feat: allow to set defaults (#1072)

* feat: allow to set defaults

* docs: update changelog

* refactor: fix new linter errors

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