Properly model nullable relationships (#370)

* Fixes [302](#302)

* Disallow mapped_columns for SQLModels codegen

* Disallow mapped_columns for SQLModels codegen

* Ensure SQLModel is installed as part of the test-suite

* PR Fixes

* Update src/sqlacodegen/generators.py

Co-authored-by: Alex Grönholm <[email protected]>

* PR Fixes

* PR Fixes

* Further PR Fixes

* Further PR Fixes

* Further PR Fixes

* Typo fix

* PR FIx

* PR FIx

* Fix Enum rendering

* Fix bad commit

* Added new changes to CHANGES.rst

* Support optional relationships

* Support optional relationships

* Fix all tests

* PR Fixes

* PR Fixes

* Update CHANGES.rst

Co-authored-by: Alex Grönholm <[email protected]>

* Update src/sqlacodegen/generators.py

Co-authored-by: Alex Grönholm <[email protected]>

---------

Co-authored-by: Alex Grönholm <[email protected]>

Author: sheinbergon

CHANGES.rst

@@ -3,6 +3,7 @@ Version history
 
 **UNRELEASED**
 
+- Changed nullable relationships to include ``Optional`` in their type annotations
 - Dropped support for Python 3.8
 - Fixed SQLModel code generation
 - Fixed two rendering issues in ``ENUM`` columns when a non-default schema is used: an

src/sqlacodegen/generators.py

@@ -1306,6 +1306,11 @@ def render_join(terms: list[JoinType]) -> str:
             RelationshipType.MANY_TO_ONE,
         ):
             relationship_type = f"'{relationship.target.name}'"
+            if relationship.constraint and any(
+                col.nullable for col in relationship.constraint.columns
+            ):
+                self.add_literal_import("typing", "Optional")
+                relationship_type = f"Optional[{relationship_type}]"
         elif relationship.type == RelationshipType.MANY_TO_MANY:
             self.add_literal_import("typing", "List")
             relationship_type = f"List['{relationship.target.name}']"

tests/test_generator_dataclass.py

@@ -127,7 +127,7 @@ class SimpleItems(Base):
             container_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('simple_containers.id'))
 
-            container: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
+            container: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers', \
 back_populates='simple_items')
         """,
     )
@@ -237,7 +237,7 @@ class SimpleItems(Base):
             id: Mapped[int] = mapped_column(Integer, primary_key=True)
             container_id: Mapped[Optional[int]] = mapped_column(Integer)
 
-            container: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
+            container: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers', \
 back_populates='simple_items')
         """,
     )

tests/test_generator_declarative.py

@@ -148,7 +148,7 @@ class SimpleItems(Base):
     container_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('simple_containers.id'))
 
-    container: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
+    container: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers', \
 back_populates='simple_items')
     """,
     )
@@ -182,7 +182,7 @@ class SimpleItems(Base):
     parent_item_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('simple_items.id'))
 
-    parent_item: Mapped['SimpleItems'] = relationship('SimpleItems', \
+    parent_item: Mapped[Optional['SimpleItems']] = relationship('SimpleItems', \
 remote_side=[id], back_populates='parent_item_reverse')
     parent_item_reverse: Mapped[List['SimpleItems']] = relationship('SimpleItems', \
 remote_side=[parent_item_id], back_populates='parent_item')
@@ -221,12 +221,12 @@ class SimpleItems(Base):
 mapped_column(ForeignKey('simple_items.id'))
     top_item_id: Mapped[Optional[int]] = mapped_column(ForeignKey('simple_items.id'))
 
-    parent_item: Mapped['SimpleItems'] = relationship('SimpleItems', \
+    parent_item: Mapped[Optional['SimpleItems']] = relationship('SimpleItems', \
 remote_side=[id], foreign_keys=[parent_item_id], back_populates='parent_item_reverse')
     parent_item_reverse: Mapped[List['SimpleItems']] = relationship('SimpleItems', \
 remote_side=[parent_item_id], foreign_keys=[parent_item_id], \
 back_populates='parent_item')
-    top_item: Mapped['SimpleItems'] = relationship('SimpleItems', remote_side=[id], \
+    top_item: Mapped[Optional['SimpleItems']] = relationship('SimpleItems', remote_side=[id], \
 foreign_keys=[top_item_id], back_populates='top_item_reverse')
     top_item_reverse: Mapped[List['SimpleItems']] = relationship('SimpleItems', \
 remote_side=[top_item_id], foreign_keys=[top_item_id], back_populates='top_item')
@@ -289,7 +289,7 @@ class SimpleItems(Base):
     container_id1: Mapped[Optional[int]] = mapped_column(Integer)
     container_id2: Mapped[Optional[int]] = mapped_column(Integer)
 
