BUG: bdate_range with "cbh" fails (#62873)

Author: natmokval

doc/source/whatsnew/v3.0.0.rst

@@ -961,6 +961,7 @@ Categorical
 ^^^^^^^^^^^
 - Bug in :class:`Categorical` where constructing from a pandas :class:`Series` or :class:`Index` with ``dtype='object'`` did not preserve the categories' dtype as ``object``; now the ``categories.dtype`` is preserved as ``object`` for these cases, while numpy arrays and Python sequences with ``dtype='object'`` continue to infer the most specific dtype (for example, ``str`` if all elements are strings) (:issue:`61778`)
 - Bug in :func:`Series.apply` where ``nan`` was ignored for :class:`CategoricalDtype` (:issue:`59938`)
+- Bug in :func:`bdate_range` raising ``ValueError`` with frequency ``freq="cbh"`` (:issue:`62849`)
 - Bug in :func:`testing.assert_index_equal` raising ``TypeError`` instead of ``AssertionError`` for incomparable ``CategoricalIndex`` when ``check_categorical=True`` and ``exact=False`` (:issue:`61935`)
 - Bug in :meth:`Categorical.astype` where ``copy=False`` would still trigger a copy of the codes (:issue:`62000`)
 - Bug in :meth:`DataFrame.pivot` and :meth:`DataFrame.set_index` raising an ``ArrowNotImplementedError`` for columns with pyarrow dictionary dtype (:issue:`53051`)

pandas/core/indexes/datetimes.py

@@ -1133,12 +1133,14 @@ def bdate_range(
         msg = "freq must be specified for bdate_range; use date_range instead"
         raise TypeError(msg)
 
-    if isinstance(freq, str) and freq.startswith("C"):
+    if isinstance(freq, str) and freq.upper().startswith("C"):
+        msg = f"invalid custom frequency string: {freq}"
+        if freq == "CBH":
+            raise ValueError(f"{msg}, did you mean cbh?")
         try:
             weekmask = weekmask or "Mon Tue Wed Thu Fri"
             freq = prefix_mapping[freq](holidays=holidays, weekmask=weekmask)
         except (KeyError, TypeError) as err:
-            msg = f"invalid custom frequency string: {freq}"
             raise ValueError(msg) from err
     elif holidays or weekmask:
         msg = (

pandas/tests/indexes/datetimes/test_date_range.py

@@ -1216,7 +1216,7 @@ def test_cdaterange_holidays_weekmask_requires_freqstr(self):
             )
 
     @pytest.mark.parametrize(
-        "freq", [freq for freq in prefix_mapping if freq.startswith("C")]
+        "freq", [freq for freq in prefix_mapping if freq.upper().startswith("C")]
     )
     def test_all_custom_freq(self, freq):
         # should not raise
@@ -1280,6 +1280,39 @@ def test_data_range_custombusinessday_partial_time(self, unit):
         )
         tm.assert_index_equal(result, expected)
 
+    def test_cdaterange_cbh(self):
+        # GH#62849
+        result = bdate_range(
+            "2009-03-13",
+            "2009-03-15",
+            freq="cbh",
+            weekmask="Mon Wed Fri",
+            holidays=["2009-03-14"],
+        )
+        expected = DatetimeIndex(
+            [
+                "2009-03-13 09:00:00",
+                "2009-03-13 10:00:00",
+                "2009-03-13 11:00:00",
+                "2009-03-13 12:00:00",
+                "2009-03-13 13:00:00",
+                "2009-03-13 14:00:00",
+                "2009-03-13 15:00:00",
+                "2009-03-13 16:00:00",
+            ],
+            dtype="datetime64[ns]",
+            freq="cbh",
+        )
+        tm.assert_index_equal(result, expected)
+
+    def test_cdaterange_deprecated_error_CBH(self):
+        # GH#62849
+        msg = "invalid custom frequency string: CBH, did you mean cbh?"
+        with pytest.raises(ValueError, match=msg):
+            bdate_range(
+                START, END, freq="CBH", weekmask="Mon Wed Fri", holidays=["2009-03-14"]
+            )
+
 
 class TestDateRangeNonNano:
     def test_date_range_reso_validation(self):