feat: allow to set defaults (#1072)

* feat: allow to set defaults

* docs: update changelog

* refactor: fix new linter errors

CHANGELOG.md

@@ -4,6 +4,39 @@
 
 #### Feat
 
+- Add defaults for the component inputs with the `Component.Defaults` nested class. Defaults
+  are applied if the argument is not given, or if it set to `None`.
+  
+  For lists, dictionaries, or other objects, wrap the value in `Default()` class to mark it as a factory
+  function:
+
+    ```python
+    from django_components import Default
+
+    class Table(Component):
+        class Defaults:
+            position = "left"
+            width = "200px"
+            options = Default(lambda: ["left", "right", "center"])
+
+        def get_context_data(self, position, width, options):
+            return {
+                "position": position,
+                "width": width,
+                "options": options,
+            }
+
+    # `position` is used as given, `"right"`
+    # `width` uses default because it's `None`
+    # `options` uses default because it's missing
+    Table.render(
+        kwargs={
+            "position": "right",
+            "width": None,
+        }
+    )
+    ```
+
 - `{% html_attrs %}` now offers a Vue-like granular control over `class` and `style` HTML attributes,
 where each class name or style property can be managed separately.
 

benchmarks/benchmark_templating.py

@@ -140,7 +140,6 @@ def prepare_templating_benchmark(
     context_mode: DjcContextMode,
     imports_only: bool = False,
 ):
-    global do_render
     setup_script = _get_templating_script(renderer, size, context_mode, imports_only)
 
     # If we're testing the startup time, then the setup is actually the tested code

docs/concepts/fundamentals/.nav.yml

@@ -3,6 +3,7 @@ nav:
   - Single-file components: single_file_components.md
   - Components in Python: components_in_python.md
   - Accessing component inputs: access_component_input.md
+  - Component defaults: component_defaults.md
   - Component context and scope: component_context_scope.md
   - Template tag syntax: template_tag_syntax.md
   - Slots: slots.md

docs/concepts/fundamentals/component_defaults.md

@@ -0,0 +1,133 @@
+When a component is being rendered, the component inputs are passed to various methods like
+[`get_context_data()`](../../../reference/api#django_components.Component.get_context_data),
+[`get_js_data()`](../../../reference/api#django_components.Component.get_js_data),
+or [`get_css_data()`](../../../reference/api#django_components.Component.get_css_data).
+
+It can be cumbersome to specify default values for each input in each method.
+
+To make things easier, Components can specify their defaults. Defaults are used when
+no value is provided, or when the value is set to `None` for a particular input.
+
+### Defining defaults
+
+To define defaults for a component, you create a nested `Defaults` class within your
+[`Component`](../../../reference/api#django_components.Component) class.
+Each attribute in the `Defaults` class represents a default value for a corresponding input.
+
+```py
+from django_components import Component, Default, register
+
+@register("my_table")
+class MyTable(Component):
+
+    class Defaults:
+        position = "left"
+        selected_items = Default(lambda: [1, 2, 3])
+
+    def get_context_data(self, position, selected_items):
+        return {
+            "position": position,
+            "selected_items": selected_items,
+        }
+
+    ...
+```
+
+In this example, `position` is a simple default value, while `selected_items` uses a factory function wrapped in `Default` to ensure a new list is created each time the default is used.
+
+Now, when we render the component, the defaults will be applied:
+
+```django
+{% component "my_table" position="right" / %}
+```
+
+In this case:
+
+- `position` input is set to `right`, so no defaults applied
+- `selected_items` is not set, so it will be set to `[1, 2, 3]`.
+
+Same applies to rendering the Component in Python with the
+[`render()`](../../../reference/api#django_components.Component.render) method:
+
+```py
+MyTable.render(
+    kwargs={
+        "position": "right",
+        "selected_items": None,
+    },
+)
+```
+
+Notice that we've set `selected_items` to `None`. `None` values are treated as missing values,
+and so `selected_items` will be set to `[1, 2, 3]`.
+
+!!! warning
+
+    The defaults are aplied only to keyword arguments. They are NOT applied to positional arguments!
+
+### Default factories
+
+For objects such as lists, dictionaries or other instances, you have to be careful - if you simply set a default value, this instance will be shared across all instances of the component!
+
+```py
+from django_components import Component
+
+class MyTable(Component):
+    class Defaults:
+        # All instances will share the same list!
+        selected_items = [1, 2, 3]
+```
+
+To avoid this, you can use a factory function wrapped in `Default`.
+
+```py
+from django_components import Component, Default
+
+class MyTable(Component):
+    class Defaults:
+        # A new list is created for each instance
+        selected_items = Default(lambda: [1, 2, 3])
+```
+
+This is similar to how the dataclass fields work.
+
+In fact, you can also use the dataclass's [`field`](https://docs.python.org/3/library/dataclasses.html#dataclasses.field) function to define the factories:
+
+```py
+from dataclasses import field
+from django_components import Component
+
+class MyTable(Component):
+    class Defaults:
+        selected_items = field(default_factory=lambda: [1, 2, 3])
+```
+
+### Accessing defaults
+
+Since the defaults are defined on the component class, you can access the defaults for a component with the `Component.Defaults` property.
+
+So if we have a component like this:
+
+```py
+from django_components import Component, Default, register
+
+@register("my_table")
+class MyTable(Component):
+
+    class Defaults:
+        position = "left"
+        selected_items = Default(lambda: [1, 2, 3])
+
+    def get_context_data(self, position, selected_items):
+        return {
+            "position": position,
+            "selected_items": selected_items,
+        }
+```
+
+We can access individual defaults like this:
+
+```py
+print(MyTable.Defaults.position)
+print(MyTable.Defaults.selected_items)
+```

