BUG: Improve Index level validation to reject all NA-like values and …

…enhance error handling for boolean levels

pandas/core/indexes/base.py

@@ -2085,20 +2085,24 @@ def _validate_index_level(self, level) -> None:
 
  """
  # Explicitly raise for missing/null values to match pandas convention
+ # Also reject all NA-like values (np.nan, pd.NA, pd.NaT, etc.)
  if isna(level):
  raise KeyError(
  "Requested level is NA/NaN/NaT, which is not a valid level name"
  )
 
- # Standard integer check, but reject bool
- if lib.is_integer(level) and not isinstance(level, bool):
- # If the index itself is named as integer, accept
- if lib.is_integer(self.name) and level == self.name:
- return
- # Only allow 0 and -1 for a single-level Index
- if level in (0, -1):
- return
- if level < 0:
+ # Reject booleans unless the index name is actually a boolean and matches
+ if isinstance(level, bool):
+ if level != self.name:
+ raise KeyError(
+ f"Requested level ({level}) does not match index name ({self.name})"
+ )
+ return
+
+ # Integer-like levels
+ if lib.is_integer(level):
+ # Exclude bools (already handled above)
+ if level < 0 and level != -1:
  raise IndexError(
  "Too many levels: Index has only 1 level, "
  f"{level} is not a valid level number"
@@ -2107,21 +2111,15 @@ def _validate_index_level(self, level) -> None:
  raise IndexError(
  f"Too many levels: Index has only 1 level, not {level + 1}"
  )
+ return
 
- # String level: only match if name is exactly the same string
- elif isinstance(level, str) and not (
- isinstance(self.name, str) and level == self.name
- ):
+ # For all other types, require exact match to index name
+ # Use pandas' isna for both level and self.name to catch NA-like names
+ if isna(self.name) or level != self.name:
  raise KeyError(
  f"Requested level ({level}) does not match index name ({self.name})"
  )
 
- # If level type is not int, str, or is NA, always raise KeyError
- else:
- raise KeyError(
- f"Requested level ({level}) is not a valid level name or number"
- )
-
  def _get_level_number(self, level) -> int:
  self._validate_index_level(level)
  return 0