Use built-in __subclasses__() instead of registering

schematics/models.py

@@ -179,12 +179,6 @@ def set_owner_model(field, klass):
             set_owner_model(field, klass)
             field.name = field_name
 
-        # Register class on ancestor models
-        klass._subclasses = []
-        for base in klass.__mro__[1:]:
-            if isinstance(base, ModelMeta):
-                base._subclasses.append(klass)
-
         return klass
 
     @classmethod

schematics/types/compound.py

@@ -7,6 +7,7 @@
 
 from ..exceptions import ValidationError, ConversionError, ModelValidationError, StopValidation
 from ..transforms import export_loop, EMPTY_LIST, EMPTY_DICT
+
 from .base import BaseType
 
 from six import iteritems
@@ -357,10 +358,7 @@ def find_model(self, data):
         if self.claim_function:
             chosen_class = self.claim_function(self, data)
         else:
-            candidates = self.model_classes
-            if self.allow_subclasses:
-                candidates = itertools.chain.from_iterable(
-                                 ([m] + m._subclasses for m in candidates))
+            candidates = self._get_candidates()
             fallback = None
             matching_classes = []
             for cls in candidates:
@@ -400,5 +398,25 @@ def export_loop(self, model_instance, field_converter,
         elif print_none:
             return shaped
 
+    def _get_candidates(self):
+        candidates = self.model_classes
+
+        if self.allow_subclasses:
+            candidates = itertools.chain.from_iterable(
+                ([m] + get_all_subclasses(m) for m in candidates)
+            )
+
+        return candidates
+
+
+def get_all_subclasses(cls):
+    all_subclasses = []
+
+    for subclass in cls.__subclasses__():
+        all_subclasses.append(subclass)
+        all_subclasses.extend(get_all_subclasses(subclass))
+
+    return all_subclasses
+
 
 from ..models import Model

tests/test_polymodeltype.py

@@ -2,7 +2,7 @@
 
 from schematics.models import Model
 from schematics.types import StringType
-from schematics.types.compound import PolyModelType
+from schematics.types.compound import PolyModelType, get_all_subclasses
 
 
 class A(Model): # fallback model (doesn't define a claim method)
@@ -42,11 +42,13 @@ class Foo(Model):
     cfn    = PolyModelType([B, C], claim_function=claim_func, strict=False)
 
 
-def test_subclass_registry():
+def test_get_all_subclasses():
+    assert A.__subclasses__() == [Aaa, B]
+    assert B.__subclasses__() == [C]
+    assert C.__subclasses__() == []
+
+    assert get_all_subclasses(A) == [Aaa, B, C]
 
-    assert A._subclasses == [Aaa, B, C]
-    assert B._subclasses == [C]
-    assert C._subclasses == []
 
 def test_inheritance_based_polymorphic(): # base
 
@@ -115,4 +117,3 @@ def test_refuse_unrelated_export():
         foo = Foo()
         foo.strict = Aaa()
         foo.to_primitive()
-