Inject fields by metaclass and add test

evennia/contrib/base_systems/components/component.py

@@ -15,15 +15,14 @@ class BaseComponent(type):
     This is the metaclass for components,
     responsible for registering components to the listing.
     """
-
-    @classmethod
-    def __new__(cls, *args):
+    def __new__(cls, name, parents, attrs):
         """
         Every class that uses this metaclass will be registered
         as a component in the Component Listing using its name.
         All of them require a unique name.
         """
-        new_type = super().__new__(*args)
+        attrs['_fields'] = {}
+        new_type = super().__new__(cls, name, parents, attrs)
         if new_type.__base__ == object:
             return new_type
 
@@ -53,7 +52,7 @@ class Component(metaclass=BaseComponent):
     name = ""
     slot = None
 
-    _fields = {}
+    _fields: dict | None = None
 
     def __init__(self, host=None):
         assert self.name, "All Components must have a name"

evennia/contrib/base_systems/components/tests.py

@@ -85,6 +85,27 @@ class TestComponents(EvenniaTest):
         self.assertTrue(self.char1.test_a)
         self.assertTrue(self.char1.test_b)
 
+    def test_character_components_set_fields_properly(self):
+        test_a_fields = self.char1.test_a._fields
+        self.assertIn('my_int', test_a_fields)
+        self.assertIn('my_list', test_a_fields)
+        self.assertEqual(len(test_a_fields), 2)
+
+        test_b_fields = self.char1.test_b._fields
+        self.assertIn('my_int', test_b_fields)
+        self.assertIn('my_list', test_b_fields)
+        self.assertIn('default_tag', test_b_fields)
+        self.assertIn('single_tag', test_b_fields)
+        self.assertIn('multiple_tags', test_b_fields)
+        self.assertIn('default_single_tag', test_b_fields)
+        self.assertEqual(len(test_b_fields), 6)
+
+        test_ic_a_fields = self.char1.ic_a._fields
+        self.assertIn('my_int', test_ic_a_fields)
+        self.assertIn('my_list', test_ic_a_fields)
+        self.assertIn('my_other_int', test_ic_a_fields)
+        self.assertEqual(len(test_ic_a_fields), 3)
+
     def test_inherited_typeclass_does_not_include_child_class_components(self):
         char_with_c = create.create_object(
             InheritedTCWithComponents, key="char_with_c", location=self.room1, home=self.room1