Improve item class getting

docs/CHANGELOG.rst

@@ -3,6 +3,11 @@ Version history
 
 We follow `Semantic Versions <https://semver.org/>`_.
 
+0.8.2 (29.11.24)
+*******************************************************************************
+- Add ability to specify ``TypeAlias`` as ``_item class`` and use
+  ``ListComponent`` as a parameterized type
+
 0.8.1 (25.11.24)
 *******************************************************************************
 - Improve getting ``item class`` from first ``ListComponent`` generic variable.

pomcorn/component.py

@@ -1,3 +1,4 @@
+import typing
 from inspect import isclass
 from typing import (
     Any,
@@ -207,6 +208,43 @@ class ListComponent(Generic[ListItemType, TPage], Component[TPage]):
     item_locator: locators.XPathLocator | None = None
     relative_item_locator: locators.XPathLocator | None = None
 
+    def __class_getitem__(cls, item: tuple[type, ...]) -> Any:
+        """Create parameterized versions of generic classes.
+
+        This method is called when the class is used as a parameterized type,
+        such as MyGeneric[int] or MyGeneric[List[str]].
+
+        We override this method to store values passed in generic parameters.
+
+        Args:
+            cls - The generic class itself.
+            item - The type used for parameterization.
+
+        Returns:
+            type: A parameterized version of the class with the specified type.
+
+        """
+        list_cls = super().__class_getitem__(item)  # type: ignore
+        cls.__parameters__ = item  # type: ignore
+        return list_cls
+
+    def __init__(
+        self,
+        page: TPage,
+        base_locator: locators.XPathLocator | None = None,
+        wait_until_visible: bool = True,
+    ) -> None:
+        # If `_item_class` was not specified in `__init_subclass__`, this means
+        # that `ListComponent` is used as a parameterized type
+        # (e.g., `List[ItemClass, Page]`).
+        if isinstance(self._item_class, _EmptyValue):
+            # In this way we check the stored generic parameters and, if first
+            # from them is valid, set it as `_item_class`
+            first_generic_param = self.__parameters__[0]
+            if self.is_valid_item_class(first_generic_param):
+                self._item_class = first_generic_param
+        super().__init__(page, base_locator, wait_until_visible)
+
     def __init_subclass__(cls) -> None:
         """Run logic for getting/overriding item_class attr for subclasses."""
         super().__init_subclass__()
@@ -297,10 +335,19 @@ def get_list_item_class(cls) -> type[ListItemType] | None:
     def is_valid_item_class(cls, item_class: Any) -> bool:
         """Check that specified ``item_class`` is valid.
 
-        Valid `item_class` should be a class and subclass of ``Component``.
+        Valid ``item_class`` should be
+        * a class and subclass of ``Component``
+        * or TypeAlias based on ``Component``
 
         """
-        return isclass(item_class) and issubclass(item_class, Component)
+        if isclass(item_class) and issubclass(item_class, Component):
+            return True
+
+        if isinstance(item_class, typing._GenericAlias):  # type: ignore
+            type_alias = item_class.__origin__  # type: ignore
+            return isclass(type_alias) and issubclass(type_alias, Component)
+
+        return False
 
     def get_item_by_text(self, text: str) -> ListItemType:
         """Get list item by text."""

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "pomcorn"
-version = "0.8.1"
+version = "0.8.2"
 description = "Base implementation of Page Object Model"
 authors = [
   "Saritasa <[email protected]>",

tests/list_component/test_item_class.py

@@ -1,4 +1,4 @@
-from typing import Generic, TypeVar
+from typing import Generic, TypeAlias, TypeVar
 
 import pytest
 
@@ -105,3 +105,34 @@ class List(BaseList[Param]):
     # Ensure that `List.item_class` has correct type
     list_cls = List(fake_page)
     assert list_cls._item_class is ItemClass
+
+
+def test_set_item_class_without_inheritance(fake_page: Page) -> None:
+    """Check that item_class will be correct in not inherited class."""
+
+    class BaseList(Generic[TItem, TPage], ListComponent[TItem, TPage]):
+        """Base list component without specified Generic variables."""
+
+        base_locator = locators.XPathLocator("html")  # required
+        relative_item_locator = locators.XPathLocator("body")  # required
+        wait_until_visible = lambda _: True  # to not wait anything
+
+    # Prepare base list component without specified Generic variables
+    list_cls = BaseList[ItemClass, Page](fake_page)
+    # Ensure that `InheritedList.item_class` has correct type
+    assert list_cls._item_class is ItemClass
+
+
+# Type alias for check that ItemClass can be also a TypeAlias
+TypeAliasItemClass: TypeAlias = Component[Page]
+
+
+def test_item_class_can_be_type_alias(fake_page: Page) -> None:
+    """Check that item_class can be a type alias based on ``Component``."""
+
+    class List(ListComponent[TypeAliasItemClass, Page]):
+        base_locator = locators.XPathLocator("html")  # required
+        wait_until_visible = lambda _: True  # to not wait anything
+
+    list_cls = List(fake_page)
+    assert list_cls._item_class is TypeAliasItemClass