Fix: pass statements are removed causing syntax errors. (#100)

* Fix: pass statements are removed causing syntax errors.

* Add: changelog

docs/CHANGELOG.md

@@ -10,6 +10,14 @@ this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Fixed
+
+- [`pass` statements are removed from `orelse` parent nodes causing syntax errors by @hadialqattan](https://github.com/hadialqattan/pycln/pull/100)
+
+### Changed
+
+- [In case of `(async)func`/`class` contains docstring, keep only one `pass` statement instead of none by @hadialqattan](https://github.com/hadialqattan/pycln/pull/100)
+
 ## [1.2.1] - 2022-02-24
 
 ### Fixed

pycln/utils/refactor.py

@@ -4,7 +4,7 @@
 from functools import lru_cache
 from importlib import import_module
 from pathlib import Path
-from typing import List, Optional, Set, Tuple, Union, cast
+from typing import Iterable, List, Optional, Set, Tuple, Union, cast
 
 from . import iou, pathu, regexu, scan
 from ._exceptions import (
@@ -84,16 +84,48 @@ def remove_useless_passes(source_lines: List[str]) -> List[str]:
         :param source_lines: source code lines.
         :returns: clean source code lines.
         """
+
+        def remove_from_children(
+            parent: ast.AST, children: Iterable, body_len: int, wl: Set[ast.AST]
+        ):
+            #: Remove any `ast.Pass` node
+            #: that is both useless and not in the `wl` (white list).
+            #:
+            #: The below case is not going to be touched:
+            #:
+            #: >>> (async) (def) (class) foo:
+            #: >>>      """DOCString"""
+            #: >>>      pass
+            #:
+            for child in children:
+                if isinstance(child, ast.Pass):
+                    if child not in wl:
+                        if isinstance(
+                            parent,
+                            (ast.AsyncFunctionDef, ast.FunctionDef, ast.ClassDef),
+                        ):
+                            if body_len == 2 and ast.get_docstring(parent):
+                                break
+                        if body_len > 1:
+                            body_len -= 1
+                            source_lines[child.lineno - 1] = ""
+
         tree = ast.parse("".join(source_lines))
         for parent in ast.walk(tree):
+
             body = getattr(parent, "body", None)
             if body and hasattr(body, "__len__"):
                 body_len = len(body)
-            for child in ast.iter_child_nodes(parent):
-                if isinstance(child, ast.Pass):
-                    if body_len > 1:
-                        body_len -= 1
-                        source_lines[child.lineno - 1] = ""
+                white_list: Set[ast.AST] = set()
+
+                if hasattr(parent, "orelse"):
+                    orelse = getattr(parent, "orelse")
+                    remove_from_children(parent, orelse, len(orelse), white_list)
+                    white_list = set(orelse)
+
+                children = ast.iter_child_nodes(parent)
+                remove_from_children(parent, children, body_len, white_list)
+
         return "".join(source_lines).splitlines(True)
 
     def session(self, path: Path) -> None:

tests/test_refactor.py

@@ -113,15 +113,31 @@ def setup_method(self, method):
             ),
             pytest.param(
                 [
+                    "class Foo:\n",
+                    "    '''docs'''\n",
+                    "    pass\n",
+                    "    pass\n",
+                    "async def foo():\n",
+                    "    '''docs'''\n",
+                    "    pass\n",
+                    "    pass\n",
                     "def foo():\n",
                     "    '''docs'''\n",
                     "    pass\n",
+                    "    pass\n",
                 ],
                 [
+                    "class Foo:\n",
+                    "    '''docs'''\n",
+                    "    pass\n",
+                    "async def foo():\n",
+                    "    '''docs'''\n",
+                    "    pass\n",
                     "def foo():\n",
                     "    '''docs'''\n",
+                    "    pass\n",
                 ],
-                id="useless with docs",
+                id="useless with docstring",
             ),
             pytest.param(
                 [
@@ -132,6 +148,52 @@ def setup_method(self, method):
                 ],
                 id="TypeError",
             ),
+            pytest.param(
+                [
+                    "if True:\n",
+                    "   pass\n",
+                    "   pass\n",
+                    "else:\n",
+                    "   pass\n",
+                    "   pass\n",
+                ],
+                [
+                    "if True:\n",
+                    "   pass\n",
+                    "else:\n",
+                    "   pass\n",
+                ],
+                id="orelse parent - else - useless",
+            ),
+            pytest.param(
+                [
+                    "if True:\n",
+                    "   print()\n",
+                    "   print()\n",
+                    "else:\n",
+                    "   pass\n",
+                ],
+                [
+                    "if True:\n",
+                    "   print()\n",
+                    "   print()\n",
+                    "else:\n",
+                    "   pass\n",
+                ],
+                id="orelse parent - else - useful",
+            ),
+            pytest.param(
+                [
+                    "if True:\n",
+                    "   print()\n",
+                    "   pass\n",
+                ],
+                [
+                    "if True:\n",
+                    "   print()\n",
+                ],
+                id="orelse parent - no-else",
+            ),
         ],
     )
     def test_remove_useless_passes(self, source_lines, expec_lines):