Require keyword args for data iterator. (#8327)

python-package/xgboost/core.py

@@ -502,8 +502,8 @@ class DataIter(ABC):  # pylint: disable=too-many-instance-attributes
         pointer.
 
         """
-        @_deprecate_positional_args
-        def data_handle(
+        @require_pos_args(True)
+        def input_data(
             data: Any,
             *,
             feature_names: Optional[FeatureNames] = None,
@@ -528,7 +528,7 @@ class DataIter(ABC):  # pylint: disable=too-many-instance-attributes
                 **kwargs,
             )
         # pylint: disable=not-callable
-        return self._handle_exception(lambda: self.next(data_handle), 0)
+        return self._handle_exception(lambda: self.next(input_data), 0)
 
     @abstractmethod
     def reset(self) -> None:
@@ -554,7 +554,7 @@ class DataIter(ABC):  # pylint: disable=too-many-instance-attributes
         raise NotImplementedError()
 
 
-# Notice for `_deprecate_positional_args`
+# Notice for `require_pos_args`
 # Authors: Olivier Grisel
 #          Gael Varoquaux
 #          Andreas Mueller
@@ -563,20 +563,30 @@ class DataIter(ABC):  # pylint: disable=too-many-instance-attributes
 #          Nicolas Tresegnie
 #          Sylvain Marie
 # License: BSD 3 clause
-def _deprecate_positional_args(f: Callable[..., _T]) -> Callable[..., _T]:
+def require_pos_args(error: bool) -> Callable[[Callable[..., _T]], Callable[..., _T]]:
     """Decorator for methods that issues warnings for positional arguments
 
     Using the keyword-only argument syntax in pep 3102, arguments after the
-    * will issue a warning when passed as a positional argument.
+    * will issue a warning or error when passed as a positional argument.
 
     Modified from sklearn utils.validation.
 
     Parameters
     ----------
-    f : function
-        function to check arguments on
+    error :
+        Whether to throw an error or raise a warning.
     """
-    sig = signature(f)
+
+    def throw_if(func: Callable[..., _T]) -> Callable[..., _T]:
+        """Throw error/warning if there are positional arguments after the asterisk.
+
+        Parameters
+        ----------
+        f :
+            function to check arguments on.
+
+        """
+        sig = signature(func)
         kwonly_args = []
         all_args = []
 
@@ -586,28 +596,31 @@ def _deprecate_positional_args(f: Callable[..., _T]) -> Callable[..., _T]:
             elif param.kind == Parameter.KEYWORD_ONLY:
                 kwonly_args.append(name)
 
-    @wraps(f)
+        @wraps(func)
         def inner_f(*args: Any, **kwargs: Any) -> _T:
             extra_args = len(args) - len(all_args)
             if extra_args > 0:
                 # ignore first 'self' argument for instance methods
                 args_msg = [
-                f"{name}" for name, _ in zip(
-                    kwonly_args[:extra_args], args[-extra_args:]
-                )
+                    f"{name}"
+                    for name, _ in zip(kwonly_args[:extra_args], args[-extra_args:])
                 ]
                 # pylint: disable=consider-using-f-string
-            warnings.warn(
-                "Pass `{}` as keyword args.  Passing these as positional "
-                "arguments will be considered as error in future releases.".
-                format(", ".join(args_msg)), FutureWarning
-            )
+                msg = "Pass `{}` as keyword args.".format(", ".join(args_msg))
+                if error:
+                    raise TypeError(msg)
+                warnings.warn(msg, FutureWarning)
             for k, arg in zip(sig.parameters, args):
                 kwargs[k] = arg
-        return f(**kwargs)
+            return func(**kwargs)
 
         return inner_f
 
+    return throw_if
+
+
+_deprecate_positional_args = require_pos_args(False)
+
 
 class DMatrix:  # pylint: disable=too-many-instance-attributes,too-many-public-methods
     """Data Matrix used in XGBoost.

tests/python/testing.py

@@ -198,6 +198,10 @@ class IteratorForTest(xgb.core.DataIter):
     def next(self, input_data: Callable) -> int:
         if self.it == len(self.X):
             return 0
+
+        with pytest.raises(TypeError, match="keyword args"):
+            input_data(self.X[self.it], self.y[self.it], None)
+
         # Use copy to make sure the iterator doesn't hold a reference to the data.
         input_data(
             data=self.X[self.it].copy(),