docs/getting_started/parametrising_components.md

@@ -68,7 +68,7 @@ from django_components import Component, register
 class Calendar(Component):
     template_file = "calendar.html"
     ...
-    def get_context_data(self, date: date, extra_class: str | None = None):
+    def get_context_data(self, date: date, extra_class: str = "text-blue"):
         return {
             "date": date,
             "extra_class": extra_class,
@@ -197,7 +197,7 @@ def to_workweek_date(d: date):
 class Calendar(Component):
     template_file = "calendar.html"
     ...
-    def get_context_data(self, date: date, extra_class: str | None = None):
+    def get_context_data(self, date: date, extra_class: str = "text-blue"):
         workweek_date = to_workweek_date(date)  # <--- new
         return {
             "date": workweek_date,  # <--- changed
@@ -220,3 +220,38 @@ the parametrized version of the component:
 ---
 
 Next, you will learn [how to use slots give your components even more flexibility ➡️](./adding_slots.md)
+
+### 5. Add defaults
+
+In our example, we've set the `extra_class` to default to `"text-blue"` by setting it in the
+[`get_context_data()`](../../reference/api#django_components.Component.get_context_data)
+method.
+
+However, you may want to use the same default value in multiple methods, like
+[`get_js_data()`](../../reference/api#django_components.Component.get_js_data)
+or [`get_css_data()`](../../reference/api#django_components.Component.get_css_data).
+
+To make things easier, Components can specify their defaults. Defaults are used when
+no value is provided, or when the value is set to `None` for a particular input.
+
+To define defaults for a component, you create a nested `Defaults` class within your
+[`Component`](../../reference/api#django_components.Component) class.
+Each attribute in the `Defaults` class represents a default value for a corresponding input.
+
+```py
+from django_components import Component, Default, register
+
+@register("calendar")
+class Calendar(Component):
+    template_file = "calendar.html"
+
+    class Defaults:  # <--- new
+        extra_class = "text-blue"
+
+    def get_context_data(self, date: date, extra_class: str):  # <--- changed
+        workweek_date = to_workweek_date(date)
+        return {
+            "date": workweek_date,
+            "extra_class": extra_class,
+        }
+```

docs/reference/api.md

@@ -75,6 +75,10 @@
     options:
       show_if_no_docstring: true
 
+::: django_components.Default
+    options:
+      show_if_no_docstring: true
+
 ::: django_components.EmptyDict
     options:
       show_if_no_docstring: true

docs/reference/template_tags.md

@@ -67,7 +67,7 @@ If you insert this tag multiple times, ALL JS scripts will be duplicately insert
 
 
 
