Add support for column property in version models

Copy the column_property() defined in the parent model to the
version model

sqlalchemy_continuum/builder.py

@@ -3,6 +3,8 @@
 from functools import wraps
 
 import sqlalchemy as sa
+from sqlalchemy_continuum.expression_reflector import VersionExpressionReflector
+from sqlalchemy_continuum.utils import is_table_column
 from sqlalchemy_utils.functions import get_declarative_base
 
 from .dialects.postgresql import create_versioning_trigger_listeners
@@ -189,6 +191,7 @@ def configure_versioned_classes(self):
         self.build_relationships(pending_classes_copies)
         self.enable_active_history(pending_classes_copies)
         self.create_column_aliases(pending_classes_copies)
+        self.create_column_properties(pending_classes_copies)
 
     def enable_active_history(self, version_classes):
         """
@@ -220,3 +223,23 @@ def create_column_aliases(self, version_classes):
                         continue
 
                     version_class_mapper.add_property(key, sa.orm.column_property(version_class_column))
+
+    def create_column_properties(self, version_classes):
+        """
+        Create equivalent column_property() on the version class (as it is on the parent model)
+
+        This does not handle the simple column aliases - just expressions
+        """
+        for cls in version_classes:
+            model_mapper = sa.inspect(cls)
+            version_class = self.manager.version_class_map.get(cls)
+            if not version_class:
+                continue
+
+            version_class_mapper = sa.inspect(version_class)
+            reflector = VersionExpressionReflector()
+            for key, column in model_mapper.columns.items():
+                if is_table_column(column):  # We ignore simple table columns
+                    continue
+                version_column = reflector(column)
+                version_class_mapper.add_property(key, sa.orm.column_property(version_column))

sqlalchemy_continuum/expression_reflector.py

@@ -5,10 +5,7 @@
 
 
 class VersionExpressionReflector(sa.sql.visitors.ReplacingCloningVisitor):
-    def __init__(self, parent, relationship):
-        self.parent = parent
-        self.relationship = relationship
-
+    """Take an expression and convert the columns to the version_table's columns"""
     def replace(self, column):
         if not isinstance(column, sa.Column):
             return
@@ -18,16 +15,34 @@ def replace(self, column):
             reflected_column = column
         else:
             reflected_column = table.c[column.name]
-            if (
-                column in self.relationship.local_columns and
-                table == self.parent.__table__
-            ):
-                reflected_column = bindparam(
-                    column.key,
-                    getattr(self.parent, column.key)
-                )
 
         return reflected_column
 
     def __call__(self, expr):
         return self.traverse(expr)
+
+
+class RelationshipPrimaryJoinReflector(VersionExpressionReflector):
+    """
+    Takes a relationship and modifies it to handle the primaryjoin of the relationship
+    """
+    def __init__(self, parent, relationship):
+        self.parent = parent
+        self.relationship = relationship
+
+    def replace(self, column):
+        reflected_column = super().replace(column)
+        if reflected_column is None:
+            return
+
+        if (
+            column in self.relationship.local_columns and
+            reflected_column.table == self.parent.__table__
+        ):
+            # Keep the columns from the self.parent.__table__ as is
+            reflected_column = bindparam(
+                column.key,
+                getattr(self.parent, column.key)
+            )
+
+        return reflected_column

sqlalchemy_continuum/relationship_builder.py

@@ -1,7 +1,7 @@
 import sqlalchemy as sa
 
 from .exc import ClassNotVersioned
-from .expression_reflector import VersionExpressionReflector
+from .expression_reflector import RelationshipPrimaryJoinReflector
 from .operation import Operation
 from .table_builder import TableBuilder
 from .utils import adapt_columns, version_class, option
@@ -46,7 +46,7 @@ def one_to_many_subquery(self, obj):
 
     def many_to_one_subquery(self, obj):
         tx_column = option(obj, 'transaction_column_name')
-        reflector = VersionExpressionReflector(obj, self.property)
+        reflector = RelationshipPrimaryJoinReflector(obj, self.property)
 
         return getattr(self.remote_cls, tx_column) == (
             sa.select(
@@ -93,7 +93,7 @@ def criteria(self, obj):
             elif direction.name == 'MANYTOONE':
                 return self.many_to_one_criteria(obj)
         else:
-            reflector = VersionExpressionReflector(obj, self.property)
+            reflector = RelationshipPrimaryJoinReflector(obj, self.property)
             return reflector(self.property.primaryjoin)
 
     def many_to_many_criteria(self, obj):
@@ -171,7 +171,7 @@ def many_to_one_criteria(self, obj):
         AND operation_type != 2
 
         """
-        reflector = VersionExpressionReflector(obj, self.property)
+        reflector = RelationshipPrimaryJoinReflector(obj, self.property)
         return sa.and_(
             reflector(self.property.primaryjoin),
             self.many_to_one_subquery(obj),
@@ -209,7 +209,7 @@ def one_to_many_criteria(self, obj):
         )
 
         """
-        reflector = VersionExpressionReflector(obj, self.property)
+        reflector = RelationshipPrimaryJoinReflector(obj, self.property)
         return sa.and_(
             reflector(self.property.primaryjoin),
             self.one_to_many_subquery(obj),
@@ -263,7 +263,7 @@ def association_subquery(self, obj):
         tx_column = option(obj, 'transaction_column_name')
         join_column = self.property.primaryjoin.right.name
         object_join_column = self.property.primaryjoin.left.name
-        reflector = VersionExpressionReflector(obj, self.property)
+        reflector = RelationshipPrimaryJoinReflector(obj, self.property)
 
         association_table_alias = self.association_version_table.alias()
         association_cols = [

sqlalchemy_continuum/version.py

@@ -1,7 +1,7 @@
 import sqlalchemy as sa
 
 from .reverter import Reverter
-from .utils import get_versioning_manager, is_internal_column, parent_class
+from .utils import get_versioning_manager, is_internal_column, is_table_column, parent_class
 
 
 class VersionClassBase(object):
@@ -52,8 +52,9 @@ def changeset(self):
         previous_version = self.previous
         data = {}
 
-        for key in sa.inspect(self.__class__).columns.keys():
-            if is_internal_column(self, key):
+        for key, column in sa.inspect(self.__class__).columns.items():
+            if is_internal_column(self, key) or not is_table_column(column):
+                # Ignore internal columns and column_property() which are expressions
                 continue
             if not previous_version:
                 old = None

tests/builders/test_model_builder.py

@@ -7,3 +7,16 @@ def test_builds_relationship(self):
 
     def test_parent_has_access_to_versioning_manager(self):
         assert self.Article.__versioning_manager__
+
+
+    def test_column_properties(self):
+        article = self.Article()
+        article.name = u'Name'
+        article.content = u'Content'
+        article.description = u'Desc'
+        self.session.add(article)
+        self.session.commit()
+
+        article_version = article.versions[0]
+        assert article.fulltext_content == article.name + article.content + article.description
+        assert article.fulltext_content == article_version.fulltext_content