From cab93bb8d4253b9ae0190425550fe83d0e2bd6b5 Mon Sep 17 00:00:00 2001
From: Vasilis Themelis <vdthemelis@gmail.com>
Date: Sat, 26 Aug 2023 16:14:24 +0100
Subject: [PATCH] Add `pass` to removed blocks of code

Solves #352 more generally.
---
 .gitignore                    |  1 +
 src/typeguard/_transformer.py | 21 ++++++++++++----
 tests/test_transformer.py     | 47 +++++++++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+), 5 deletions(-)

diff --git a/.gitignore b/.gitignore
index d66eb5ae..6d027d31 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 .idea
 .tox
 .coverage
+**/.coverage.*
 .cache
 .eggs/
 *.egg-info/
diff --git a/src/typeguard/_transformer.py b/src/typeguard/_transformer.py
index 24c723c3..541db56a 100644
--- a/src/typeguard/_transformer.py
+++ b/src/typeguard/_transformer.py
@@ -55,6 +55,7 @@
     copy_location,
     expr,
     fix_missing_locations,
+    iter_fields,
     keyword,
     walk,
 )
@@ -498,6 +499,21 @@ def __init__(
         self.target_node: FunctionDef | AsyncFunctionDef | None = None
         self.target_lineno = target_lineno
 
+    def generic_visit(self, node: AST) -> AST:
+        non_empty_list_fields = []
+        for field, val in iter_fields(node):
+            if isinstance(val, list) and len(val) > 0:
+                non_empty_list_fields.append(field)
+
+        node = super().generic_visit(node)
+
+        # Add `pass` to list fields that were optimised away
+        for field in non_empty_list_fields:
+            if not hasattr(node, field) or not getattr(node, field):
+                setattr(node, field, [Pass()])
+
+        return node
+
     @contextmanager
     def _use_memo(
         self, node: ClassDef | FunctionDef | AsyncFunctionDef
@@ -1175,11 +1191,6 @@ def visit_If(self, node: If) -> Any:
         """
         self.generic_visit(node)
 
-        # Fix empty node body (caused by removal of classes/functions not on the target
-        # path)
-        if not node.body:
-            node.body.append(Pass())
-
         if (
             self._memo is self._module_memo
             and isinstance(node.test, Name)
diff --git a/tests/test_transformer.py b/tests/test_transformer.py
index 67890cad..5c63d13e 100644
--- a/tests/test_transformer.py
+++ b/tests/test_transformer.py
@@ -1523,6 +1523,53 @@ def foo(x: str) -> None:
     )
 
 
+def test_dont_leave_empty_ast_container_nodes_2() -> None:
+    # Regression test for #352
+    node = parse(
+        dedent(
+            """
+            try:
+
+                class A:
+                    ...
+
+                def func():
+                    ...
+
+            except:
+
+                class A:
+                    ...
+
+                def func():
+                    ...
+
+
+            def foo(x: str) -> None:
+                pass
+            """
+        )
+    )
+    TypeguardTransformer(["foo"]).visit(node)
+    assert (
+        unparse(node)
+        == dedent(
+            """
+            try:
+                pass
+            except:
+                pass
+
+            def foo(x: str) -> None:
+                from typeguard import TypeCheckMemo
+                from typeguard._functions import check_argument_types
+                memo = TypeCheckMemo(globals(), locals())
+                check_argument_types('foo', {'x': (x, str)}, memo)
+            """
+        ).strip()
+    )
+
+
 def test_dont_parse_annotated_2nd_arg() -> None:
     # Regression test for #352
     node = parse(