-<a href="https://github.com/django-components/django-components/tree/master/src/django_components/templatetags/component_tags.py#L1584" target="_blank">See source code</a>
+<a href="https://github.com/django-components/django-components/tree/master/src/django_components/templatetags/component_tags.py#L1494" target="_blank">See source code</a>
 
 
 

src/django_components/__init__.py

@@ -40,6 +40,7 @@ from django_components.extension import (
     OnComponentInputContext,
     OnComponentDataContext,
 )
+from django_components.extensions.defaults import Default
 from django_components.extensions.view import ComponentView
 from django_components.library import TagProtectedError
 from django_components.node import BaseNode, template_tag
@@ -88,6 +89,7 @@ __all__ = [
     "component_formatter",
     "component_shorthand_formatter",
     "ContextBehavior",
+    "Default",
     "DynamicComponent",
     "EmptyTuple",
     "EmptyDict",

src/django_components/app_settings.py

@@ -750,9 +750,10 @@ class InternalSettings:
         )
 
         # Prepend built-in extensions
+        from django_components.extensions.defaults import DefaultsExtension
         from django_components.extensions.view import ViewExtension
 
-        extensions = [ViewExtension] + list(extensions)
+        extensions = [DefaultsExtension, ViewExtension] + list(extensions)
 
         # Extensions may be passed in either as classes or import strings.
         extension_instances: List["ComponentExtension"] = []

src/django_components/component.py

@@ -962,6 +962,8 @@ class Component(
             - `"document"` (default) - JS dependencies are inserted into `{% component_js_dependencies %}`,
               or to the end of the `<body>` tag. CSS dependencies are inserted into
               `{% component_css_dependencies %}`, or the end of the `<head>` tag.
+            - `"fragment"` - `{% component_js_dependencies %}` and `{% component_css_dependencies %}`,
+              are ignored, and a script that loads the JS and CSS dependencies is appended to the HTML.
         - `request` - The request object. This is only required when needing to use RequestContext,
                       e.g. to enable template `context_processors`.
 
@@ -1030,6 +1032,8 @@ class Component(
             - `"document"` (default) - JS dependencies are inserted into `{% component_js_dependencies %}`,
               or to the end of the `<body>` tag. CSS dependencies are inserted into
               `{% component_css_dependencies %}`, or the end of the `<head>` tag.
+            - `"fragment"` - `{% component_js_dependencies %}` and `{% component_css_dependencies %}`,
+              are ignored, and a script that loads the JS and CSS dependencies is appended to the HTML.
         - `render_dependencies` - Set this to `False` if you want to insert the resulting HTML into another component.
         - `request` - The request object. This is only required when needing to use RequestContext,
                       e.g. to enable template `context_processors`.
@@ -1107,9 +1111,14 @@ class Component(
                     request = parent_comp_ctx.request
 
         # Allow to provide no args/kwargs/slots/context
-        args = cast(ArgsType, args or ())
-        kwargs = cast(KwargsType, kwargs or {})
-        slots_untyped = self._normalize_slot_fills(slots or {}, escape_slots_content)
+        # NOTE: We make copies of args / kwargs / slots, so that plugins can modify them
+        # without affecting the original values.
+        args = cast(ArgsType, list(args) if args is not None else ())
+        kwargs = cast(KwargsType, dict(kwargs) if kwargs is not None else {})
+        slots_untyped = self._normalize_slot_fills(
+            dict(slots) if slots is not None else {},
+            escape_slots_content,
+        )
         slots = cast(SlotsType, slots_untyped)
         # Use RequestContext if request is provided, so that child non-component template tags
         # can access the request object too.

