BUG: Appending string to column returns in different order

[pyrito]

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): macOS 12.2.1
• Modin version (modin.__version__): 0.15.0+101.g14edd1ca
• Python version: 3.9.12
• Code we can use to reproduce:

import modin.pandas as pd
import pandas
from modin.pandas.test.utils import df_equals

pdf = pandas.DataFrame({'a' : ['a','b','c','d']})
mdf = pd.DataFrame({'a' : ['a','b','c','d']})

pdf['a'] = 'random_string' + pdf['a']
mdf['a'] = 'random_string' + mdf['a']

df_equals(pdf, mdf)

Describe the problem

Appending a string to a str column in a Modin DataFrame returns values in a different order.

Source code / logs

Error logs

---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
Input In [18], in <cell line: 11>()
      8 pdf['a'] = 'random_string' + pdf['a']
      9 mdf['a'] = 'random_string' + mdf['a']
---> 11 df_equals(pdf, mdf)

File ~/Documents/modin/modin/pandas/test/utils.py:589, in df_equals(df1, df2)
    586     assert_empty_frame_equal(df1, df2)
    588 if isinstance(df1, pandas.DataFrame) and isinstance(df2, pandas.DataFrame):
--> 589     assert_frame_equal(
    590         df1,
    591         df2,
    592         check_dtype=False,
    593         check_datetimelike_compat=True,
    594         check_index_type=False,
    595         check_column_type=False,
    596         check_categorical=False,
    597     )
    598     df_categories_equals(df1, df2)
    599 elif isinstance(df1, pandas.Index) and isinstance(df2, pandas.Index):

    [... skipping hidden 2 frame]

File ~/opt/anaconda3/envs/modin/lib/python3.9/site-packages/pandas/_libs/testing.pyx:52, in pandas._libs.testing.assert_almost_equal()

File ~/opt/anaconda3/envs/modin/lib/python3.9/site-packages/pandas/_libs/testing.pyx:167, in pandas._libs.testing.assert_almost_equal()

File ~/opt/anaconda3/envs/modin/lib/python3.9/site-packages/pandas/_testing/asserters.py:682, in raise_assert_detail(obj, message, left, right, diff, index_values)
    679 if diff is not None:
    680     msg += f"\n[diff]: {diff}"
--> 682 raise AssertionError(msg)

AssertionError: DataFrame.iloc[:, 0] (column name="a") are different

DataFrame.iloc[:, 0] (column name="a") values are different (100.0 %)
[index]: [0, 1, 2, 3]
[left]:  [random_stringa, random_stringb, random_stringc, random_stringd]
[right]: [arandom_string, brandom_string, crandom_string, drandom_string]

[pyrito]

The problem here is that radd is just an alias for add so we don't actually consider the position of arguments. We'll have to make some changes to handle this case.