Add the deprecate_nonkeyword_arguments decorator and some tests for it.

Author: alexitkes

pandas/io/html.py

@@ -20,6 +20,8 @@
 from pandas.io.formats.printing import pprint_thing
 from pandas.io.parsers import TextParser
 
+from pandas.util._decorators import deprecate_nonkeyword_arguments
+
 _IMPORTS = False
 _HAS_BS4 = False
 _HAS_LXML = False
@@ -920,10 +922,10 @@ def _parse(flavor, io, match, attrs, encoding, displayed_only, **kwargs):
     return ret
 
 
+@deprecate_nonkeyword_arguments(version="1.0", allowed_args=['io', 'match'])
 def read_html(
     io,
     match=".+",
-    *,
     flavor=None,
     header=None,
     index_col=None,

pandas/io/json/_json.py

@@ -23,6 +23,8 @@
 from pandas.io.formats.printing import pprint_thing
 from pandas.io.parsers import _validate_integer
 
+from pandas.util._decorators import deprecate_nonkeyword_arguments
+
 from ._normalize import convert_to_line_delimits
 from ._table_schema import build_table_schema, parse_table_schema
 
@@ -331,9 +333,9 @@ def _write(
         return serialized
 
 
+@deprecate_nonkeyword_arguments(version="1.0", allowed_args=['path_or_buf'])
 def read_json(
     path_or_buf=None,
-    *,
     orient=None,
     typ="frame",
     dtype=None,

pandas/tests/util/test_deprecate_nonkeyword_arguments.py

@@ -0,0 +1,42 @@
+"""
+Tests for the `deprecate_nonkeyword_arguments` decorator
+"""
+
+from pandas.util._decorators import deprecate_nonkeyword_arguments
+
+import pandas.util.testing as tm
+
+
+@deprecate_nonkeyword_arguments(version="1.0", allowed_args=['a', 'b'])
+def f(a, b=0, c=0, d=0):
+    """
+    Sum of one to four numbers, the two last arguments
+    should be given as keyword arguments only
+    """
+    return a + b + c + d
+
+
+def test_two_arguments(x):
+    """
+    Check whether no future warning is produced if two
+    positional arguments given.
+    """
+    assert f(1, 5) = 6
+
+
+def test_two_arguments(x):
+    """
+    Check whether no future warning is produced if two
+    positional arguments and two keyword arguments are
+    given.
+    """
+    assert f(1, 3, c=3, d=5) = 12
+
+
+def test_four_arguments(x):
+    """
+    Check whether a future warning is produced if four
+    positional arguments given.
+    """
+    with tm.assert_produces_warning(FutureWarning):
+        assert f(1, 2, 3, 4) = 10

pandas/util/_decorators.py

@@ -212,6 +212,42 @@ def wrapper(*args, **kwargs):
     return _deprecate_kwarg
 
 
+def deprecate_nonkeyword_arguments(
+    version: str,
+    allowed_args:,
+    *,
+    stacklevel : int = 2
+) -> Callable
+    """
+    Decorator to deprecate a use of non-keyword arguments of a function.
+
+    Parameters
+    ----------
+    version : str
+        The version in which positional arguments will become
+        keyword-only.
+
+    allowed_args : list or int
+        In case of list, it must be the list of names of some
+        first arguments of the decorated functions that are
+        OK to be given as positional arguments. In case of an
+        integer, this is the number of positional arguments
+        that will stay positional.
+
+    stacklevel : int, default=2
+        The stack level for warnings.warn
+    """
+
+    def decorate(func):
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            return func(*args, **kwargs)
+
+        return wrapper
+
+    return decorate
+
+
 def rewrite_axis_style_signature(
     name: str, extra_params: List[Tuple[str, Any]]
 ) -> Callable: