fix(#64): cartesian product in reln reflection to non-versioned classes

In many-to-many relationships when one of the classes is not versioned,
we were not including the secondaryjoin in the filter criteria leading
to a cartesian product.

Author: winwinashwin

sqlalchemy_history/relationship_builder.py

@@ -83,7 +83,12 @@ def criteria(self, obj):
                 return self.many_to_one_criteria(obj)
         else:
             reflector = VersionExpressionReflector(obj, self.property)
-            return reflector(self.property.primaryjoin)
+            criteria = reflector(self.property.primaryjoin)
+
+            # For many-to-many relationships, we also need to include the secondary join
+            if direction.name == "MANYTOMANY" and self.property.secondaryjoin is not None:
+                criteria = sa.and_(criteria, reflector(self.property.secondaryjoin))
+            return criteria
 
     def many_to_many_criteria(self, obj):
         """Returns the many-to-many query.

tests/relationships/test_non_versioned_classes.py

@@ -101,3 +101,22 @@ def test_single_insert(self):
         self.session.commit()
         assert len(article.versions[0].tags) == 1
         assert isinstance(article.versions[0].tags[0], self.Tag)
+
+    def test_no_cartesian_product_with_multiple_unrelated_tags(self):
+        # Create an article with one tag
+        article = self.Article(name="Some article")
+        tag1 = self.Tag(name="tag1")
+        article.tags.append(tag1)
+        self.session.add(article)
+        self.session.commit()
+
+        # Create another article with a different tag
+        article2 = self.Article(name="Another article")
+        tag2 = self.Tag(name="tag2")
+        article2.tags.append(tag2)
+        self.session.add(article2)
+        self.session.commit()
+
+        # Ensure the first article's version only has its own tag, not all tags
+        assert len(article.versions[0].tags) == 1
+        assert article.versions[0].tags[0] == tag1