src/django_components/extensions/defaults.py

@@ -0,0 +1,157 @@
+import sys
+from dataclasses import MISSING, Field, dataclass
+from typing import TYPE_CHECKING, Any, Callable, Dict, List, NamedTuple, Optional, Type
+from weakref import WeakKeyDictionary
+
+from django_components.extension import ComponentExtension, OnComponentClassCreatedContext, OnComponentInputContext
+
+if TYPE_CHECKING:
+    from django_components.component import Component
+
+
+# NOTE: `WeakKeyDictionary` is NOT a generic pre-3.9
+if sys.version_info >= (3, 9):
+    ComponentDefaultsCache = WeakKeyDictionary[Type["Component"], List["ComponentDefaultField"]]
+else:
+    ComponentDefaultsCache = WeakKeyDictionary
+
+
+defaults_by_component: ComponentDefaultsCache = WeakKeyDictionary()
+
+
+@dataclass
+class Default:
+    """
+    Use this class to mark a field on the `Component.Defaults` class as a factory.
+
+    Read more about [Component defaults](../../concepts/fundamentals/component_defaults).
+
+    **Example:**
+
+    ```py
+    from django_components import Default
+
+    class MyComponent(Component):
+        class Defaults:
+            # Plain value doesn't need a factory
+            position = "left"
+            # Lists and dicts need to be wrapped in `Default`
+            # Otherwise all instances will share the same value
+            selected_items = Default(lambda: [1, 2, 3])
+    ```
+    """
+
+    value: Callable[[], Any]
+
+
+class ComponentDefaultField(NamedTuple):
+    """Internal representation of a field on the `Defaults` class."""
+
+    key: str
+    value: Any
+    is_factory: bool
+
+
+# Figure out which defaults are factories and which are not, at class creation,
+# so that the actual creation of the defaults dictionary is simple.
+def _extract_defaults(defaults: Optional[Type]) -> List[ComponentDefaultField]:
+    defaults_fields: List[ComponentDefaultField] = []
+    if defaults is None:
+        return defaults_fields
+
+    for default_field_key in dir(defaults):
+        # Iterate only over fields set by the user (so non-dunder fields).
+        # Plus ignore `component_class` because that was set by the extension system.
+        if default_field_key.startswith("__") or default_field_key == "component_class":
+            continue
+
+        default_field = getattr(defaults, default_field_key)
+
+        # If the field was defined with dataclass.field(), take the default / factory from there.
+        if isinstance(default_field, Field):
+            if default_field.default is not MISSING:
+                field_value = default_field.default
+                is_factory = False
+            elif default_field.default_factory is not MISSING:
+                field_value = default_field.default_factory
+                is_factory = True
+            else:
+                field_value = None
+                is_factory = False
+
+        # If the field was defined with our `Default` class, it defined a factory
+        elif isinstance(default_field, Default):
+            field_value = default_field.value
+            is_factory = True
+
+        # If the field was defined with a simple assignment, assume it's NOT a factory.
+        else:
+            field_value = default_field
+            is_factory = False
+
+        field_data = ComponentDefaultField(
+            key=default_field_key,
+            value=field_value,
+            is_factory=is_factory,
+        )
+        defaults_fields.append(field_data)
+
+    return defaults_fields
+
+
+def _apply_defaults(kwargs: Dict, defaults: List[ComponentDefaultField]) -> None:
+    """
+    Apply the defaults from `Component.Defaults` to the given `kwargs`.
+
+    Defaults are applied only to missing or `None` values.
+    """
+    for default_field in defaults:
+        # Defaults are applied only to missing or `None` values
+        given_value = kwargs.get(default_field.key, None)
+        if given_value is not None:
+            continue
+
+        if default_field.is_factory:
+            default_value = default_field.value()
+        else:
+            default_value = default_field.value
+
+        kwargs[default_field.key] = default_value
+
+
+class DefaultsExtension(ComponentExtension):
+    """
+    This extension adds a nested `Defaults` class to each `Component`.
+
+    This nested `Defaults` class is used to set default values for the component's kwargs.
+
+    **Example:**
+
+    ```py
+    from django_components import Component, Default
+
+    class MyComponent(Component):
+        class Defaults:
+            position = "left"
+            # Factory values need to be wrapped in `Default`
+            selected_items = Default(lambda: [1, 2, 3])
+    ```
+
+    This extension is automatically added to all components.
+    """
+
+    name = "defaults"
+
+    # Preprocess the `Component.Defaults` class, if given, so we don't have to do it
+    # each time a component is rendered.
+    def on_component_class_created(self, ctx: OnComponentClassCreatedContext) -> None:
+        defaults_cls = getattr(ctx.component_cls, "Defaults", None)
+        defaults_by_component[ctx.component_cls] = _extract_defaults(defaults_cls)
+
+    # Apply defaults to missing or `None` values in `kwargs`
+    def on_component_input(self, ctx: OnComponentInputContext) -> None:
+        defaults = defaults_by_component.get(ctx.component_cls, None)
+        if defaults is None:
+            return
+
+        _apply_defaults(ctx.kwargs, defaults)

