# Buggy code
def _maybe_add_join_keys(self, result, left_indexer, right_indexer):
    left_has_missing = None
    right_has_missing = None

    keys = zip(self.join_names, self.left_on, self.right_on)
    for i, (name, lname, rname) in enumerate(keys):
        if not _should_fill(lname, rname):
            continue

        take_left, take_right = None, None

        if name in result:
            if left_indexer is not None and right_indexer is not None:
                if name in self.left:
                    if left_has_missing is None:
                        left_has_missing = (left_indexer == -1).any()

                    if left_has_missing:
                        take_right = self.right_join_keys[i]

                        if not is_dtype_equal(
                            result[name].dtype, self.left[name].dtype
                        ):
                            take_left = self.left[name]._values

                elif name in self.right:
                    if right_has_missing is None:
                        right_has_missing = (right_indexer == -1).any()

                    if right_has_missing:
                        take_left = self.left_join_keys[i]

                        if not is_dtype_equal(
                            result[name].dtype, self.right[name].dtype
                        ):
                            take_right = self.right[name]._values

        elif left_indexer is not None and is_array_like(self.left_join_keys[i]):
            take_left = self.left_join_keys[i]
            take_right = self.right_join_keys[i]

        if take_left is not None or take_right is not None:
            if take_left is None:
                lvals = result[name]._values
            else:
                lfill = na_value_for_dtype(take_left.dtype)
                lvals = algos.take_1d(take_left, left_indexer, fill_value=lfill)

            if take_right is None:
                rvals = result[name]._values
            else:
                rfill = na_value_for_dtype(take_right.dtype)
                rvals = algos.take_1d(take_right, right_indexer, fill_value=rfill)

            # if we have an all missing left_indexer
            # make sure to just use the right values or vice-versa
            mask_left = left_indexer == -1
            mask_right = right_indexer == -1
            if mask_left.all():
                key_col = rvals
            elif right_indexer is not None and mask_right.all():
                key_col = lvals
            else:
                key_col = Index(lvals).where(~mask_left, rvals)

            if result._is_label_reference(name):
                result[name] = key_col
            elif result._is_level_reference(name):
                if isinstance(result.index, MultiIndex):
                    key_col.name = name
                    idx_list = [
                        result.index.get_level_values(level_name)
                        if level_name != name
                        else key_col
                        for level_name in result.index.names
                    ]

                    result.set_index(idx_list, inplace=True)
                else:
                    result.index = Index(key_col, name=name)
            else:
                result.insert(i, name or f"key_{i}", key_col)


# Traceback (AttributeError)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.8/site-packages/pandas/core/reshape/merge.py", line 88, in merge
return op.get_result()
File "/usr/lib/python3.8/site-packages/pandas/core/reshape/merge.py", line 668, in get_result
self._maybe_add_join_keys(result, left_indexer, right_indexer)
File "/usr/lib/python3.8/site-packages/pandas/core/reshape/merge.py", line 824, in _maybe_add_join_keys
key_col.name = name
AttributeError: 'numpy.ndarray' object has no attribute 'name'

# Fixed code
def _maybe_add_join_keys(self, result, left_indexer, right_indexer):
    left_has_missing = None
    right_has_missing = None

    keys = zip(self.join_names, self.left_on, self.right_on)
    for i, (name, lname, rname) in enumerate(keys):
        if not _should_fill(lname, rname):
            continue

        take_left, take_right = None, None

        if name in result:
            if left_indexer is not None and right_indexer is not None:
                if name in self.left:
                    if left_has_missing is None:
                        left_has_missing = (left_indexer == -1).any()

                    if left_has_missing:
                        take_right = self.right_join_keys[i]

                        if not is_dtype_equal(
                            result[name].dtype, self.left[name].dtype
                        ):
                            take_left = self.left[name]._values

                elif name in self.right:
                    if right_has_missing is None:
                        right_has_missing = (right_indexer == -1).any()

                    if right_has_missing:
                        take_left = self.left_join_keys[i]

                        if not is_dtype_equal(
                            result[name].dtype, self.right[name].dtype
                        ):
                            take_right = self.right[name]._values

        elif left_indexer is not None and is_array_like(self.left_join_keys[i]):
            take_left = self.left_join_keys[i]
            take_right = self.right_join_keys[i]

        if take_left is not None or take_right is not None:
            if take_left is None:
                lvals = result[name]._values
            else:
                lfill = na_value_for_dtype(take_left.dtype)
                lvals = algos.take_1d(take_left, left_indexer, fill_value=lfill)

            if take_right is None:
                rvals = result[name]._values
            else:
                rfill = na_value_for_dtype(take_right.dtype)
                rvals = algos.take_1d(take_right, right_indexer, fill_value=rfill)

            # if we have an all missing left_indexer
            # make sure to just use the right values or vice-versa
            mask_left = left_indexer == -1
            mask_right = right_indexer == -1
            if mask_left.all():
                key_col = Index(rvals)
            elif right_indexer is not None and mask_right.all():
                key_col = Index(lvals)
            else:
                key_col = Index(lvals).where(~mask_left, rvals)

            if result._is_label_reference(name):
                result[name] = key_col
            elif result._is_level_reference(name):
                if isinstance(result.index, MultiIndex):
                    key_col.name = name
                    idx_list = [
                        result.index.get_level_values(level_name)
                        if level_name != name
                        else key_col
                        for level_name in result.index.names
                    ]

                    result.set_index(idx_list, inplace=True)
                else:
                    result.index = Index(key_col, name=name)
            else:
                result.insert(i, name or f"key_{i}", key_col)