Allow subclassing from missing dependency

generalimport/fake_module.py

@@ -1,5 +1,7 @@
 from typing import Optional
 import sys
+from functools import partialmethod
+from generalimport import MissingOptionalDependency
 from generalimport.exception import MissingOptionalDependency, MissingDependencyException
 
 
@@ -43,6 +45,22 @@ def __getattr__(self, item):
             fakemodule.error_func()
         return FakeModule(spec=self.__spec__, trigger=item)
 
+    def __mro_entries__(self, *a, **k):
+        """
+        This prevents the creation of subclasses from triggering `generalimport`.
+
+        The classes so generated will trigger generalimport as soon as they're instantiated.
+        """
+        class FakeBaseClass:
+
+            def __new__(fake_cls, *args, **kwargs):
+                self.error_func("__new__")
+
+            def __init__(fake_self, *args, **kwargs):
+                self.error_func("__init__")
+
+        return (FakeBaseClass, )
+
     # Binary
     __ilshift__ = __invert__ = __irshift__ = __ixor__ = __lshift__ = __rlshift__ = __rrshift__ = __rshift__ = error_func
 

generalimport/test/test_usage/test_object.py

@@ -1,26 +1,48 @@
-import sys
-from unittest import skip
-
-import generalimport as gi
 from generalimport import *
 
 from generalimport.test.funcs import ImportTestCase
 
 
 class Test(ImportTestCase):
-    def test_init_subclass(self):
-        """ This one is caught by __call__. """
+    def test_subclass_class_returning_self(self):
         generalimport("fakepackage")
         import fakepackage
 
+        class SubClass(fakepackage.BaseClass):
+            pass
+
+        foo = SubClass.bar  # Won't error if SubClass is a FakeModule
+
         with self.assertRaises(MissingDependencyException):
-            class X(fakepackage):
-                pass
+            foo *= 2
+
+    def test_subclass_module(self):
+        generalimport("fakepackage")
+        import fakepackage
 
+        class X(fakepackage):
+            pass
 
+        with self.assertRaises(MissingDependencyException):
+            X()
 
+    def test_subclass_class(self):
+        generalimport("fakepackage")
+        import fakepackage
 
+        class SubClass(fakepackage.BaseClass):
+            def __init__(self):
+                raise ValueError("'generalimport' should fail earlier with MissingDependencyException")
 
+        self.assertRaises(MissingDependencyException, SubClass)
 
+    def test_subclass_class_direct_new_call(self):
+        generalimport("fakepackage")
+        import fakepackage
 
+        class SubClass(fakepackage.BaseClass):
+            def __init__(self):
+                raise ValueError("'generalimport' should fail earlier with MissingDependencyException")
 
+        with self.assertRaises(MissingDependencyException):
+            SubClass.__new__(SubClass)