CHANGELOG

@@ -20,3 +20,11 @@
 ## Patch Updates
 * restricts the callable exclusion so that attributes set with callables still
 show up(resolves #5)
+
+# 0.4.0 - frozen speedup
+## Major Updates
+* sped up frozen attribute setting (resolves #6)
+  * requires FrozenMixin users to use the new `self._thaw()` context manager
+  in `__init__` in order to set attributes, where before you could just set
+  them.  If this change isn't made, AttributeErrors will start to be raised at
+  init time for FrozenMixin classes.

din.py

@@ -2,6 +2,7 @@
 
 
 # [ Imports:Python ]
+import contextlib
 import copy
 import inspect
 import typing
@@ -304,12 +305,21 @@ class FrozenMixin:
     say foo.my_string = 'new thing', but you can do foo.my_list.append('new thing').
     """
 
-    def __setattr__(self, name: str, value: typing.Any) -> None:
-        # if the caller is self.__init__, make the update
+    @contextlib.contextmanager
+    def _thawed(self) -> typing.Iterator:
         stack = inspect.stack()
-        caller = stack[1].frame.f_locals.get('self', None)
-        func = stack[1].function
-        if caller is self and func == '__init__':
+        caller = stack[2].frame.f_locals.get('self', None)
+        func = stack[2].function
+        if not (caller is self and func == '__init__'):
+            raise RuntimeError("Can only thaw from __init__!")
+        object.__setattr__(self, '__is_thawed', True)
+        try:
+            yield
+        finally:
+            object.__setattr__(self, '__is_thawed', False)
+
+    def __setattr__(self, name: str, value: typing.Any) -> None:
+        if getattr(self, '__is_thawed', False):
             object.__setattr__(self, name, value)
             return
         # else, don't

test.py

@@ -797,7 +797,8 @@ def test_independent_reprs() -> None:
 class _FrozenTestObject(din.FrozenMixin):
     def __init__(self) -> None:
         super().__init__()
-        self.my_string = 'original'
+        with self._thawed():
+            self.my_string = 'original'
 
 
 def test_frozen() -> None:
@@ -835,3 +836,58 @@ def test_copy_frozen() -> None:
     assert frozen.my_string == 'original'
     # the new object has the new value
     assert frozen_2.my_string == 'changed!'
+
+
+def test_frozen_inheritance() -> None:
+    # Given
+    # a frozen object
+    class _Inherited(_FrozenTestObject):
+        def __init__(self) -> None:
+            super().__init__()
+            with self._thawed():
+                self.additional_thing = "set in init"
+
+    frozen = _Inherited()
+    # an expected error
+    expected_message = "Can't set additional_thing, because _Inherited is frozen."
+
+    # When
+    # an attribute is set
+    try:
+        frozen.additional_thing = 'changed!'
+    except AttributeError as error:
+        actual_message = str(error)
+
+    # Then
+    # an attribute error is raised
+    assert expected_message == actual_message
+    # the value didn't change
+    assert frozen.my_string == 'original'
+    # vulture
+    frozen.additional_thing  # pylint: disable=pointless-statement
+
+
+def test_frozen_bad_thaw() -> None:
+    # Given
+    # a frozen object
+    class _Inherited(_FrozenTestObject):
+        def update(self) -> None:
+            with self._thawed():
+                self.my_string = "updated"
+
+    frozen = _Inherited()
+    # an expected error
+    expected_message = "Can only thaw from __init__!"
+
+    # When
+    # an attribute is set
+    try:
+        frozen.update()
+    except RuntimeError as error:
+        actual_message = str(error)
+
+    # Then
+    # an attribute error is raised
+    assert expected_message == actual_message
+    # the value didn't change
+    assert frozen.my_string == 'original'

version.py

@@ -2,7 +2,7 @@
 
 
 # [ API ]
-VERSION = '0.3.2'
+VERSION = '0.4.0'
 
 
 # [ Vulture ]