src/django_components/util/tag_parser.py

@@ -447,7 +447,6 @@ def parse_tag(text: str, parser: Optional[Parser]) -> Tuple[str, List[TagAttr]]:
         return False
 
     def taken_n(n: int) -> str:
-        nonlocal index
         result = text[index : index + n]  # noqa: E203
         add_token(result)
         return result
@@ -457,9 +456,6 @@ def parse_tag(text: str, parser: Optional[Parser]) -> Tuple[str, List[TagAttr]]:
         tokens: Union[List[str], Tuple[str, ...]],
         ignore: Optional[Sequence[str]] = None,
     ) -> str:
-        nonlocal index
-        nonlocal text
-
         result = ""
         while not is_at_end():
             char = text[index]
@@ -483,9 +479,6 @@ def parse_tag(text: str, parser: Optional[Parser]) -> Tuple[str, List[TagAttr]]:
 
     # tag_name = take_while([" ", "\t", "\n", "\r", "\f"])
     def take_while(tokens: Union[List[str], Tuple[str, ...]]) -> str:
-        nonlocal index
-        nonlocal text
-
         result = ""
         while not is_at_end():
             char = text[index]

tests/test_command_ext.py

@@ -97,7 +97,7 @@ class TestExtensionsListCommand:
             call_command("components", "ext", "list")
         output = out.getvalue()
 
-        assert output.strip() == "name\n====\nview"
+        assert output.strip() == "name    \n========\ndefaults\nview"
 
     @djc_test(
         components_settings={"extensions": [EmptyExtension, DummyExtension]},
@@ -108,7 +108,7 @@ class TestExtensionsListCommand:
             call_command("components", "ext", "list")
         output = out.getvalue()
 
-        assert output.strip() == "name \n=====\nview \nempty\ndummy"
+        assert output.strip() == "name    \n========\ndefaults\nview    \nempty   \ndummy"
 
     @djc_test(
         components_settings={"extensions": [EmptyExtension, DummyExtension]},
@@ -119,7 +119,7 @@ class TestExtensionsListCommand:
             call_command("components", "ext", "list", "--all")
         output = out.getvalue()
 
-        assert output.strip() == "name \n=====\nview \nempty\ndummy"
+        assert output.strip() == "name    \n========\ndefaults\nview    \nempty   \ndummy"
 
     @djc_test(
         components_settings={"extensions": [EmptyExtension, DummyExtension]},
@@ -130,7 +130,7 @@ class TestExtensionsListCommand:
             call_command("components", "ext", "list", "--columns", "name")
         output = out.getvalue()
 
-        assert output.strip() == "name \n=====\nview \nempty\ndummy"
+        assert output.strip() == "name    \n========\ndefaults\nview    \nempty   \ndummy"
 
     @djc_test(
         components_settings={"extensions": [EmptyExtension, DummyExtension]},
@@ -141,7 +141,7 @@ class TestExtensionsListCommand:
             call_command("components", "ext", "list", "--simple")
         output = out.getvalue()
 
-        assert output.strip() == "view \nempty\ndummy"
+        assert output.strip() == "defaults\nview    \nempty   \ndummy"
 
 
 @djc_test
@@ -159,18 +159,19 @@ class TestExtensionsRunCommand:
             output
             == dedent(
                 f"""
-                usage: components ext run [-h] {{view,empty,dummy}} ...
+                usage: components ext run [-h] {{defaults,view,empty,dummy}} ...
 
                 Run a command added by an extension.
 
