Fix dependent_objects when using single table inheritance

sqlalchemy_utils/functions/foreign_keys.py

@@ -4,6 +4,7 @@ from itertools import groupby
 import six
 import sqlalchemy as sa
 from sqlalchemy.engine import reflection
+from sqlalchemy.exc import NoInspectionAvailable
 from sqlalchemy.orm import object_session, mapperlib
 from sqlalchemy.schema import MetaData, Table, ForeignKeyConstraint
 
@@ -195,9 +196,7 @@ def dependent_objects(obj, foreign_keys=None):
     through all dependent objects for given SQLAlchemy object.
 
     Consider a User object is referenced in various articles and also in
-    various orders. Getting all these dependent objects is as easy as:
+    various orders. Getting all these dependent objects is as easy as::
-
-    ::
 
         from sqlalchemy_utils import dependent_objects
 
@@ -219,9 +218,7 @@ def dependent_objects(obj, foreign_keys=None):
     it will lead to nasty IntegrityErrors being raised.
 
     In the following example we delete given user if it doesn't have any
-    foreign key restricted dependent objects.
+    foreign key restricted dependent objects::
-
-    ::
 
 
         from sqlalchemy_utils import get_referencing_foreign_keys
@@ -272,8 +269,17 @@ def dependent_objects(obj, foreign_keys=None):
     classes = obj.__class__._decl_class_registry
 
     for table, keys in group_foreign_keys(foreign_keys):
+        keys = list(keys)
         for class_ in classes.values():
-            if hasattr(class_, '__table__') and class_.__table__ == table:
+            try:
+                mapper = sa.inspect(class_)
+            except NoInspectionAvailable:
+                continue
+            parent_mapper = mapper.inherits
+            if (
+                table in mapper.tables and
+                not (parent_mapper and table in parent_mapper.tables)
+            ):
                 criteria = []
                 visited_constraints = []
                 for key in keys:

tests/functions/test_dependent_objects.py

@@ -153,3 +153,64 @@ class TestDependentObjectsWithCompositeKeys(TestCase):
         assert len(deps) == 2
         assert articles[0] in deps
         assert articles[3] in deps
+
+
+class TestDependentObjectsWithSingleTableInheritance(TestCase):
+    def create_models(self):
+        class Category(self.Base):
+            __tablename__ = 'category'
+            id = sa.Column(sa.Integer, primary_key=True)
+            name = sa.Column(sa.Unicode(255))
+
+        class TextItem(self.Base):
+            __tablename__ = 'text_item'
+            id = sa.Column(sa.Integer, primary_key=True)
+            name = sa.Column(sa.Unicode(255))
+            category_id = sa.Column(
+                sa.Integer,
+                sa.ForeignKey(Category.id)
+            )
+            category = sa.orm.relationship(
+                Category,
+                backref=sa.orm.backref(
+                    'articles'
+                )
+            )
+            type = sa.Column(sa.Unicode(255))
+
+            __mapper_args__ = {
+                'polymorphic_on': type,
+            }
+
+        class Article(TextItem):
+            __mapper_args__ = {
+                'polymorphic_identity': u'article'
+            }
+
+        class BlogPost(TextItem):
+            __mapper_args__ = {
+                'polymorphic_identity': u'blog_post'
+            }
+
+
+        self.Category = Category
+        self.TextItem = TextItem
+        self.Article = Article
+        self.BlogPost = BlogPost
+
+    def test_returns_all_dependent_objects(self):
+        category1 = self.Category(name=u'Category #1')
+        category2 = self.Category(name=u'Category #2')
+        articles = [
+            self.Article(category=category1),
+            self.Article(category=category1),
+            self.Article(category=category2),
+            self.Article(category=category2),
+        ]
+        self.session.add_all(articles)
+        self.session.commit()
+
+        deps = list(dependent_objects(category1))
+        assert len(deps) == 2
+        assert articles[0] in deps
+        assert articles[1] in deps