Add test for child recursion error.

adamghill · adamghill · commit 3333811b10f0 · 2026-01-10T23:13:43.000-05:00
diff --git a/src/django_unicorn/components/unicorn_template_response.py b/src/django_unicorn/components/unicorn_template_response.py
@@ -248,11 +248,13 @@ def render(self):
                     for child in descendant.children:
                         init_script = f"{init_script} {child._init_script}"
                         json_tags.append(child._json_tag)
+
                         # We need to delete this property here as it can cause RecursionError
                         # when pickling child component. Tag element has previous_sibling
                         # and next_sibling which would also be pickled and if they are big,
                         # cause RecursionError
                         del child._json_tag
+
                         descendants.append(child)
 
                 script_tag = soup.new_tag("script")
diff --git a/tests/components/test_unicorn_template_response_recursion.py b/tests/components/test_unicorn_template_response_recursion.py
@@ -0,0 +1,63 @@
+import pickle
+import sys
+from unittest.mock import MagicMock
+
+from bs4 import BeautifulSoup
+from django.test import RequestFactory
+
+from django_unicorn.components import UnicornView
+from django_unicorn.components.unicorn_template_response import UnicornTemplateResponse
+
+
+class RecursionComponent(UnicornView):
+    template_name = "templates/test_component.html"
+    pass
+
+
+def test_child_component_cleanup_prevents_recursion_error():
+    # 1. Create child component and simulate it having a large _json_tag (as if rendered)
+    child = RecursionComponent(component_name="child", component_id="child_id")
+
+    # Create a deep DOM to ensure recursion error would happen if not cleaned up
+    depth = 2000
+    html_content = "<div>" + ("<span>" * depth) + "Hello" + ("</span>" * depth) + "</div>"
+    soup = BeautifulSoup(html_content, "html.parser")
+    child._json_tag = soup.find("div")  # Simulate the tag attached during child render
+    child._init_script = "Unicorn.componentInit({});"
+
+    # 2. Create parent component and link child
+    parent = RecursionComponent(component_name="parent", component_id="parent_id")
+    parent.children.append(child)
+
+    # 3. Setup UnicornTemplateResponse for parent
+    request = RequestFactory().get("/")
+    template = MagicMock()
+    template.render.return_value = "<html><body><div unicorn:view>Parent Content</div></body></html>"
+
+    response = UnicornTemplateResponse(
+        template=template,
+        request=request,
+        component=parent,
+        init_js=True,  # Important to trigger the logic that collects json_tags
+    )
+
+    # Increase recursion limit to allow BS4 to process the deep tree without crashing during render
+    # We want to verify that pickling works AFTER the tag is removed, not that BS4 crashes.
+    original_recursion_limit = sys.getrecursionlimit()
+    sys.setrecursionlimit(10000)
+
+    try:
+        # 4. Render the parent
+        # This should trigger the loop that collects children's json_tags and DELETES them
+        response.render()
+
+        # 5. Verify _json_tag is deleted from child
+        assert not hasattr(child, "_json_tag"), "child._json_tag should have been deleted"
+
+        # 6. Verify pickling parent works
+        # If _json_tag was arguably still there, this might fail or pass depending on limit.
+        # But since we verified it IS deleted, this confirms the object state is clean.
+        pickle.dumps(parent)
+
+    finally:
+        sys.setrecursionlimit(original_recursion_limit)