                 {OPTIONS_TITLE}:
-                  -h, --help          show this help message and exit
+                  -h, --help            show this help message and exit
 
                 subcommands:
-                  {{view,empty,dummy}}
-                    view              Run commands added by the 'view' extension.
-                    empty             Run commands added by the 'empty' extension.
-                    dummy             Run commands added by the 'dummy' extension.
+                  {{defaults,view,empty,dummy}}
+                    defaults            Run commands added by the 'defaults' extension.
+                    view                Run commands added by the 'view' extension.
+                    empty               Run commands added by the 'empty' extension.
+                    dummy               Run commands added by the 'dummy' extension.
                 """
             ).lstrip()
         )

tests/test_component.py

@@ -293,7 +293,7 @@ class TestComponent:
         class TestComponent(Component):
             @no_type_check
             def get_context_data(self, var1, var2, variable, another, **attrs):
-                assert self.input.args == (123, "str")
+                assert self.input.args == [123, "str"]
                 assert self.input.kwargs == {"variable": "test", "another": 1}
                 assert isinstance(self.input.context, Context)
                 assert list(self.input.slots.keys()) == ["my_slot"]
@@ -305,7 +305,7 @@ class TestComponent:
 
             @no_type_check
             def get_template(self, context):
-                assert self.input.args == (123, "str")
+                assert self.input.args == [123, "str"]
                 assert self.input.kwargs == {"variable": "test", "another": 1}
                 assert isinstance(self.input.context, Context)
                 assert list(self.input.slots.keys()) == ["my_slot"]

tests/test_component_defaults.py

@@ -0,0 +1,147 @@
+from dataclasses import field
+from typing import Any
+
+from django.template import Context
+
+from django_components import Component, Default
+
+from django_components.testing import djc_test
+from .testutils import setup_test_config
+
+setup_test_config({"autodiscover": False})
+
+
+@djc_test
+class TestComponentDefaults:
+    def test_input_defaults(self):
+        did_call_context = False
+
+        class TestComponent(Component):
+            template = ""
+
+            class Defaults:
+                variable = "test"
+                another = 1
+                extra = "extra"
+                fn = lambda: "fn_as_val"  # noqa: E731
+
+            def get_context_data(self, arg1: Any, variable: Any, another: Any, **attrs: Any):
+                nonlocal did_call_context
+                did_call_context = True
+
+                # Check that args and slots are NOT affected by the defaults
+                assert self.input.args == [123]
+                assert [*self.input.slots.keys()] == ["my_slot"]
+                assert self.input.slots["my_slot"](Context(), None, None) == "MY_SLOT"
+
+                assert self.input.kwargs == {
+                    "variable": "test",  # User-given
+                    "another": 1,  # Default because missing
+                    "extra": "extra",  # Default because `None` was given
+                    "fn": self.Defaults.fn,  # Default because missing
+                }
+                assert isinstance(self.input.context, Context)
+
+                return {
+                    "variable": variable,
+                }
+
+        TestComponent.render(
+            args=(123,),
+            kwargs={"variable": "test", "extra": None},
+            slots={"my_slot": "MY_SLOT"},
+        )
+
+        assert did_call_context
+
+    def test_factory_from_class(self):
+        did_call_context = False
+
+        class TestComponent(Component):
+            template = ""
+
+            class Defaults:
+                variable = "test"
+                fn = Default(lambda: "fn_as_factory")
+
+            def get_context_data(self, variable: Any, **attrs: Any):
+                nonlocal did_call_context
+                did_call_context = True
+
+                assert self.input.kwargs == {
+                    "variable": "test",  # User-given
+                    "fn": "fn_as_factory",  # Default because missing
+                }
+                assert isinstance(self.input.context, Context)
+
+                return {
+                    "variable": variable,
+                }
+
+        TestComponent.render(
+            kwargs={"variable": "test"},
+        )
+
+        assert did_call_context
+
+    def test_factory_from_dataclass_field_value(self):
+        did_call_context = False
+
+        class TestComponent(Component):
+            template = ""
+
+            class Defaults:
+                variable = "test"
+                fn = field(default=lambda: "fn_as_factory")
+
+            def get_context_data(self, variable: Any, **attrs: Any):
+                nonlocal did_call_context
+                did_call_context = True
+
+                assert self.input.kwargs == {
+                    "variable": "test",  # User-given
+                    # NOTE: NOT a factory, because it was set as `field(default=...)`
+                    "fn": self.Defaults.fn.default,  # type: ignore[attr-defined]
+                }
+                assert isinstance(self.input.context, Context)
+
+                return {
+                    "variable": variable,
+                }
+
+        TestComponent.render(
+            kwargs={"variable": "test"},
+        )
+
+        assert did_call_context
+
+    def test_factory_from_dataclass_field_factory(self):
+        did_call_context = False
+
+        class TestComponent(Component):
+            template = ""
+
+            class Defaults:
+                variable = "test"
+                fn = field(default_factory=lambda: "fn_as_factory")
+
+            def get_context_data(self, variable: Any, **attrs: Any):
+                nonlocal did_call_context
+                did_call_context = True
+
+                assert self.input.kwargs == {
+                    "variable": "test",  # User-given
+                    # NOTE: IS a factory, because it was set as `field(default_factory=...)`
+                    "fn": "fn_as_factory",  # Default because missing
+                }
+                assert isinstance(self.input.context, Context)
+
+                return {
+                    "variable": variable,
+                }
+
+        TestComponent.render(
+            kwargs={"variable": "test"},
+        )
+
+        assert did_call_context

