ex = parser.parse_args_into_dataclasses(["--foo", "titi"])[0]
-        self.assertEqual(enum_ex.foo, BasicEnum.titi)
+        self.assertEqual(enum_ex.foo, MixedTypeEnum.titi)
+
+        args = parser.parse_args(["--foo", "42"])
+        self.assertEqual(args.foo, 42)
+        enum_ex = parser.parse_args_into_dataclasses(["--foo", "42"])[0]
+        self.assertEqual(enum_ex.foo, MixedTypeEnum.fourtytwo)
+
+    def test_with_literal(self):
+        @dataclass
+        class LiteralExample:
+            foo: Literal["titi", "toto", 42] = "toto"
+
+        parser = HfArgumentParser(LiteralExample)
+
+        expected = argparse.ArgumentParser()
+        expected.add_argument(
+            "--foo",
+            default="toto",
+            choices=("titi", "toto", 42),
+            type=make_choice_type_function(["titi", "toto", 42]),
+        )
+        self.argparsersEqual(parser, expected)
+
+        args = parser.parse_args([])
+        self.assertEqual(args.foo, "toto")
+
+        args = parser.parse_args(["--foo", "titi"])
+        self.assertEqual(args.foo, "titi")
+
+        args = parser.parse_args(["--foo", "42"])
+        self.assertEqual(args.foo, 42)
 
     def test_with_list(self):
         parser = HfArgumentParser(ListExample)
@@ -222,7 +287,12 @@ class HfArgumentParserTest(unittest.TestCase):
         expected = argparse.ArgumentParser()
         expected.add_argument("--required_list", nargs="+", type=int, required=True)
         expected.add_argument("--required_str", type=str, required=True)
-        expected.add_argument("--required_enum", type=str, choices=["titi", "toto"], required=True)
+        expected.add_argument(
+            "--required_enum",
+            type=make_choice_type_function(["titi", "toto"]),
+            choices=["titi", "toto"],
+            required=True,
+        )
         self.argparsersEqual(parser, expected)
 
     def test_with_string_literal_annotation(self):
@@ -230,7 +300,12 @@ class HfArgumentParserTest(unittest.TestCase):
 
         expected = argparse.ArgumentParser()
         expected.add_argument("--foo", type=int, required=True)
-        expected.add_argument("--required_enum", type=str, choices=["titi", "toto"], required=True)
+        expected.add_argument(
+            "--required_enum",
+            type=make_choice_type_function(["titi", "toto"]),
+            choices=["titi", "toto"],
+            required=True,
+        )
         expected.add_argument("--opt", type=string_to_bool, default=None)
         expected.add_argument("--baz", default="toto", type=str, help="help message")
         expected.add_argument("--foo_str", nargs="+", default=["Hallo", "Bonjour", "Hello"], type=str)