BUG: raise on non-hashable Index name, closes pandas-dev#29069

Author: jbrockmendel

pandas/core/indexes/base.py

@@ -274,8 +274,7 @@ def __new__(
         from .interval import IntervalIndex
         from .category import CategoricalIndex
 
-        if name is None and hasattr(data, "name"):
-            name = data.name
+        name = maybe_extract_name(name, data)
 
         if isinstance(data, ABCPandasArray):
             # ensure users don't accidentally put a PandasArray in an index.
@@ -5464,3 +5463,17 @@ def default_index(n):
     from pandas.core.indexes.range import RangeIndex
 
     return RangeIndex(0, n, name=None)
+
+
+def maybe_extract_name(name, obj):
+    """
+    If no name is passed, then extract it from data, validating hashability.
+    """
+    if name is None and hasattr(obj, "name"):
+        name = obj.name
+
+    # GH#29069
+    if not is_hashable(name):
+        raise TypeError(f"Index.name must be a hashable type")
+
+    return name

pandas/core/indexes/category.py

@@ -29,7 +29,7 @@
 from pandas.core.base import _shared_docs
 import pandas.core.common as com
 import pandas.core.indexes.base as ibase
-from pandas.core.indexes.base import Index, _index_shared_docs
+from pandas.core.indexes.base import Index, _index_shared_docs, maybe_extract_name
 import pandas.core.missing as missing
 from pandas.core.ops import get_op_result_name
 
@@ -175,8 +175,7 @@ def __new__(
 
         dtype = CategoricalDtype._from_values_or_dtype(data, categories, ordered, dtype)
 
-        if name is None and hasattr(data, "name"):
-            name = data.name
+        name = maybe_extract_name(name, data)
 
         if not is_categorical_dtype(data):
             # don't allow scalars

pandas/core/indexes/datetimes.py

@@ -30,7 +30,7 @@
 )
 from pandas.core.base import _shared_docs
 import pandas.core.common as com
-from pandas.core.indexes.base import Index
+from pandas.core.indexes.base import Index, maybe_extract_name
 from pandas.core.indexes.datetimelike import (
     DatetimeIndexOpsMixin,
     DatetimelikeDelegateMixin,
@@ -253,8 +253,7 @@ def __new__(
 
         # - Cases checked above all return/raise before reaching here - #
 
-        if name is None and hasattr(data, "name"):
-            name = data.name
+        name = maybe_extract_name(name, data)
 
         dtarr = DatetimeArray._from_sequence(
             data,

pandas/core/indexes/interval.py

@@ -47,6 +47,7 @@
     _index_shared_docs,
     default_pprint,
     ensure_index,
+    maybe_extract_name,
 )
 from pandas.core.indexes.datetimes import DatetimeIndex, date_range
 from pandas.core.indexes.multi import MultiIndex
@@ -213,8 +214,7 @@ def __new__(
         cls, data, closed=None, dtype=None, copy=False, name=None, verify_integrity=True
     ):
 
-        if name is None and hasattr(data, "name"):
-            name = data.name
+        name = maybe_extract_name(name, data)
 
         with rewrite_exception("IntervalArray", cls.__name__):
             array = IntervalArray(

pandas/core/indexes/numeric.py

@@ -30,7 +30,12 @@
 from pandas._typing import Dtype
 from pandas.core import algorithms
 import pandas.core.common as com
-from pandas.core.indexes.base import Index, InvalidIndexError, _index_shared_docs
+from pandas.core.indexes.base import (
+    Index,
+    InvalidIndexError,
+    _index_shared_docs,
+    maybe_extract_name,
+)
 from pandas.core.ops import get_op_result_name
 
 _num_index_shared_docs = dict()
@@ -68,8 +73,7 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None):
         else:
             subarr = data
 
-        if name is None and hasattr(data, "name"):
-            name = data.name
+        name = maybe_extract_name(name, data)
         return cls._simple_new(subarr, name=name)
 
     @classmethod

pandas/core/indexes/period.py

@@ -25,7 +25,11 @@
 from pandas.core.base import _shared_docs
 import pandas.core.common as com
 import pandas.core.indexes.base as ibase
-from pandas.core.indexes.base import _index_shared_docs, ensure_index
+from pandas.core.indexes.base import (
+    _index_shared_docs,
+    ensure_index,
+    maybe_extract_name,
+)
 from pandas.core.indexes.datetimelike import (
     DatetimeIndexOpsMixin,
     DatetimelikeDelegateMixin,
@@ -184,8 +188,7 @@ def __new__(
             argument = list(set(fields) - valid_field_set)[0]
             raise TypeError(f"__new__() got an unexpected keyword argument {argument}")
 
-        if name is None and hasattr(data, "name"):
-            name = data.name
+        name = maybe_extract_name(name, data)
 
         if data is None and ordinal is None:
             # range-based.

pandas/core/indexes/range.py

@@ -26,7 +26,7 @@
 import pandas.core.common as com
 from pandas.core.construction import extract_array
 import pandas.core.indexes.base as ibase
-from pandas.core.indexes.base import Index, _index_shared_docs
+from pandas.core.indexes.base import Index, _index_shared_docs, maybe_extract_name
 from pandas.core.indexes.numeric import Int64Index
 from pandas.core.ops.common import unpack_zerodim_and_defer
 
@@ -85,10 +85,10 @@ def __new__(
     ):
 
         cls._validate_dtype(dtype)
+        name = maybe_extract_name(name, start)
 
         # RangeIndex
         if isinstance(start, RangeIndex):
-            name = start.name if name is None else name
             start = start._range
             return cls._simple_new(start, dtype=dtype, name=name)
 

pandas/core/indexes/timedeltas.py

@@ -25,7 +25,7 @@
 from pandas.core.arrays.timedeltas import TimedeltaArray, _is_convertible_to_td
 from pandas.core.base import _shared_docs
 import pandas.core.common as com
-from pandas.core.indexes.base import Index, _index_shared_docs
+from pandas.core.indexes.base import Index, _index_shared_docs, maybe_extract_name
 from pandas.core.indexes.datetimelike import (
     DatetimeIndexOpsMixin,
     DatetimelikeDelegateMixin,
@@ -163,6 +163,7 @@ def __new__(
         copy=False,
         name=None,
     ):
+        name = maybe_extract_name(name, data)
 
         if is_scalar(data):
             raise TypeError(

pandas/tests/indexes/common.py

@@ -103,6 +103,13 @@ def test_shift(self):
         with pytest.raises(NotImplementedError, match=msg):
             idx.shift(1, 2)
 
+    def test_constructor_name_unhashable(self):
+        # GH#29069 check that name is hashable
+        # See also same-named test in tests.series.test_constructors
+        idx = self.create_index()
+        with pytest.raises(TypeError, match="Index.name must be a hashable type"):
+            type(idx)(idx, name=[])
+
     def test_create_index_existing_name(self):
 
         # GH11193, when an existing index is passed, and a new name is not

pandas/tests/indexes/test_base.py

@@ -100,6 +100,7 @@ def test_constructor_copy(self, index):
         arr[0] = "SOMEBIGLONGSTRING"
         assert new_index[0] != "SOMEBIGLONGSTRING"
 
+        # FIXME: dont leave commented-out
         # what to do here?
         # arr = np.array(5.)
         # pytest.raises(Exception, arr.view, Index)