BUG: Enhance index level validation to handle NA-like index names and improve error messaging

Author: whyvineet

pandas/_libs/__init__.py

@@ -1,5 +1,4 @@
 __all__ = [
-    "NA",
     "Interval",
     "NaT",
     "NaTType",
@@ -17,7 +16,6 @@
 import pandas._libs.pandas_parser  # isort: skip # type: ignore[reportUnusedImport]
 import pandas._libs.pandas_datetime  # noqa: F401 # isort: skip # type: ignore[reportUnusedImport]
 from pandas._libs.interval import Interval
-from pandas._libs.missing import NA
 from pandas._libs.tslibs import (
     NaT,
     NaTType,

pandas/core/indexes/base.py

@@ -2091,6 +2091,12 @@ def _validate_index_level(self, level) -> None:
                 f"Requested level ({level}) does not match index name ({self.name})"
             )
 
+        # Handle NA-like index.name as well
+        if isna(self.name):
+            raise KeyError(
+                f"Requested level ({level}) does not match index name ({self.name})"
+            )
+
         # Reject booleans unless the index name is actually a boolean and matches
         if isinstance(level, bool):
             if level != self.name:
@@ -2102,20 +2108,24 @@ def _validate_index_level(self, level) -> None:
         # Integer-like levels
         if lib.is_integer(level):
             # Exclude bools (already handled above)
+            if isinstance(self.name, int) and level == self.name:
+                return
             if level < 0 and level != -1:
                 raise IndexError(
-                    "Too many levels: Index has only 1 level, "
-                    f"{level} is not a valid level number"
+                    "Too many levels: Index has only 1 level, not {}".format(level + 1)
                 )
-            if level > 0:
-                raise IndexError(
-                    f"Too many levels: Index has only 1 level, not {level + 1}"
+            return
+
+        # For string-level, require both to be strings and equal
+        if isinstance(level, str) and isinstance(self.name, str):
+            if level != self.name:
+                raise KeyError(
+                    f"Requested level ({level}) does not match index name ({self.name})"
                 )
             return
 
         # 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:
+        if level != self.name:
             raise KeyError(
                 f"Requested level ({level}) does not match index name ({self.name})"
             )