From 24859641affe04cc358adba47ea8ba447350263b Mon Sep 17 00:00:00 2001
From: Korijn van Golen <k.vangolen@clinicalgraphics.com>
Date: Fri, 5 Jan 2024 14:43:07 +0100
Subject: [PATCH] support magic methods

---
 observ/object_proxy.py     | 152 ++++++++++++++++++++++++++++++++++++-
 tests/test_object_proxy.py |   8 ++
 tests/test_usage.py        |  33 ++++++++
 3 files changed, 192 insertions(+), 1 deletion(-)

diff --git a/observ/object_proxy.py b/observ/object_proxy.py
index 4acaee4..0d240b7 100644
--- a/observ/object_proxy.py
+++ b/observ/object_proxy.py
@@ -7,7 +7,7 @@
 from .traps import ReadonlyError
 
 
-class ObjectProxy(Proxy):
+class ObjectProxyBase(Proxy):
     def __getattribute__(self, name):
         if name in Proxy.__slots__:
             return super().__getattribute__(name)
@@ -86,6 +86,156 @@ def __delattr__(self, name):
         return retval
 
 
+def passthrough(method):
+    def trap(self, *args, **kwargs):
+        fn = getattr(self.__target__, method, None)
+        if fn is None:
+            raise TypeError(f"object of type '{type(self)}' has no {method}")
+        return fn(*args, **kwargs)
+
+    return trap
+
+
+magic_methods = [
+    "__abs__",
+    "__add__",
+    "__aenter__",
+    "__aexit__",
+    "__aiter__",
+    "__and__",
+    "__anext__",
+    "__annotations__",
+    "__await__",
+    "__bases__",
+    "__bool__",
+    "__buffer__",
+    "__bytes__",
+    "__call__",
+    "__ceil__",
+    "__class__",
+    "__class_getitem__",
+    # '__classcell__',
+    "__closure__",
+    "__code__",
+    "__complex__",
+    "__contains__",
+    "__defaults__",
+    # '__del__',
+    # '__delattr__',
+    "__delete__",
+    "__delitem__",
+    "__dict__",
+    "__dir__",
+    "__divmod__",
+    "__doc__",
+    "__enter__",
+    "__eq__",
+    "__exit__",
+    "__file__",
+    "__float__",
+    "__floor__",
+    "__floordiv__",
+    "__format__",
+    "__func__",
+    "__future__",
+    "__ge__",
+    "__get__",
+    # "__getattr__",
+    # '__getattribute__',
+    "__getitem__",
+    "__globals__",
+    "__gt__",
+    "__hash__",
+    "__iadd__",
+    "__iand__",
+    "__ifloordiv__",
+    "__ilshift__",
+    "__imatmul__",
+    "__imod__",
+    "__import__",
+    "__imul__",
+    "__index__",
+    # '__init__',
+    "__init_subclass__",
+    "__instancecheck__",
+    "__int__",
+    "__invert__",
+    "__ior__",
+    "__ipow__",
+    "__irshift__",
+    "__isub__",
+    "__iter__",
+    "__itruediv__",
+    "__ixor__",
+    "__kwdefaults__",
+    "__le__",
+    "__len__",
+    "__length_hint__",
+    "__lshift__",
+    "__lt__",
+    "__match_args__",
+    "__matmul__",
+    "__missing__",
+    "__mod__",
+    "__module__",
+    "__mro__",
+    "__mro_entries__",
+    "__mul__",
+    "__name__",
+    "__ne__",
+    "__neg__",
+    # '__new__',
+    "__next__",
+    "__objclass__",
+    "__or__",
+    "__pos__",
+    "__pow__",
+    "__prepare__",
+    # '__qualname__',
+    "__radd__",
+    "__rand__",
+    "__rdivmod__",
+    "__release_buffer__",
+    "__repr__",
+    "__reversed__",
+    "__rfloordiv__",
+    "__rlshift__",
+    "__rmatmul__",
+    "__rmod__",
+    "__rmul__",
+    "__ror__",
+    "__round__",
+    "__rpow__",
+    "__rrshift__",
+    "__rshift__",
+    "__rsub__",
+    "__rtruediv__",
+    "__rxor__",
+    "__self__",
+    "__set__",
+    "__set_name__",
+    # '__setattr__',
+    "__setitem__",
+    # '__slots__',
+    "__str__",
+    "__sub__",
+    "__subclasscheck__",
+    "__traceback__",
+    "__truediv__",
+    "__trunc__",
+    "__type_params__",
+    "__weakref__",
+    "__xor__",
+]
+
+
+ObjectProxy = type(
+    "ObjectProxy",
+    (ObjectProxyBase,),
+    {method: passthrough(method) for method in magic_methods},
+)
+
+
 class ReadonlyObjectProxy(ObjectProxy):
     def __init__(self, target, shallow=False, **kwargs):
         super().__init__(target, shallow=shallow, **{**kwargs, "readonly": True})
diff --git a/tests/test_object_proxy.py b/tests/test_object_proxy.py
index f71c28b..c67724a 100644
--- a/tests/test_object_proxy.py
+++ b/tests/test_object_proxy.py
@@ -75,3 +75,11 @@ def test_readonly_proxy():
 
     another_proxied.bar = 25
     assert proxied.bar == 25
+
+    with pytest.raises(ReadonlyError):
+        delattr(readonly_proxy, "baz")
+    delattr(another_proxied, "baz")
+
+    assert not hasattr(proxied, "baz")
+
+
diff --git a/tests/test_usage.py b/tests/test_usage.py
index 8e6cff4..14aae14 100644
--- a/tests/test_usage.py
+++ b/tests/test_usage.py
@@ -1,3 +1,4 @@
+from dataclasses import dataclass
 from typing import Iterable
 from unittest.mock import Mock
 
@@ -596,6 +597,9 @@ def test_usage_class_instances():
     class Foo:
         def __init__(self):
             self.foo = 5
+        
+        def __len__(self):
+            return self.foo
 
     a = reactive([1, 2, Foo()])
     called = 0
@@ -621,6 +625,35 @@ def _callback():
     a[2].foo = 10
     assert called == 3
 
+    # magic methods are supported
+    foo_len = computed(lambda: len(a[2]))
+    assert foo_len() == 10
+
+
+def test_usage_dataclass():
+    @dataclass
+    class Foo:
+        bar: int
+
+    a = reactive(Foo(bar=5))
+    called = 0
+
+    def _callback():
+        nonlocal called
+        called += 1
+
+    watcher = watch(lambda: a, _callback, sync=True, deep=True)
+    assert not watcher.dirty
+    assert called == 0
+
+    # write something
+    a.bar = 10
+    assert called == 1
+
+    # magic methods are supported
+    str_foo = computed(lambda: repr(a))
+    assert str_foo() == "test_usage_dataclass.<locals>.Foo(bar=10)"
+
 
 def test_watch_get_non_existing():
     a = reactive({})