ENH: set __module__ on merge functions in merge.py (#60266)

Author: chanshing

pandas/core/reshape/merge.py

@@ -39,7 +39,10 @@
     npt,
 )
 from pandas.errors import MergeError
-from pandas.util._decorators import cache_readonly
+from pandas.util._decorators import (
+    cache_readonly,
+    set_module,
+)
 from pandas.util._exceptions import find_stack_level
 
 from pandas.core.dtypes.base import ExtensionDtype
@@ -138,6 +141,7 @@
 _known = (np.ndarray, ExtensionArray, Index, ABCSeries)
 
 
+@set_module("pandas")
 def merge(
     left: DataFrame | Series,
     right: DataFrame | Series,
@@ -502,6 +506,7 @@ def _groupby_and_merge(
     return result, lby
 
 
+@set_module("pandas")
 def merge_ordered(
     left: DataFrame | Series,
     right: DataFrame | Series,
@@ -645,6 +650,7 @@ def _merger(x, y) -> DataFrame:
     return result
 
 
+@set_module("pandas")
 def merge_asof(
     left: DataFrame | Series,
     right: DataFrame | Series,

pandas/tests/api/test_api.py

@@ -417,6 +417,9 @@ def test_set_module():
     assert pd.Period.__module__ == "pandas"
     assert pd.Timestamp.__module__ == "pandas"
     assert pd.Timedelta.__module__ == "pandas"
+    assert pd.merge.__module__ == "pandas"
+    assert pd.merge_ordered.__module__ == "pandas"
+    assert pd.merge_asof.__module__ == "pandas"
     assert pd.read_csv.__module__ == "pandas"
     assert pd.read_table.__module__ == "pandas"
     assert pd.read_fwf.__module__ == "pandas"