fix: do not render slot tag when extracting fill tags (#786)

* fix: do not render slot tag when extracting fill tags

* refactor: show component path in error message

* docs: update changelog

* refactor: fix tests

CHANGELOG.md

@@ -1,5 +1,31 @@
 # Release notes
 
+## v0.114
+
+#### Fix
+
+- Prevent rendering Slot tags during fill discovery stage to fix a case when a component inside a slot
+  fill tried to access provided data too early.
+
+## v0.113
+
+#### Fix
+
+- Ensure consistent order of scripts in `Component.Media.js`
+
+## v0.112
+
+#### Fix
+
+- Allow components to accept default fill even if no default slot was encountered during rendering
+
+## v0.111
+
+#### Fix
+
+- Prevent rendering Component tags during fill discovery stage to fix a case when a component inside the default slot
+  tried to access provided data too early.
+
 ## 🚨📢 v0.110
 
 ### General

src/django_components/component.py

@@ -617,7 +617,31 @@ def _render(
         try:
             return self._render_impl(context, args, kwargs, slots, escape_slots_content, type, render_dependencies)
         except Exception as err:
-            raise _type(err)(f"An error occured while rendering component '{self.name}':\n{repr(err)}") from err
+            # Nicely format the error message to include the component path.
+            # E.g.
+            # ```
+            # KeyError: "An error occured while rendering components ProjectPage > ProjectLayoutTabbed >
+            # Layout > RenderContextProvider > Base > TabItem:
+            # Component 'TabItem' tried to inject a variable '_tab' before it was provided.
+            # ```
+
+            if not hasattr(err, "_components"):
+                err._components = []  # type: ignore[attr-defined]
+
+            components = getattr(err, "_components", [])
+
+            # Access the exception's message, see https://stackoverflow.com/a/75549200/9788634
+            if not components:
+                orig_msg = err.args[0]
+            else:
+                orig_msg = err.args[0].split("\n", 1)[1]
+
+            components.insert(0, self.name)
+            comp_path = " > ".join(components)
+            prefix = f"An error occured while rendering components {comp_path}:\n"
+
+            err.args = (prefix + orig_msg,)  # tuple of one
+            raise err
 
     def _render_impl(
         self,

src/django_components/slots.py

@@ -203,6 +203,12 @@ def __repr__(self) -> str:
     def render(self, context: Context) -> SafeString:
         trace_msg("RENDR", "SLOT", self.trace_id, self.node_id)
 
+        # Do not render `{% slot %}` tags within the `{% component %} .. {% endcomponent %}` tags
+        # at the fill discovery stage (when we render the component's body to determine if the body
+        # is a default slot, or contains named slots).
+        if _is_extracting_fill(context):
+            return ""
+
         if _COMPONENT_SLOT_CTX_CONTEXT_KEY not in context or not context[_COMPONENT_SLOT_CTX_CONTEXT_KEY]:
             raise TemplateSyntaxError(
                 "Encountered a SlotNode outside of a ComponentNode context. "

tests/test_component.py

@@ -318,6 +318,67 @@ def get_template(self, context):
             """,
         )
 
+    @parametrize_context_behavior(["django", "isolated"])
+    def test_prepends_exceptions_with_component_path(self):
+        @register("broken")
+        class Broken(Component):
+            template: types.django_html = """
+                {% load component_tags %}
+                <div> injected: {{ data|safe }} </div>
+                <main>
+                    {% slot "content" default / %}
+                </main>
+            """
+
+            def get_context_data(self):
+                data = self.inject("my_provide")
+                data["data1"]  # This should raise TypeError
+                return {"data": data}
+
+        @register("provider")
+        class Provider(Component):
+            def get_context_data(self, data: Any) -> Any:
+                return {"data": data}
+
+            template: types.django_html = """
+                {% load component_tags %}
+                {% provide "my_provide" key="hi" data=data %}
+                    {% slot "content" default / %}
+                {% endprovide %}
+            """
+
+        @register("parent")
+        class Parent(Component):
+            def get_context_data(self, data: Any) -> Any:
+                return {"data": data}
+
+            template: types.django_html = """
+                {% load component_tags %}
+                {% component "provider" data=data %}
+                    {% component "broken" %}
+                        {% slot "content" default / %}
+                    {% endcomponent %}
+                {% endcomponent %}
+            """
+
+        @register("root")
+        class Root(Component):
+            template: types.django_html = """
+                {% load component_tags %}
+                {% component "parent" data=123 %}
+                    {% fill "content" %}
+                        456
+                    {% endfill %}
+                {% endcomponent %}
+            """
+
+        with self.assertRaisesMessage(
+            TypeError,
+            "An error occured while rendering components Root > parent > provider > broken:\n"
+            "tuple indices must be integers or slices, not str",
+        ):
+            Root.render()
+
 
 class ComponentValidationTest(BaseTestCase):
     def test_validate_input_passes(self):

tests/test_templatetags_component.py

@@ -483,7 +483,7 @@ def test_raises_on_invalid_args(self):
         """
 
         template = Template(simple_tag_template)
-        with self.assertRaisesMessage(TypeError, "got an unexpected keyword argument \\'invalid_variable\\'"):
+        with self.assertRaisesMessage(TypeError, "got an unexpected keyword argument 'invalid_variable'"):
             template.render(Context({}))
 
 

tests/test_templatetags_provide.py

@@ -740,6 +740,7 @@ def get_context_data(self):
         with self.assertRaises(RuntimeError):
             comp.inject("abc", "def")
 
+    # See https://github.com/EmilStenstrom/django-components/pull/778
     @parametrize_context_behavior(["django", "isolated"])
     def test_inject_in_fill(self):
         @register("injectee")
@@ -804,3 +805,65 @@ class Root(Component):
             <main>456</main>
             """,
         )
+
+    # See https://github.com/EmilStenstrom/django-components/pull/786
+    @parametrize_context_behavior(["django", "isolated"])
+    def test_inject_in_slot_in_fill(self):
+        @register("injectee")
+        class Injectee(Component):
+            template: types.django_html = """
+                {% load component_tags %}
+                <div> injected: {{ data|safe }} </div>
+                <main>
+                    {% slot "content" default / %}
+                </main>
+            """
+
+            def get_context_data(self):
+                data = self.inject("my_provide")
+                return {"data": data}
+
+        @register("provider")
+        class Provider(Component):
+            def get_context_data(self, data: Any) -> Any:
+                return {"data": data}
+
+            template: types.django_html = """
+                {% load component_tags %}
+                {% provide "my_provide" key="hi" data=data %}
+                    {% slot "content" default / %}
+                {% endprovide %}
+            """
+
+        @register("parent")
+        class Parent(Component):
+            def get_context_data(self, data: Any) -> Any:
+                return {"data": data}
+
+            template: types.django_html = """
+                {% load component_tags %}
+                {% component "provider" data=data %}
+                    {% slot "content" default / %}
+                {% endcomponent %}
+            """
+
+        @register("root")
+        class Root(Component):
+            template: types.django_html = """
+                {% load component_tags %}
+                {% component "parent" data=123 %}
+                    {% component "injectee" / %}
+                {% endcomponent %}
+            """
+
+        rendered = Root.render()
+
+        self.assertHTMLEqual(
+            rendered,
+            """
+            <div>
+                injected: DepInject(key='hi', data=123)
+            </div>
+            <main></main>
+            """,
+        )