fix: KeyError on component_context_cache when slot rendered outside (#1210)

CHANGELOG.md

@@ -779,6 +779,8 @@ Summary:
 
 - Fix bug: Context processors data was being generated anew for each component. Now the data is correctly created once and reused across components with the same request ([#1165](https://github.com/django-components/django-components/issues/1165)).
 
+- Fix KeyError on `component_context_cache` when slots are rendered outside of the component's render context. ([#1189](https://github.com/django-components/django-components/issues/1189))
+
 ## v0.139.1
 
 #### Fix

src/django_components/component.py

@@ -2680,9 +2680,8 @@ class Component(metaclass=ComponentMeta):
             request = getattr(context, "request", None)
             # Check if this is a nested component and whether parent has request
             if request is None:
-                parent_id = context.get(_COMPONENT_CONTEXT_KEY, None)
-                if parent_id:
-                    parent_comp_ctx = component_context_cache[parent_id]
+                _, parent_comp_ctx = _get_parent_component_context(context)
+                if parent_comp_ctx:
                     request = parent_comp_ctx.request
 
         # Allow to provide no args/kwargs/slots/context
@@ -2736,13 +2735,11 @@ class Component(metaclass=ComponentMeta):
         # We pass down the components the info about the component's parent.
         # This is used for correctly resolving slot fills, correct rendering order,
         # or CSS scoping.
-        if context.get(_COMPONENT_CONTEXT_KEY, None):
-            parent_id = cast(str, context[_COMPONENT_CONTEXT_KEY])
-            parent_comp_ctx = component_context_cache[parent_id]
+        parent_id, parent_comp_ctx = _get_parent_component_context(context)
+        if parent_comp_ctx is not None:
             component_path = [*parent_comp_ctx.component_path, self.name]
             post_render_callbacks = parent_comp_ctx.post_render_callbacks
         else:
-            parent_id = None
             component_path = [self.name]
             post_render_callbacks = {}
 
@@ -3300,6 +3297,20 @@ class ComponentNode(BaseNode):
         return output
 
 
+def _get_parent_component_context(context: Context) -> Union[Tuple[None, None], Tuple[str, ComponentContext]]:
+    parent_id = context.get(_COMPONENT_CONTEXT_KEY, None)
+    if parent_id is None:
+        return None, None
+
+    # NOTE: This may happen when slots are rendered outside of the component's render context.
+    # See https://github.com/django-components/django-components/issues/1189
+    if parent_id not in component_context_cache:
+        return None, None
+
+    parent_comp_ctx = component_context_cache[parent_id]
+    return parent_id, parent_comp_ctx
+
+
 @contextmanager
 def _maybe_bind_template(context: Context, template: Template) -> Generator[None, Any, None]:
     if context.template is None:

tests/test_slots.py

@@ -474,3 +474,54 @@ class TestSlot:
             match=re.escape("Fill 'first' received content both through 'body' kwarg and '{% fill %}' body."),
         ):
             template.render(Context({"my_slot": my_slot}))
+
+    @djc_test(parametrize=PARAMETRIZE_CONTEXT_BEHAVIOR)
+    def test_slot_call_outside_render_context(self, components_settings):
+        from django_components import register, Component
+
+        seen_slots = []
+
+        @register("MyTopLevelComponent")
+        class MyTopLevelComponent(Component):
+            template = """
+                {% for thing in words %}
+                    {% component "MyComponentBeingLooped" / %}
+                {% endfor %}
+            """
+
+            def get_template_data(self, args, kwargs, slots, context):
+                return {
+                    "words": ["apple", "car", "russia"],
+                }
+
+        @register("MyComponentBeingLooped")
+        class MyComponentBeingLooped(Component):
+            template = """
+                {% component "MyComponentWithASlot" %}
+                    {% fill "my_slot" %}
+                        {% component "MyInnerComponent" / %}
+                    {% endfill %}
+                {% endcomponent %}
+            """
+
+        @register("MyInnerComponent")
+        class MyInnerComponent(Component):
+            template = "Hello!"
+
+        @register("MyComponentWithASlot")
+        class MyComponentWithASlot(Component):
+            template = "CAPTURER"
+
+            def get_template_data(self, args, kwargs, slots, context):
+                seen_slots.append(self.input.slots["my_slot"])
+
+        MyTopLevelComponent.render()
+
+        assert len(seen_slots) == 3
+
+        results = [slot().strip() for slot in seen_slots]
+        assert results == [
+            "<!-- _RENDERED MyInnerComponent_fb676b,ca1bc49,, -->Hello!",
+            "<!-- _RENDERED MyInnerComponent_fb676b,ca1bc4a,, -->Hello!",
+            "<!-- _RENDERED MyInnerComponent_fb676b,ca1bc4b,, -->Hello!",
+        ]