Add metaclass capable of building instances from class name string

tfw/internals/event_handling/type_id_registry/__init__.py

@@ -0,0 +1 @@
+from .type_id_registry import TypeIdREgistryMixin

tfw/internals/event_handling/type_id_registry/test_type_id_registry.py

@@ -0,0 +1,43 @@
+import pytest
+
+from .type_id_registry import TypeIdREgistryMixin
+
+
+def test_registry():
+    class A(TypeIdREgistryMixin):
+        _type_id_registry = {}
+    class B(A):
+        pass
+    class C(A):
+        pass
+
+    # pylint: disable=protected-access
+    assert A._type_id_registry['B'] == B
+    assert A._type_id_registry['C'] == C
+
+
+def test_build_by_type_id():
+    class D(TypeIdREgistryMixin):
+        _type_id_registry = {}
+    built = []
+    class E(D):
+        def __init__(self):
+            built.append(self)
+    class F(D):
+        def __init__(self):
+            built.append(self)
+            raise RuntimeError('cica')
+    class H(E):
+        pass
+
+    D.build_type('E')
+    assert isinstance(built[0], E)
+
+    with pytest.raises(RuntimeError) as err:
+        D.build_type('F')
+    assert err.value.args[0] == 'cica'
+    assert isinstance(built[1], F)
+
+    D.build_type('H')
+    assert isinstance(built[2], H)
+    assert isinstance(built[2], E)

tfw/internals/event_handling/type_id_registry/type_id_registry.py

@@ -0,0 +1,21 @@
+from abc import ABCMeta
+from contextlib import suppress
+
+
+class TypeIdREgistryMeta(ABCMeta):
+    def __init__(cls, name, bases, attrs):
+        with suppress(AttributeError):
+            if cls.__name__ in cls._type_id_registry:
+                raise RuntimeError('Type id must be unique!')
+            cls._type_id_registry[cls.__name__] = cls
+        super().__init__(name, bases, attrs)
+
+
+class TypeIdREgistryMixin(metaclass=TypeIdREgistryMeta):
+    @classmethod
+    def build_type(cls, type_id, *args, **kwargs):
+        try:
+            instance_type = cls._type_id_registry[type_id]
+            return instance_type(*args, **kwargs)
+        except KeyError:
+            raise RuntimeError(f'No type with id {type_id}!')