-    simple_containers: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
+    simple_containers: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers', \
 back_populates='simple_items')
         """,
     )
@@ -301,7 +301,7 @@ def test_onetomany_multiref(generator: CodeGenerator) -> None:
         generator.metadata,
         Column("id", INTEGER, primary_key=True),
         Column("parent_container_id", INTEGER),
-        Column("top_container_id", INTEGER),
+        Column("top_container_id", INTEGER, nullable=False),
         ForeignKeyConstraint(["parent_container_id"], ["simple_containers.id"]),
         ForeignKeyConstraint(["top_container_id"], ["simple_containers.id"]),
     )
@@ -338,12 +338,12 @@ class SimpleItems(Base):
     __tablename__ = 'simple_items'
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
-    parent_container_id: Mapped[Optional[int]] = \
+    top_container_id: Mapped[int] = \
 mapped_column(ForeignKey('simple_containers.id'))
-    top_container_id: Mapped[Optional[int]] = \
+    parent_container_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('simple_containers.id'))
 
-    parent_container: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
+    parent_container: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers', \
 foreign_keys=[parent_container_id], back_populates='simple_items')
     top_container: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
 foreign_keys=[top_container_id], back_populates='simple_items_')
@@ -383,7 +383,7 @@ class OtherItems(Base):
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
 
-    simple_items: Mapped['SimpleItems'] = relationship('SimpleItems', uselist=False, \
+    simple_items: Mapped[Optional['SimpleItems']] = relationship('SimpleItems', uselist=False, \
 back_populates='other_item')
 
 
@@ -394,7 +394,7 @@ class SimpleItems(Base):
     other_item_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('other_items.id'), unique=True)
 
-    other_item: Mapped['OtherItems'] = relationship('OtherItems', \
+    other_item: Mapped[Optional['OtherItems']] = relationship('OtherItems', \
 back_populates='simple_items')
         """,
     )
@@ -437,7 +437,7 @@ class Oglkrogk(Base):
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     fehwiuhfiwID: Mapped[Optional[int]] = mapped_column(ForeignKey('fehwiuhfiw.id'))
 
-    fehwiuhfiw: Mapped['Fehwiuhfiw'] = \
+    fehwiuhfiw: Mapped[Optional['Fehwiuhfiw']] = \
 relationship('Fehwiuhfiw', back_populates='oglkrogk')
         """,
     )
@@ -487,7 +487,7 @@ class SimpleItems(Base):
     container_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('simple_containers.id'))
 
-    container: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
+    container: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers', \
 back_populates='simple_items')
         """,
     )
@@ -531,7 +531,7 @@ class SimpleItems(Base):
     relationship_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('relationship.id'))
 
-    relationship_: Mapped['Relationship'] = relationship('Relationship', \
+    relationship_: Mapped[Optional['Relationship']] = relationship('Relationship', \
 back_populates='simple_items')
         """,
     )
@@ -577,7 +577,7 @@ class SimpleItems(Base):
     container_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('simple_containers.id'))
 
-    container: Mapped['SimpleContainers'] = relationship('SimpleContainers')
+    container: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers')
 """,
     )
 
@@ -994,7 +994,7 @@ class {class_name.capitalize()}(Base):
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
 
-    simple_item: Mapped['SimpleItem'] = relationship('SimpleItem', uselist=False, \
+    simple_item: Mapped[Optional['SimpleItem']] = relationship('SimpleItem', uselist=False, \
 back_populates='{relationship_name}')
 
 
@@ -1005,7 +1005,7 @@ class SimpleItem(Base):
     {relationship_name}_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('{table_name}.id'), unique=True)
 
-    {relationship_name}: Mapped['{class_name.capitalize()}'] = \
+    {relationship_name}: Mapped[Optional['{class_name.capitalize()}']] = \
 relationship('{class_name.capitalize()}', back_populates='simple_item')
         """,
     )
@@ -1117,7 +1117,7 @@ class SimpleItems(Base):
     other_item_id: Mapped[Optional[int]] = \
 mapped_column(ForeignKey('otherschema.other_items.id'))
 
-    other_item: Mapped['OtherItems'] = relationship('OtherItems', \
+    other_item: Mapped[Optional['OtherItems']] = relationship('OtherItems', \
 back_populates='simple_items')
         """,
     )
@@ -1472,7 +1472,7 @@ class SimpleItems(Base):
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     container_id: Mapped[Optional[int]] = mapped_column(Integer)
 
-    container: Mapped['SimpleContainers'] = relationship('SimpleContainers', \
+    container: Mapped[Optional['SimpleContainers']] = relationship('SimpleContainers', \
 back_populates='simple_items')
 """,
     )