Copyable classes with bindable properties

Author: balex89

nicegui/binding.py

@@ -1,8 +1,9 @@
 import asyncio
+import copyreg
 import time
 from collections import defaultdict
 from collections.abc import Mapping
-from typing import Any, Callable, DefaultDict, Dict, Iterable, List, Optional, Set, Tuple, Union
+from typing import Any, Callable, DefaultDict, Dict, Iterable, List, Optional, Set, Tuple, Type, TypeVar, Union
 
 from . import core
 from .logging import log
@@ -11,8 +12,10 @@
 
 bindings: DefaultDict[Tuple[int, str], List] = defaultdict(list)
 bindable_properties: Dict[Tuple[int, str], Any] = {}
+copyable_classes: Set[Type] = set()
 active_links: List[Tuple[Any, str, Any, str, Callable[[Any], Any]]] = []
 
+T = TypeVar('T')
 
 def _has_attribute(obj: Union[object, Mapping], name: str) -> Any:
     if isinstance(obj, Mapping):
@@ -145,6 +148,8 @@ def __get__(self, owner: Any, _=None) -> Any:
 
     def __set__(self, owner: Any, value: Any) -> None:
         has_attr = hasattr(owner, '___' + self.name)
+        if not has_attr and type(owner) not in copyable_classes:
+            _make_copyable(type(owner))
         value_changed = has_attr and getattr(owner, '___' + self.name) != value
         if has_attr and not value_changed:
             return
@@ -187,3 +192,41 @@ def reset() -> None:
     bindings.clear()
     bindable_properties.clear()
     active_links.clear()
+
+
+def _register_bindables(original_obj: T, copy_obj: T) -> None:
+    """Ensure BindableProperties of an object copy are registered correctly.
+
+    :param original_obj: The object that was copied.
+    :param original_obj: The object copy.
+    """
+    for attr_name in dir(original_obj):
+        if (id(original_obj), attr_name) in bindable_properties:
+            bindable_properties[(id(copy_obj), attr_name)] = copy_obj
+
+
+def _register_bindables_pickle_function(obj: T) -> Tuple[Callable[..., T], Tuple[Any, ...]]:
+    """Construct the "reduce tuple" of an object with a wrapped pickle function, that registers bindable attributes"
+
+    :param obj: The object to be reduced.
+    """
+    reduced = obj.__reduce__()
+    if isinstance(reduced, str):
+        raise ValueError('Unexpected __reduce__() return type: str')
+    creator = reduced[0]
+
+    def creator_with_hook(*args, **kwargs) -> T:
+        obj_copy = creator(*args, **kwargs)
+        _register_bindables(obj, obj_copy)
+        return obj_copy
+
+    return (creator_with_hook,) + reduced[1:]
+
+
+def _make_copyable(cls: Type[T]) -> None:
+    """Modify the way `copy` module handles class instances so that `BindableProperty` attributes preserve bindability.
+
+    :param cls: The class to modify.
+    """
+    copyreg.pickle(cls, _register_bindables_pickle_function)
+    copyable_classes.add(cls)

tests/test_binding.py

@@ -1,8 +1,9 @@
+import copy
 from typing import Dict, Optional, Tuple
 
 from selenium.webdriver.common.keys import Keys
 
-from nicegui import ui
+from nicegui import binding, ui
 from nicegui.testing import Screen
 
 
@@ -105,3 +106,21 @@ def test_missing_target_attribute(screen: Screen):
 
     screen.open('/')
     screen.should_contain("text='Hello'")
+
+
+def test_copy_instance_with_bindable_property():
+    class TestClass:
+        x = binding.BindableProperty()
+        y = binding.BindableProperty()
+
+        def __init__(self):
+            self.x = 1
+            self.y = 2
+
+    original = TestClass()
+    duplicate = copy.copy(original)
+
+    assert (id(original), 'x') in binding.bindable_properties
+    assert (id(original), 'y') in binding.bindable_properties
+    assert (id(duplicate), 'x') in binding.bindable_properties
+    assert (id(duplicate), 'y') in binding.bindable_properties