BUG: Timedelta with invalid keyword (pandas-dev#61883)

Author: jbrockmendel

doc/source/whatsnew/v3.0.0.rst

@@ -717,6 +717,7 @@ Datetimelike
 Timedelta
 ^^^^^^^^^
 - Accuracy improvement in :meth:`Timedelta.to_pytimedelta` to round microseconds consistently for large nanosecond based Timedelta (:issue:`57841`)
+- Bug in :class:`Timedelta` constructor failing to raise when passed an invalid keyword (:issue:`53801`)
 - Bug in :meth:`DataFrame.cumsum` which was raising ``IndexError`` if dtype is ``timedelta64[ns]`` (:issue:`57956`)
 
 Timezones

pandas/_libs/tslibs/timedeltas.pyx

@@ -2006,6 +2006,20 @@ class Timedelta(_Timedelta):
                            "milliseconds", "microseconds", "nanoseconds"}
 
     def __new__(cls, object value=_no_input, unit=None, **kwargs):
+        unsupported_kwargs = set(kwargs)
+        unsupported_kwargs.difference_update(cls._req_any_kwargs_new)
+        if unsupported_kwargs or (
+            value is _no_input and
+            not cls._req_any_kwargs_new.intersection(kwargs)
+        ):
+            raise ValueError(
+                # GH#53801
+                "cannot construct a Timedelta from the passed arguments, "
+                "allowed keywords are "
+                "[weeks, days, hours, minutes, seconds, "
+                "milliseconds, microseconds, nanoseconds]"
+            )
+
         if value is _no_input:
             if not len(kwargs):
                 raise ValueError("cannot construct a Timedelta without a "
@@ -2014,16 +2028,6 @@ class Timedelta(_Timedelta):
 
             kwargs = {key: _to_py_int_float(kwargs[key]) for key in kwargs}
 
-            unsupported_kwargs = set(kwargs)
-            unsupported_kwargs.difference_update(cls._req_any_kwargs_new)
-            if unsupported_kwargs or not cls._req_any_kwargs_new.intersection(kwargs):
-                raise ValueError(
-                    "cannot construct a Timedelta from the passed arguments, "
-                    "allowed keywords are "
-                    "[weeks, days, hours, minutes, seconds, "
-                    "milliseconds, microseconds, nanoseconds]"
-                )
-
             # GH43764, convert any input to nanoseconds first and then
             # create the timedelta. This ensures that any potential
             # nanosecond contributions from kwargs parsed as floats

pandas/tests/tslibs/test_timedeltas.py

@@ -104,6 +104,10 @@ def test_kwarg_assertion(kwargs):
     with pytest.raises(ValueError, match=re.escape(err_message)):
         Timedelta(**kwargs)
 
+    with pytest.raises(ValueError, match=re.escape(err_message)):
+        # GH#53801 'unit' misspelled as 'units'
+        Timedelta(1, units="hours")
+
 
 class TestArrayToTimedelta64:
     def test_array_to_timedelta64_string_with_unit_2d_raises(self):