tests/test_extension.py

@@ -20,6 +20,7 @@ from django_components.extension import (
     OnComponentInputContext,
     OnComponentDataContext,
 )
+from django_components.extensions.defaults import DefaultsExtension
 from django_components.extensions.view import ViewExtension
 
 from django_components.testing import djc_test
@@ -125,9 +126,10 @@ def with_registry(on_created: Callable):
 class TestExtension:
     @djc_test(components_settings={"extensions": [DummyExtension]})
     def test_extensions_setting(self):
-        assert len(app_settings.EXTENSIONS) == 2
-        assert isinstance(app_settings.EXTENSIONS[0], ViewExtension)
-        assert isinstance(app_settings.EXTENSIONS[1], DummyExtension)
+        assert len(app_settings.EXTENSIONS) == 3
+        assert isinstance(app_settings.EXTENSIONS[0], DefaultsExtension)
+        assert isinstance(app_settings.EXTENSIONS[1], ViewExtension)
+        assert isinstance(app_settings.EXTENSIONS[2], DummyExtension)
 
     @djc_test(components_settings={"extensions": [DummyExtension]})
     def test_access_component_from_extension(self):
@@ -150,7 +152,7 @@ class TestExtension:
 class TestExtensionHooks:
     @djc_test(components_settings={"extensions": [DummyExtension]})
     def test_component_class_lifecycle_hooks(self):
-        extension = cast(DummyExtension, app_settings.EXTENSIONS[1])
+        extension = cast(DummyExtension, app_settings.EXTENSIONS[2])
 
         assert len(extension.calls["on_component_class_created"]) == 0
         assert len(extension.calls["on_component_class_deleted"]) == 0
@@ -182,7 +184,7 @@ class TestExtensionHooks:
 
     @djc_test(components_settings={"extensions": [DummyExtension]})
     def test_registry_lifecycle_hooks(self):
-        extension = cast(DummyExtension, app_settings.EXTENSIONS[1])
+        extension = cast(DummyExtension, app_settings.EXTENSIONS[2])
 
         assert len(extension.calls["on_registry_created"]) == 0
         assert len(extension.calls["on_registry_deleted"]) == 0
@@ -219,7 +221,7 @@ class TestExtensionHooks:
                 return {"name": name}
 
         registry.register("test_comp", TestComponent)
-        extension = cast(DummyExtension, app_settings.EXTENSIONS[1])
+        extension = cast(DummyExtension, app_settings.EXTENSIONS[2])
 
         # Verify on_component_registered was called
         assert len(extension.calls["on_component_registered"]) == 1
@@ -257,14 +259,14 @@ class TestExtensionHooks:
         test_slots = {"content": "Some content"}
         TestComponent.render(context=test_context, args=("arg1", "arg2"), kwargs={"name": "Test"}, slots=test_slots)
 
-        extension = cast(DummyExtension, app_settings.EXTENSIONS[1])
+        extension = cast(DummyExtension, app_settings.EXTENSIONS[2])
 
         # Verify on_component_input was called with correct args
         assert len(extension.calls["on_component_input"]) == 1
         input_call: OnComponentInputContext = extension.calls["on_component_input"][0]
         assert input_call.component_cls == TestComponent
         assert isinstance(input_call.component_id, str)
-        assert input_call.args == ("arg1", "arg2")
+        assert input_call.args == ["arg1", "arg2"]
         assert input_call.kwargs == {"name": "Test"}
         assert len(input_call.slots) == 1
         assert isinstance(input_call.slots["content"], Slot)