`pass` statements are removed causing syntax errors

[Brad Luczywo]

Describe the bug A clear and concise description of what the bug is.
Under certain circumstances, pycln will remove pass statements, which can lead to syntax errors in code. As shown in the code snippet below, it has something to do with nested if statements and that conclude with else: pass.

I have trimmed the code down as much as possible to narrow in on the situations where this occurs. This does not appear to happen if there are not nested conditionals. Also, if there is not another assignment before the inner conditional, this also does not happen.

While this is example code, I am seeing this happening in production code.

To Reproduce Steps to reproduce the behavior:

1. Take this code snippet:

   import os
   
   
   def cleaner():
       if bool(True):
           no_thing = None
           if no_thing:
              pass
           else:
              pass
       else:
           pass

2. Run this Pycln command:

   $ pycln test_file.py

3. Unexpected fixed code (if present):
   Note: there are two empty lines preceding the cleaner() method that are hidden by Github

   def cleaner():
       if bool(True):
           no_thing = None
           if no_thing:
               pass
           else:
               pass
       else:

Expected behavior:

1. I expected the pass statement to not be removed by pycln unexpectedly.
2. Expected fixed code (if present):

def cleaner():
    if bool(True):
        no_thing = None
        if no_thing:
            pass
        else:
            pass
    else:
        pass

Environment (please complete the following information):

• Python Version: Python 3.9.6 and Python 3.10.1
• Pycln Version: v1.2.1
• OS Type: Linux, MacOS

[Brad Luczywo]

I found another situation where this happens, and it's an even simpler case. If a new Exception class is defined with a docstring and only pass in the body (which is a very common use case), pycln will remove the pass from the class.

Input file:

import os


class CleanError(Exception):
    """Save me!"""
    pass

Then run pycln test_error.py and the file now looks like this:

class CleanError(Exception):
    """Save me!"""

It isn't strictly a syntax error in this case, but it's still a little disconcerting to have pycln removing pass in various places, when that has seemingly nothing to do with cleaning imports.

[Hadi Alqattan]

Hi @BradLucky, I see your point, I've fixed this bug via PR #100.

Thanks a lot for being around and supporting the project.