REF: merge.py check for known arraylikes (pandas-dev#53041)

Author: jbrockmendel

pandas/core/reshape/merge.py

@@ -52,7 +52,6 @@
     ensure_float64,
     ensure_int64,
     ensure_object,
-    is_array_like,
     is_bool,
     is_bool_dtype,
     is_extension_array_dtype,
@@ -124,6 +123,8 @@
     np.object_: libhashtable.ObjectFactorizer,
 }
 
+_known = (np.ndarray, ExtensionArray, Index, ABCSeries)
+
 
 @Substitution("\nleft : DataFrame or named Series")
 @Appender(_merge_doc, indents=0)
@@ -928,7 +929,7 @@ def _maybe_add_join_keys(
         left_has_missing = None
         right_has_missing = None
 
-        assert all(is_array_like(x) for x in self.left_join_keys)
+        assert all(isinstance(x, _known) for x in self.left_join_keys)
 
         keys = zip(self.join_names, self.left_on, self.right_on)
         for i, (name, lname, rname) in enumerate(keys):
@@ -1141,8 +1142,8 @@ def _get_merge_keys(
 
         left, right = self.left, self.right
 
-        is_lkey = lambda x: is_array_like(x) and len(x) == len(left)
-        is_rkey = lambda x: is_array_like(x) and len(x) == len(right)
+        is_lkey = lambda x: isinstance(x, _known) and len(x) == len(left)
+        is_rkey = lambda x: isinstance(x, _known) and len(x) == len(right)
 
         # Note that pd.merge_asof() has separate 'on' and 'by' parameters. A
         # user could, for example, request 'left_index' and 'left_by'. In a
@@ -1914,7 +1915,7 @@ def _validate_left_right_on(self, left_on, right_on):
         # GH#29130 Check that merge keys do not have dtype object
         if not self.left_index:
             left_on_0 = left_on[0]
-            if is_array_like(left_on_0):
+            if isinstance(left_on_0, _known):
                 lo_dtype = left_on_0.dtype
             else:
                 lo_dtype = (
@@ -1927,7 +1928,7 @@ def _validate_left_right_on(self, left_on, right_on):
 
         if not self.right_index:
             right_on_0 = right_on[0]
-            if is_array_like(right_on_0):
+            if isinstance(right_on_0, _known):
                 ro_dtype = right_on_0.dtype
             else:
                 ro_dtype = (